k-office: initial code dumpk-office/init

30 files changed, 2220 insertions, 0 deletions

diff --git a/apps/koffice/.gitignore b/apps/koffice/.gitignore
new file mode 100644
index 000000000000..eb5a316cbd19
--- /dev/null
+++ b/apps/koffice/.gitignore
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diff --git a/apps/koffice/Cargo.lock b/apps/koffice/Cargo.lock
new file mode 100644
index 000000000000..f79c22086be3
--- /dev/null
+++ b/apps/koffice/Cargo.lock
@@ -0,0 +1,433 @@
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diff --git a/apps/koffice/Cargo.toml b/apps/koffice/Cargo.toml
new file mode 100644
index 000000000000..4ff3f0a91819
--- /dev/null
+++ b/apps/koffice/Cargo.toml
@@ -0,0 +1,5 @@
+[workspace]
+members = [
+  "libko",
+  "invoice"
+]
\ No newline at end of file
diff --git a/apps/koffice/README.md b/apps/koffice/README.md
new file mode 100644
index 000000000000..2e37820450a6
--- /dev/null
+++ b/apps/koffice/README.md
@@ -0,0 +1,25 @@
+# k-office
+
+A set of plain-text, free software tools to run a small business.
+
+
+## Set of tools
+
+Currently k-office consists of the following tools.  A support library
+`libko` provides the basic building blocks for other tools.
+
+- cassiopeia -- a plain-text time tracking tool
+- invoice -- a LaTeX template based invoice generator
+
+
+## How to build
+
+Build files for the whole suite are provided in [`nix/`](./nix/).  You
+can also build individual tools (e.g. to hack on) via Cargo.
+
+
+## Contributions
+
+If you want to make suggestions, or send a patch in you can do so via
+my public inbox.  Either send the patches directly, or via a
+request-pull!
diff --git a/apps/koffice/invoice/Cargo.toml b/apps/koffice/invoice/Cargo.toml
new file mode 100644
index 000000000000..15bb8e7e90c6
--- /dev/null
+++ b/apps/koffice/invoice/Cargo.toml
@@ -0,0 +1,13 @@
+[package]
+name = "invoice"
+version = "0.2.0"
+authors = ["Katharina Fey <kookie@spacekookie.de>"]
+edition = "2018"
+
+[dependencies]
+chrono = { version = "0.4", features = [ "serde" ] }
+clap = { version = "2.0", features = [ "wrap_help", "color", "suggestions" ] }
+libko = { path = "../libko", version = "*" }
+serde = { version = "1.0", features = [ "derive" ] }
+env_logger = "0.8"
+log = "0.4"
\ No newline at end of file
diff --git a/apps/koffice/invoice/src/base.rs b/apps/koffice/invoice/src/base.rs
new file mode 100644
index 000000000000..a29af6480bf8
--- /dev/null
+++ b/apps/koffice/invoice/src/base.rs
@@ -0,0 +1,20 @@
+//! Basing application initialisation
+
+use libko::*;
+use std::path::PathBuf;
+
+pub fn init(pid: Option<&str>, tf: Option<&str>, t: Option<&str>, rev: Option<&str>) -> Meta {
+    let mut meta = initialise();
+
+    meta.project_id = pid.map(Into::into);
+
+    if let Some(tfpath) = tf {
+        meta.load_timefile(tfpath);
+    }
+
+    if let Some(template) = t {
+        meta.template = Some(PathBuf::new().join(template));
+    }
+
+    dbg!(meta)
+}
diff --git a/apps/koffice/invoice/src/cli.rs b/apps/koffice/invoice/src/cli.rs
new file mode 100644
index 000000000000..cbf27efe6cc4
--- /dev/null
+++ b/apps/koffice/invoice/src/cli.rs
@@ -0,0 +1,76 @@
+use crate::Meta;
+use clap::{App, AppSettings, Arg, SubCommand};
+
+pub struct AppState {
+    pub meta: Meta,
+    pub cmd: Command,
+}
+
+pub enum Command {
+    Init,
+    Generate,
+    Install,
+}
+
+pub fn parse() -> AppState {
+    let project_id =
+        Arg::with_name("project id").help("The project identifier.  Format: [client/]<project>");
+
+    let timefile = Arg::with_name("timefile")
+        .help("Location of the project's time file")
+        .takes_value(true)
+        .long("file")
+        .short("f")
+        .default_value("./time.cass");
+
+    let template = Arg::with_name("template")
+        .help("Override the default application template")
+        .long("templ")
+        .short("t")
+        .takes_value(true)
+        .default_value("$XDG_CONFIG_HOME/k-office/template.tex");
+
+    let revision = Arg::with_name("revision")
+        .help("Override the default revision system")
+        .long("rev")
+        .short("r")
+        .takes_value(true);
+
+    let app = App::new("invoice")
+        .version(env!("CARGO_PKG_VERSION"))
+        .about("A k-office tool to generate and manage invoices")
+        .settings(&[
+            AppSettings::SubcommandRequired,
+            AppSettings::GlobalVersion,
+            AppSettings::ColoredHelp,
+            AppSettings::DontCollapseArgsInUsage,
+        ])
+        .subcommand(
+            SubCommand::with_name("init")
+                .about("Initialise a new invoice config")
+                .arg(timefile)
+                .arg(revision.clone()),
+        )
+        .subcommand(
+            SubCommand::with_name("generate")
+                .about("Generate an invoice PDF for a client/ project based on a template")
+                .arg(revision)
+                .arg(template),
+        );
+
+    let matches = app.get_matches();
+
+    let project_id = matches.value_of("project id");
+    let timefile = matches.value_of("timefile");
+    let template = matches.value_of("template");
+    let revision = matches.value_of("revision");
+
+    AppState {
+        meta: crate::base::init(project_id, timefile, template, revision),
+        cmd: match matches.subcommand() {
+            ("init", _) => Command::Init,
+            ("generate", _) => Command::Generate,
+            _ => unreachable!(),
+        },
+    }
+}
diff --git a/apps/koffice/invoice/src/main.rs b/apps/koffice/invoice/src/main.rs
new file mode 100644
index 000000000000..742b74be0b0a
--- /dev/null
+++ b/apps/koffice/invoice/src/main.rs
@@ -0,0 +1,41 @@
+
+mod base;
+mod cli;
+mod pfile;
+
+pub(crate) use base::*;
+pub(crate) use cli::*;
+pub(crate) use pfile::*;
+
+use libko::*;
+use std::{io::Write, fs::OpenOptions as Oo};
+
+fn main() {
+    let AppState { meta, cmd } = cli::parse();
+
+    match cmd {
+        Command::Init => init(meta),
+        Command::Generate => generate(meta),
+        Command::Install => todo!(),
+    }
+}
+
+fn init(meta: Meta) {
+    let pid = meta.project_id.as_ref().unwrap_or_else(|| {
+        meta.timefile
+            .as_ref()
+            .expect("No project id given, with no timefile available")
+            .client()
+            .as_ref()
+            .unwrap()
+    });
+
+    let path = meta.invoice_dir.join(pid);
+    let mut f = Oo::new().write(true).truncate(true).open(path).unwrap();
+    f.write_all(pfile::data_templ().as_bytes()).unwrap();
+    
+    // let pid = meta.project_id.as_ref().unwrap_or_else(||
+    // let f = meta.invoice_dir.join(meta.project_id);
+}
+
+fn generate(meta: Meta) {}
diff --git a/apps/koffice/invoice/src/pfile.rs b/apps/koffice/invoice/src/pfile.rs
new file mode 100644
index 000000000000..ec99e5ab3049
--- /dev/null
+++ b/apps/koffice/invoice/src/pfile.rs
@@ -0,0 +1,33 @@
+use crate::{Account, Address, Worker, InvoiceId};
+use chrono::NaiveDate;
+use serde::{Serialize, Deserialize};
+
+/// Describes invoice metadata
+#[derive(Serialize, Deserialize)]
+pub struct InvoiceFile {
+    invoice_id: InvoiceId,
+    date: NaiveDate,
+    author: Worker,
+    account: Account,
+    client: Address,
+    vat: u8,
+    service: Vec<ServiceEntry>,
+    currency: String,
+    lang: String,
+}
+
+/// A service description
+#[derive(Serialize, Deserialize)]
+pub enum ServiceEntry {
+    Line(String),
+    Hash {
+        description: String,
+        price: usize,
+        details: Vec<String>,
+    }
+}
+
+pub fn data_templ() -> String {
+
+    todo!()
+}
diff --git a/apps/koffice/libko/Cargo.lock b/apps/koffice/libko/Cargo.lock
new file mode 100644
index 000000000000..bcc14cca627a
--- /dev/null
+++ b/apps/koffice/libko/Cargo.lock
@@ -0,0 +1,189 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "autocfg"
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+ "libc",
+ "num-integer",
+ "num-traits",
+ "serde",
+ "time",
+ "winapi",
+]
+
+[[package]]
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+
+[[package]]
+name = "libko"
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+ "chrono",
+ "serde",
+ "serde_yaml",
+ "xdg",
+]
+
+[[package]]
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+]
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+ "serde",
+ "yaml-rust",
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+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
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+
+[[package]]
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+
+[[package]]
+name = "yaml-rust"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "56c1936c4cc7a1c9ab21a1ebb602eb942ba868cbd44a99cb7cdc5892335e1c85"
+dependencies = [
+ "linked-hash-map",
+]
diff --git a/apps/koffice/libko/Cargo.toml b/apps/koffice/libko/Cargo.toml
new file mode 100644
index 000000000000..44a62071c07d
--- /dev/null
+++ b/apps/koffice/libko/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "libko"
+version = "1.0.0"
+authors = ["Katharina Fey <kookie@spacekookie.de>"]
+edition = "2018"
+
+[dependencies]
+chrono = { version = "0.4", features = [ "serde" ] }
+serde = { version = "1.0", features = [ "derive" ] }
+serde_yaml = "*"
+xdg = "2.2.0"
+logos = "0.11"
\ No newline at end of file
diff --git a/apps/koffice/libko/src/cass/data.rs b/apps/koffice/libko/src/cass/data.rs
new file mode 100644
index 000000000000..4ff4dc93020e
--- /dev/null
+++ b/apps/koffice/libko/src/cass/data.rs
@@ -0,0 +1,116 @@
+//! Typed time file for cassiopeia
+//!
+//! This data gets generated by the `format` module, and can later be
+//! used to generate new files, and perform various lookups and
+//! analysis tasks.
+
+use crate::cass::{
+    error::{ParseError, ParseResult, UserResult},
+    format::ir::{IrItem, IrType, MakeIr},
+    timeline::{Entry, Timeline},
+    Date, Time,
+};
+use chrono::{DateTime, Duration, FixedOffset as Offset, Local, NaiveDate};
+use std::collections::BTreeMap;
+
+#[derive(Clone, Debug, Default)]
+pub struct TimeFile {
+    /// A parsed header structure
+    pub(crate) header: BTreeMap<String, String>,
+    /// A parsed timeline of events
+    pub(crate) timeline: Timeline,
+}
+
+impl TimeFile {
+    pub fn project(&self) -> Option<&String> {
+        self.header.get("project")
+    }
+
+    pub fn client(&self) -> Option<&String> {
+        self.header.get("client")
+    }
+    
+    /// Append entries to the timeline from the parsed IR
+    ///
+    /// Report any errors that occur back to the parser, that will
+    /// print a message to the user and terminate the program.
+    pub(crate) fn append(&mut self, line: IrItem) -> ParseResult<()> {
+        match line {
+            IrItem {
+                tt: IrType::Header(ref header),
+                ..
+            } => Ok(header.iter().for_each(|(k, v)| {
+                self.header.insert(k.clone(), v.clone());
+            })),
+            IrItem {
+                tt: IrType::Start(time),
+                lo,
+            } => Ok(self.timeline.start(time).map(|_| ())?),
+            IrItem {
+                tt: IrType::Stop(time),
+                lo,
+            } => Ok(self.timeline.stop(time).map(|_| ())?),
+            IrItem {
+                tt: IrType::Invoice(date),
+                lo,
+            } => Ok(self.timeline.invoice(date).map(|_| ())?),
+            _ => Err(ParseError::Unknown),
+        }
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Session {
+    start: Time,
+    stop: Option<Time>,
+}
+
+impl Session {
+    /// Create a new session with a start time
+    pub(crate) fn start(start: Time) -> Self {
+        Self { start, stop: None }
+    }
+
+    /// Finalise a session with a stop time
+    pub(crate) fn stop(&mut self, stop: Time) {
+        self.stop = Some(stop);
+    }
+
+    /// Check whether this session was already finished
+    pub fn finished(&self) -> bool {
+        self.stop.is_some()
+    }
+
+    /// Get the length of the session, if it was already finished
+    pub fn length(&self) -> Option<Duration> {
+        self.stop.as_ref().map(|stop| stop - &self.start)
+    }
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Invoice {
+    pub(crate) date: Date,
+}
+
+impl Invoice {
+    pub(crate) fn new(date: Date) -> Self {
+        Self { date }
+    }
+}
+
+/// Changes to the timeline are encoded in a delta
+pub enum Delta {
+    Start(Time),
+    Stop(Time),
+    Invoice(Date),
+}
+
+impl MakeIr for Delta {
+    fn make_ir(&self) -> IrType {
+        match self {
+            Self::Start(ref time) => IrType::Start(time.clone()),
+            Self::Stop(ref time) => IrType::Stop(time.clone()),
+            Self::Invoice(ref date) => IrType::Invoice(date.clone()),
+        }
+    }
+}
diff --git a/apps/koffice/libko/src/cass/date.rs b/apps/koffice/libko/src/cass/date.rs
new file mode 100644
index 000000000000..e35b2a96f0f0
--- /dev/null
+++ b/apps/koffice/libko/src/cass/date.rs
@@ -0,0 +1,32 @@
+use crate::cass::Time;
+use chrono::{FixedOffset as Offset, NaiveDate};
+
+/// A convenienc wrapper around [chrono::NaiveDate](chrono::NaiveDate)
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Date {
+    inner: NaiveDate,
+}
+
+impl Date {
+    pub fn today() -> Self {
+        Self::from(Time::now().date())
+    }
+
+    pub(crate) fn from(d: chrono::Date<Offset>) -> Self {
+        Self {
+            inner: d.naive_local(),
+        }
+    }
+}
+
+impl From<NaiveDate> for Date {
+    fn from(inner: NaiveDate) -> Self {
+        Self { inner }
+    }
+}
+
+impl ToString for Date {
+    fn to_string(&self) -> String {
+        format!("{}", self.inner.format("%Y-%m-%d"))
+    }
+}
diff --git a/apps/koffice/libko/src/cass/error.rs b/apps/koffice/libko/src/cass/error.rs
new file mode 100644
index 000000000000..24bbb4965494
--- /dev/null
+++ b/apps/koffice/libko/src/cass/error.rs
@@ -0,0 +1,91 @@
+//! A set of error types for cassiopeia
+
+use std::fmt::{self, Display, Formatter};
+use std::{error::Error, io};
+
+/// User errors that can occur when using cassiopeia
+///
+/// None of these errors are the fault of the program, but rather
+/// fault of the user for giving invalid commands.  They must never
+/// make the program crash, but instead need to print human friendly
+/// error messages.
+#[derive(Debug)]
+pub enum UserError {
+    /// Trying to start a session when one exists
+    ActiveSessionExists,
+    /// Trying to stop a session when none exists
+    NoActiveSession,
+    /// Trying to create a second invoice on the same day
+    SameDayInvoice,
+    /// No work was done since the last invoice
+    NoWorkInvoice,
+}
+
+impl Display for UserError {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "You're doing it wrong!")
+    }
+}
+
+impl Error for UserError {}
+
+pub type UserResult<T> = Result<T, UserError>;
+
+/// Errors that occur when parsing a file
+///
+/// These errors can pre-maturely terminate the run of the program,
+/// but must print a detailed error about what is wrong.  Also,
+/// because they are technically a superset of
+/// [`UserError`](self::UserError), one of the variants is an embedded
+/// user error.
+#[derive(Debug)]
+pub enum ParseError {
+    /// An embedded user error
+    ///
+    /// This error means that the structure of the parsed file is
+    /// wrong, with an invalid sequence of events expressed
+    User(UserError),
+    /// The requested file did not exist
+    NoSuchFile,
+    /// The file could not be read
+    BadPermissions,
+    /// The file could not be written to
+    FileNotWritable,
+    /// Other file related errors
+    FileUnknown(String),
+    /// An invalid keyword was found
+    BadKeyword { line: usize, tokn: String },
+    /// A bad timestamp was found
+    BadTimestamp { line: usize, tokn: String },
+    /// A bad date was found
+    BadDate { line: usize, tokn: String },
+    /// An unknown parse error occured
+    Unknown,
+}
+
+impl Display for ParseError {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        write!(f, "The parsed file was bad :(")
+    }
+}
+
+impl Error for ParseError {}
+
+pub type ParseResult<T> = Result<T, ParseError>;
+
+impl From<UserError> for ParseError {
+    fn from(user: UserError) -> Self {
+        ParseError::User(user)
+    }
+}
+
+impl From<io::Error> for ParseError {
+    fn from(e: io::Error) -> Self {
+        use io::ErrorKind::*;
+        match e.kind() {
+            NotFound => Self::NoSuchFile,
+            PermissionDenied => Self::BadPermissions,
+            _ => Self::FileUnknown(format!("{}", e)),
+        }
+    }
+}
diff --git a/apps/koffice/libko/src/cass/format/gen.rs b/apps/koffice/libko/src/cass/format/gen.rs
new file mode 100644
index 000000000000..f77bcdc90e84
--- /dev/null
+++ b/apps/koffice/libko/src/cass/format/gen.rs
@@ -0,0 +1,32 @@
+//! Cassiopeia line generator
+//!
+//! This module takes a set of IR lines, and generates strings from
+//! them that are in accordance with the way that the parser of the
+//! same version expects them.
+
+use crate::cass::format::ir::{IrItem, IrType};
+
+/// Take a line of IR and generate a string to print into a file
+pub(crate) fn line(ir: &IrItem) -> String {
+    let IrItem { tt, lo } = ir;
+    match tt {
+        IrType::Ignore => "".into(),
+        IrType::Header(map) => format!(
+            "HEADER {}",
+            map.iter()
+                .map(|(k, v)| format!("{}={},", k, v))
+                .collect::<Vec<_>>()
+                .join("")
+        ),
+        IrType::Start(time) => format!("START {}", time.to_string()),
+
+        // FIXME: find a better way to align the lines here rather
+        // than having to manually having to pad the 'STOP' commands
+        IrType::Stop(time) => format!("STOP  {}", time.to_string()),
+        IrType::Invoice(date) => format!("INVOICE {}", date.to_string()),
+    }
+}
+
+pub(crate) fn head_comment() -> String {
+    ";; generated by cassiopeia, be careful about editing by hand!".into()
+}
diff --git a/apps/koffice/libko/src/cass/format/ir.rs b/apps/koffice/libko/src/cass/format/ir.rs
new file mode 100644
index 000000000000..d1a3a62c1508
--- /dev/null
+++ b/apps/koffice/libko/src/cass/format/ir.rs
@@ -0,0 +1,99 @@
+use crate::cass::{format::LineCfg, Date, Time, TimeFile};
+use std::collections::BTreeMap;
+
+/// A set of IR parsed items that makes up a whole cass file
+pub(crate) type IrStream = Vec<IrItem>;
+
+/// Intermediate representation for parsing and generating files
+///
+/// The CASS IR is largely based on the output of the parser's
+/// [`LineCfg`](crate::format::LineCfg), but with concrete types used
+/// in the data layer (namely [`Date`][date] and [`Time`][time]),
+/// while also keeping track of the line numbers to allow idempotent
+/// file changes.
+///
+/// Something not yet implemented is comment pass-through (this needs
+/// to happen in the parser first), but will likely be implemented in
+/// a future version.
+///
+/// [date]: crate::Date
+/// [time]: crate::Time
+#[derive(Debug, Clone)]
+pub(crate) struct IrItem {
+    pub(crate) tt: IrType,
+    pub(crate) lo: usize,
+}
+
+/// Disambiguate between different IR line types with their payload
+#[derive(Debug, Clone)]
+pub(crate) enum IrType {
+    /// A line with parsed header information
+    Header(BTreeMap<String, String>),
+    /// Start a session at a given timestapm
+    Start(Time),
+    /// Stop a session at a given timestamp
+    Stop(Time),
+    /// Invoice a block of previous work
+    Invoice(Date),
+    /// An item that gets ignored
+    Ignore,
+}
+
+/// Generate a stream of IR items from the raw parser output
+pub(crate) fn generate_ir(buf: impl Iterator<Item = LineCfg>) -> IrStream {
+    buf.enumerate().fold(vec![], |mut buf, (lo, item)| {
+        #[cfg_attr(rustfmt, rustfmt_skip)]
+        buf.push(match item {
+            LineCfg::Header(map) => IrItem { tt: IrType::Header(map.into_iter().map(|(k, v)| (k, v.replace(",", ""))).collect()), lo },
+            LineCfg::Start(Some(time)) => IrItem { tt: IrType::Start(time.into()), lo },
+            LineCfg::Stop(Some(time)) => IrItem { tt: IrType::Stop(time.into()), lo },
+            LineCfg::Invoice(Some(date)) => IrItem { tt: IrType::Invoice(date.into()), lo },
+            LineCfg::Ignore => IrItem { tt: IrType::Ignore, lo },
+            _ => IrItem { tt: IrType::Ignore, lo },
+        });
+
+        buf
+    })
+}
+
+pub(crate) trait MakeIr {
+    /// Make a new IR line from an object
+    fn make_ir(&self) -> IrType;
+}
+
+pub(crate) fn clean_ir(ir: &mut IrStream) {
+    ir.remove(0); // FIXME: this is required to remove the leading
+                  // comment, which will be manually re-generated at
+                  // the moment, but which would just add more blank
+                  // lines between the new comment, and the first line
+                  // in this current format.  This is very bad, yikes
+                  // yikes yikes, but what can I do, I have a deadline
+                  // (not really) lol
+
+    // FIXME: this hack gets rid of a trailing empty line if it exists
+    // to make sure we don't have any gaps between work sessions.
+    if match ir.last() {
+        Some(IrItem {
+            tt: IrType::Ignore, ..
+        }) => true,
+        _ => false,
+    } {
+        ir.pop();
+    }
+}
+
+/// Taken an IrType and append it to an existing IR stream
+pub(crate) fn append_ir(ir: &mut IrStream, tt: IrType) {
+    let lo = ir.last().unwrap().lo;
+    ir.push(IrItem { tt, lo });
+}
+
+/// Search for the header that contains the version string and update it
+pub(crate) fn update_header(ir: &mut IrStream) {
+    ir.iter_mut().for_each(|item| match item.tt {
+        IrType::Header(ref mut map) if map.contains_key("version") => {
+            map.insert("version".into(), crate::cass::meta::VERSION.into());
+        }
+        _ => {}
+    });
+}
diff --git a/apps/koffice/libko/src/cass/format/lexer.rs b/apps/koffice/libko/src/cass/format/lexer.rs
new file mode 100644
index 000000000000..bdb89f5180e5
--- /dev/null
+++ b/apps/koffice/libko/src/cass/format/lexer.rs
@@ -0,0 +1,151 @@
+//! Cassiopeia file lexer
+
+use logos::{Lexer, Logos};
+use std::iter::Iterator;
+
+/// A basic line lexer type
+///
+/// This lexer distinguishes between comments, and keyword lines.  It
+/// does not attempt to parse the line specifics.  This is what the
+/// content lexer is for.
+#[derive(Logos, Debug, PartialEq)]
+pub(crate) enum Token {
+    #[token("HEADER")]
+    Header,
+
+    #[token("START")]
+    Start,
+
+    #[token("STOP")]
+    Stop,
+
+    #[token("INVOICE")]
+    Invoice,
+
+    #[regex(r"\w+=[^,$]+[,$]")]
+    HeaderData,
+
+    // FIXME: this will have a leading whitespace that we could remove
+    // with ^\w, but logos does not support this at the moment
+    #[regex(r"[0-9-:+ ]+")]
+    Date,
+
+    #[token(" ", logos::skip)]
+    Space,
+
+    #[regex(";;.*")]
+    Comment,
+
+    #[error]
+    Error,
+}
+
+/// A single token type on a line
+#[derive(Debug)]
+pub(crate) struct LineToken<'l> {
+    pub(crate) tt: Token,
+    pub(crate) slice: &'l str,
+}
+
+/// A lexer wrapped for a single line
+pub(crate) struct LineLexer<'l> {
+    lexer: Lexer<'l, Token>,
+}
+
+impl<'l> LineLexer<'l> {
+    pub(crate) fn get_all(self) -> Vec<LineToken<'l>> {
+        let mut acc = vec![];
+        for l in self {
+            acc.push(l);
+        }
+        acc
+    }
+}
+
+impl<'l> Iterator for LineLexer<'l> {
+    type Item = LineToken<'l>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.lexer.next().map(|tt| Self::Item {
+            tt,
+            slice: self.lexer.slice(),
+        })
+    }
+}
+
+/// Take a line of input and lex it into a stream of tokens
+pub(crate) fn lex<'l>(line: &'l mut String) -> LineLexer<'l> {
+    LineLexer {
+        lexer: Token::lexer(line),
+    }
+}
+
+#[test]
+fn basic_header() {
+    let mut lex = Token::lexer("HEADER version=0.0.0,location=Berlin Lichtenberg,");
+
+    assert_eq!(lex.next(), Some(Token::Header));
+    assert_eq!(lex.span(), 0..6);
+    assert_eq!(lex.slice(), "HEADER");
+
+    assert_eq!(lex.next(), Some(Token::HeaderData));
+    assert_eq!(lex.span(), 7..21);
+    assert_eq!(lex.slice(), "version=0.0.0,");
+
+    assert_eq!(lex.next(), Some(Token::HeaderData));
+    assert_eq!(lex.span(), 21..49);
+    assert_eq!(lex.slice(), "location=Berlin Lichtenberg,");
+
+    assert_eq!(lex.next(), None);
+}
+
+#[test]
+fn basic_start() {
+    let mut lex = Token::lexer("START 2020-11-11 13:00:00+01:00");
+
+    assert_eq!(lex.next(), Some(Token::Start));
+    assert_eq!(lex.span(), 0..5);
+    assert_eq!(lex.slice(), "START");
+
+    assert_eq!(lex.next(), Some(Token::Date));
+    assert_eq!(lex.span(), 5..31);
+    assert_eq!(lex.slice(), " 2020-11-11 13:00:00+01:00");
+
+    assert_eq!(lex.next(), None);
+}
+
+#[test]
+fn basic_stop() {
+    let mut lex = Token::lexer("STOP 2020-11-11 13:00:00+01:00");
+
+    assert_eq!(lex.next(), Some(Token::Stop));
+    assert_eq!(lex.span(), 0..4);
+    assert_eq!(lex.slice(), "STOP");
+
+    assert_eq!(lex.next(), Some(Token::Date));
+    assert_eq!(lex.span(), 4..30);
+    assert_eq!(lex.slice(), " 2020-11-11 13:00:00+01:00");
+
+    assert_eq!(lex.next(), None);
+}
+
+#[test]
+fn basic_invoice() {
+    let mut lex = Token::lexer("INVOICE 2020-11-11 13:00:00+01:00");
+
+    assert_eq!(lex.next(), Some(Token::Invoice));
+    assert_eq!(lex.span(), 0..7);
+    assert_eq!(lex.slice(), "INVOICE");
+
+    assert_eq!(lex.next(), Some(Token::Date));
+    assert_eq!(lex.span(), 7..33);
+    assert_eq!(lex.slice(), " 2020-11-11 13:00:00+01:00");
+
+    assert_eq!(lex.next(), None);
+}
+
+#[test]
+fn basic_comment() {
+    let mut lex = Token::lexer(";; This file is auto generated!");
+    assert_eq!(lex.next(), Some(Token::Comment));
+}
diff --git a/apps/koffice/libko/src/cass/format/mod.rs b/apps/koffice/libko/src/cass/format/mod.rs
new file mode 100644
index 000000000000..2983653898b6
--- /dev/null
+++ b/apps/koffice/libko/src/cass/format/mod.rs
@@ -0,0 +1,76 @@
+//! cassiopeia file format
+
+mod gen;
+pub(crate) mod ir;
+mod lexer;
+mod parser;
+
+pub(crate) use lexer::{LineLexer, LineToken, Token};
+pub(crate) use parser::LineCfg;
+
+use crate::{
+    cass::error::{ParseError, ParseResult},
+    cass::TimeFile,
+};
+use ir::{IrItem, IrStream};
+use std::{
+    fs::{File, OpenOptions},
+    io::{Read, Write},
+};
+
+/// A crate internal representation of the IR stream and timefile
+#[derive(Default)]
+pub(crate) struct ParseOutput {
+    pub(crate) ir: IrStream,
+    pub(crate) tf: TimeFile,
+}
+
+impl ParseOutput {
+    fn append(mut self, ir: IrItem) -> ParseResult<Self> {
+        self.tf.append(ir.clone())?;
+        self.ir.push(ir);
+        Ok(self)
+    }
+}
+
+/// Load a file from disk and parse it into a
+/// [`TimeFile`](crate::TimeFile)
+pub(crate) fn load_file(path: &str) -> ParseResult<ParseOutput> {
+    // Load the raw file contents
+    let mut f = File::open(path)?;
+    let mut content = String::new();
+    f.read_to_string(&mut content)?;
+
+    // Split the file by lines - .cass is a line based format
+    let mut lines: Vec<String> = content.split("\n").map(|l| l.to_owned()).collect();
+
+    // Build an iterator over parsed lines
+    let parsed = lines
+        .iter_mut()
+        .map(|line| lexer::lex(line))
+        .map(|lex| parser::parse(lex));
+
+    // Generate the IR from parse output, then build the timefile
+    ir::generate_ir(parsed)
+        .into_iter()
+        .fold(Ok(ParseOutput::default()), |out, ir| match out {
+            Ok(out) => out.append(ir),
+            e @ Err(_) => e,
+        })
+}
+
+/// Write a file with the updated IR stream
+pub(crate) fn write_file(path: &str, ir: &mut IrStream) -> ParseResult<()> {
+    ir::update_header(ir);
+    let mut lines = ir.into_iter().map(|ir| gen::line(ir)).collect::<Vec<_>>();
+    lines.insert(0, gen::head_comment());
+
+    // let mut f = OpenOptions::new()
+    //     .write(true)
+    //     .create(true)
+    //     .truncate(true)
+    //     .open(path)
+    //     .ok()?;
+    // f.write_all(lines.join("\n").as_bytes()).ok()?;
+    Ok(())
+}
diff --git a/apps/koffice/libko/src/cass/format/parser.rs b/apps/koffice/libko/src/cass/format/parser.rs
new file mode 100644
index 000000000000..8e0602d440d2
--- /dev/null
+++ b/apps/koffice/libko/src/cass/format/parser.rs
@@ -0,0 +1,73 @@
+//! cassiopeia parser
+//!
+//! Takes a lexer's token stream as an input, and outputs a fully
+//! parsed time file.
+
+use crate::cass::format::{LineLexer, LineToken, Token};
+use chrono::{DateTime, FixedOffset as Offset, NaiveDate};
+use std::collections::BTreeMap;
+use std::iter::Iterator;
+
+/// A type-parsed line in a time file
+#[derive(Debug)]
+pub enum LineCfg {
+    /// A header line with a set of keys and values
+    Header(BTreeMap<String, String>),
+    /// A session start line with a date and time
+    Start(Option<DateTime<Offset>>),
+    /// A session stop line with a date and time
+    Stop(Option<DateTime<Offset>>),
+    /// An invoice line with a date
+    Invoice(Option<NaiveDate>),
+    /// A temporary value that is invalid
+    #[doc(hidden)]
+    Ignore,
+}
+
+pub(crate) fn parse<'l>(lex: LineLexer<'l>) -> LineCfg {
+    use LineCfg::*;
+    use Token as T;
+
+    #[cfg_attr(rustfmt, rustfmt_skip)]
+    lex.get_all().into_iter().fold(Ignore, |cfg, tok| match (cfg, tok) {
+        // If the first token is a comment, we ignore it
+        (Ignore, LineToken { tt: T::Comment, .. }, ) => Ignore,
+        // If the first token is a keyword, we wait for more data
+        (Ignore, LineToken { tt: T::Header, .. }) => Header(Default::default()),
+        (Ignore, LineToken { tt: T::Start, .. }) => Start(None),
+        (Ignore, LineToken { tt: T::Stop, .. }) => Stop(None),
+        (Ignore, LineToken { tt: T::Invoice, .. }) => Invoice(None),
+
+        // If the first token _was_ a keyword, fill in the data
+        (Header(map), LineToken { tt: T::HeaderData, slice }) => Header(append_data(map, slice)),
+        (Start(_), LineToken { tt: T::Date, slice }) => Start(parse_datetime(slice)),
+        (Stop(_), LineToken { tt: T::Date, slice }) => Stop(parse_datetime(slice)),
+        (Invoice(_), LineToken { tt: T::Date, slice }) => Invoice(parse_date(slice)),
+
+        // Pass empty lines through,
+        (empty, _) => empty,
+
+        // Ignore everything else (which will be filtered)
+        _ => Ignore,
+    })
+}
+
+fn append_data(mut map: BTreeMap<String, String>, slice: &str) -> BTreeMap<String, String> {
+    let split = slice.split("=").collect::<Vec<_>>();
+    map.insert(split[0].into(), split[1].into());
+    map
+}
+
+fn parse_datetime(slice: &str) -> Option<DateTime<Offset>> {
+    Some(
+        DateTime::parse_from_str(slice, "%Y-%m-%d %H:%M:%S%:z")
+            .expect("Failed to parse date; invalid format!"),
+    )
+}
+
+fn parse_date(slice: &str) -> Option<NaiveDate> {
+    Some(
+        NaiveDate::parse_from_str(slice, "%Y-%m-%d")
+            .expect("Failed to parse date; invalid format!"),
+    )
+}
diff --git a/apps/koffice/libko/src/cass/meta.rs b/apps/koffice/libko/src/cass/meta.rs
new file mode 100644
index 000000000000..ec71498986e3
--- /dev/null
+++ b/apps/koffice/libko/src/cass/meta.rs
@@ -0,0 +1,46 @@
+//! Metadata and strings for this application
+// TODO: translate this
+
+pub const NAME: &'static str = env!("CARGO_PKG_NAME");
+pub const VERSION: &'static str = env!("CARGO_PKG_VERSION");
+pub const AUTHOR: &'static str = env!("CARGO_PKG_AUTHORS");
+pub const ABOUT: &'static str = env!("CARGO_PKG_DESCRIPTION");
+
+pub const ARG_FILE: &'static str = "CASS_FILE";
+pub const ARG_FILE_ABOUT: &'static str = "Provide a .cass file to operate on";
+
+pub const CMD_START: &'static str = "start";
+pub const CMD_START_ABOUT: &'static str = "Start a work session";
+
+pub const CMD_STOP: &'static str = "stop";
+pub const CMD_STOP_ABOUT: &'static str = "Stop the current work session";
+
+pub const ARG_ROUNDING: &'static str = "CASS_ROUNDING";
+pub const ARG_ROUNDING_ABOUT: &'static str = "Disable the (default) 15 minute rounding period";
+
+pub const CMD_INVOICE: &'static str = "invoice";
+pub const CMD_INVOICE_ABOUT: &'static str = "Create an invoice.  You get to choose between simply adding a \
+statement to your time file, or generating .yml configuration to build an invoice generator from.  See invoice(1) \
+for more detail!";
+
+pub const CMD_UPDATE: &'static str = "update";
+pub const CMD_UPDATE_ABOUT: &'static str = "Update the selected file to a new version";
+
+pub const ARG_CLIENT: &'static str = "CLIENT";
+pub const ARG_CLIENT_ABOUT: &'static str =
+    "Provide the name of the current client for invoice generation";
+
+pub const ARG_PROJECT: &'static str = "PROJECT";
+pub const ARG_PROJECT_ABOUT: &'static str =
+    "Provide the name of the current project for invoice generation";
+
+pub const ARG_GEN_YAML: &'static str = "GEN_YAML";
+pub const ARG_GEN_YAML_ABOUT: &'static str =
+    "Specify whether to generate a .yml invoice configuration";
+
+pub const ARG_CLIENT_DB: &'static str = "CLIENT_DB";
+pub const ARG_CLIENT_DB_ABOUT: &'static str =
+    "Provide your client database file (.yml format) used by invoice(1)";
+
+pub const CMD_STAT: &'static str = "stat";
+pub const CMD_STAT_ABOUT: &'static str = "Get statistics of previous work sessions";
diff --git a/apps/koffice/libko/src/cass/mod.rs b/apps/koffice/libko/src/cass/mod.rs
new file mode 100644
index 000000000000..43dd79b0fbd7
--- /dev/null
+++ b/apps/koffice/libko/src/cass/mod.rs
@@ -0,0 +1,160 @@
+//! Cassiopeia plain text time tracking tool
+//!
+//! Versions `0.1` and `0.2` were written in Ruby and are thus
+//! deprecated.  Most likely you are interested in `cass(1)`, the
+//! simple plain text time tracking utility, part of the kookie-office
+//! suite of commandline tools!  This is the library powering it.
+//!
+//! For more documentation, check out:
+//! https://git.spacekookie.de/kookienomicon/tree/apps/cassiopeia
+
+mod data;
+mod date;
+mod format;
+mod time;
+mod timeline;
+
+pub mod error;
+pub mod meta;
+
+pub use date::Date;
+pub use time::Time;
+
+pub(crate) use data::TimeFile;
+use data::{Invoice, Session};
+use error::{ParseError, ParseResult};
+use format::{
+    ir::{append_ir, clean_ir, IrStream, MakeIr},
+    ParseOutput,
+};
+
+/// A state handler and primary API for all cass interactions
+///
+///
+pub struct Cassiopeia {
+    path: String,
+    tf: TimeFile,
+    ir: IrStream,
+}
+
+impl Cassiopeia {
+    /// Load a cass file from disk, parsing it into a [`TimeFile`](crate::TimeFile)
+    pub fn load(path: &str) -> ParseResult<Self> {
+        let path = path.to_owned();
+        format::load_file(path.as_str()).map(|ParseOutput { tf, ir }| Self { path, tf, ir })
+    }
+
+    pub(crate) fn timefile(&self) -> TimeFile {
+        self.tf.clone()
+    }
+
+    /// Start a new work session (with optional 15 minute rounding)
+    pub fn start(&mut self, round: bool) -> ParseResult<()> {
+        let delta = self.tf.timeline.start(Time::rounded(round))?;
+        clean_ir(&mut self.ir);
+        append_ir(&mut self.ir, delta.make_ir());
+        format::write_file(self.path.as_str(), &mut self.ir)
+    }
+
+    /// Stop the existing work session (with optional 15 minute rounding)
+    pub fn stop(&mut self, round: bool) -> ParseResult<()> {
+        let delta = self.tf.timeline.stop(Time::rounded(round))?;
+        clean_ir(&mut self.ir);
+        append_ir(&mut self.ir, delta.make_ir());
+        format::write_file(self.path.as_str(), &mut self.ir)
+    }
+
+    /// Add an invoice block to the time file
+    pub fn invoice<'slf>(&'slf mut self) -> Invoicer<'slf> {
+        Invoicer::new(self)
+    }
+
+    /// Write out the file IR as is, updating only the header version
+    pub fn update(&mut self) -> ParseResult<()> {
+        clean_ir(&mut self.ir);
+        format::write_file(self.path.as_str(), &mut self.ir)
+    }
+
+    /// Collect statistics on previous work sessions
+    pub fn stat(&self) -> ParseResult<String> {
+        todo!()
+    }
+}
+
+/// An invoice generator builder
+///
+/// The most simple use-case of this type is to provide no parameters
+/// and simply add an `INVOICE` line to the cass file.  Adittionally
+/// you may provide the client and project name, which will then
+/// require the `client_db` path to be set as well.
+///
+/// ```rust,no_run
+/// # let mut cass = cassiopeia::Cassiopeia::load("").unwrap();
+/// cass.invoice().run();
+/// ```
+///
+/// Additional errors can be thrown if the client or project are not
+/// known in the client db.
+///
+/// ```rust,no_run
+/// # let mut cass = cassiopeia::Cassiopeia::load("").unwrap();
+/// cass.invoice()
+///     .generate()
+///     .db("/home/office/clients.yml".into())
+///     .client("ACME".into())
+///     .run();
+/// ```
+#[allow(unused)]
+pub struct Invoicer<'cass> {
+    tf: &'cass mut Cassiopeia,
+    generate: bool,
+    client_db: String,
+    client: String,
+    project: String,
+}
+
+impl<'cass> Invoicer<'cass> {
+    pub fn new(tf: &'cass mut Cassiopeia) -> Self {
+        Self {
+            tf,
+            generate: false,
+            client_db: String::new(),
+            client: String::new(),
+            project: String::new(),
+        }
+    }
+
+    /// Enable the invoice generation feature
+    pub fn generate(self) -> Self {
+        Self {
+            generate: true,
+            ..self
+        }
+    }
+
+    /// Provide the client database file (.yml format)
+    pub fn db(self, client_db: String) -> Self {
+        Self { client_db, ..self }
+    }
+
+    /// Provide the client to invoice
+    pub fn client(self, client: String) -> Self {
+        Self { client, ..self }
+    }
+
+    pub fn project(self, project: String) -> Self {
+        Self { project, ..self }
+    }
+
+    pub fn run(mut self) -> ParseResult<()> {
+        if self.generate {
+            eprintln!("Integration with invoice(1) is currently not implemented.  Sorry :(");
+            return Err(ParseError::Unknown);
+        }
+
+        let delta = self.tf.tf.timeline.invoice(Date::today())?;
+        clean_ir(&mut self.tf.ir);
+        append_ir(&mut self.tf.ir, delta.make_ir());
+        format::write_file(self.tf.path.as_str(), &mut self.tf.ir)
+    }
+}
diff --git a/apps/koffice/libko/src/cass/time.rs b/apps/koffice/libko/src/cass/time.rs
new file mode 100644
index 000000000000..48d4d5f9be2e
--- /dev/null
+++ b/apps/koffice/libko/src/cass/time.rs
@@ -0,0 +1,141 @@
+use crate::cass::Date;
+use chrono::{
+    DateTime, Duration, FixedOffset as Offset, Local, NaiveDateTime, NaiveTime, TimeZone, Timelike,
+    Utc,
+};
+use std::{cmp::Ordering, ops::Sub};
+
+/// A convenience wrapper around [DateTime][t] with fixed timezone
+///
+/// [t]: chrono::DateTime
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Time {
+    inner: DateTime<Offset>,
+}
+
+impl From<DateTime<Offset>> for Time {
+    fn from(inner: DateTime<Offset>) -> Self {
+        Self { inner }
+    }
+}
+
+impl<'t> Sub for &'t Time {
+    type Output = Duration;
+
+    fn sub(self, o: &'t Time) -> Self::Output {
+        self.inner - o.inner
+    }
+}
+
+impl ToString for Time {
+    fn to_string(&self) -> String {
+        format!("{}", self.inner.format("%Y-%m-%d %H:%M:%S%:z"))
+    }
+}
+
+impl Time {
+    /// Get the current local time and pin it to a fixed Tz offset
+    pub fn now() -> Self {
+        let now = Local::now();
+        Self {
+            inner: build_datetime(
+                now.time()
+                    .with_second(0)
+                    .and_then(|t| t.with_nanosecond(0))
+                    .unwrap(),
+            ),
+        }
+    }
+
+    /// Get the time that might be rounded to the next 15 minutes
+    pub(crate) fn rounded(r: bool) -> Self {
+        if r {
+            Time::now().round()
+        } else {
+            Time::now()
+        }
+    }
+
+    pub(crate) fn date(&self) -> chrono::Date<Offset> {
+        self.inner.date()
+    }
+
+    /// Check if a time stamp happened _after_ a date
+    pub fn after(&self, date: &Date) -> bool {
+        &Date::from(self.date()) > date
+    }
+
+    #[cfg(test)]
+    pub(crate) fn fixed(hour: u32, min: u32, sec: u32) -> Self {
+        Self {
+            inner: build_datetime(NaiveTime::from_hms(hour, min, sec)),
+        }
+    }
+
+    /// Return a new instance that is rounded to nearest 15 minutes
+    ///
+    /// It uses the internally provided offset to do rounding, meaning
+    /// that the timezone information will not change, even when
+    /// rounding values that were created in a different timezone.
+    pub fn round(&self) -> Self {
+        let naive = self.inner.time();
+        let (new_min, incr_hour) = match naive.minute() {
+            // 0-7 => (0, false)
+            m if m < 7 => (0, false),
+            // 7-22 => (15, false)
+            m if m >= 7 && m < 22 => (15, false),
+            // 22-37 => (30, false)
+            m if m >= 22 && m < 37 => (30, false),
+            // 37-52 => (45, false)
+            m if m >= 37 && m < 52 => (45, false),
+            // 52-59 => (0, true)
+            m if m >= 52 && m <= 59 => (0, true),
+            _ => unreachable!(),
+        };
+
+        let hour = naive.hour();
+        let new = NaiveTime::from_hms(if incr_hour { hour + 1 } else { hour }, new_min, 0);
+        let offset = self.inner.offset();
+        let date = self.inner.date();
+
+        Self {
+            inner: DateTime::from_utc(NaiveDateTime::new(date.naive_local(), new), *offset),
+        }
+    }
+
+    pub fn hour(&self) -> u32 {
+        self.inner.hour()
+    }
+
+    pub fn minute(&self) -> u32 {
+        self.inner.minute()
+    }
+
+    pub fn second(&self) -> u32 {
+        self.inner.second()
+    }
+}
+
+/// Build a DateTime with the current local fixed offset
+fn build_datetime(nt: NaiveTime) -> DateTime<Offset> {
+    let date = Utc::now().date().naive_local();
+    let offset = Local.offset_from_utc_date(&date);
+
+    DateTime::from_utc(NaiveDateTime::new(date, nt), offset)
+}
+
+#[test]
+fn simple() {
+    let t = Time::fixed(10, 44, 0);
+    let round = t.round();
+    assert_eq!(round.minute(), 45);
+
+    let t = Time::fixed(6, 8, 0);
+    let round = t.round();
+    assert_eq!(round.minute(), 15);
+
+    let t = Time::fixed(6, 55, 0);
+    let round = t.round();
+    assert_eq!(round.minute(), 0);
+    assert_eq!(round.hour(), 7);
+}
diff --git a/apps/koffice/libko/src/cass/timeline.rs b/apps/koffice/libko/src/cass/timeline.rs
new file mode 100644
index 000000000000..057f0b47d7da
--- /dev/null
+++ b/apps/koffice/libko/src/cass/timeline.rs
@@ -0,0 +1,132 @@
+use crate::cass::{
+    data::{Delta, Invoice, Session},
+    error::{UserError, UserResult},
+    Date, Time,
+};
+
+/// A timeline entry of sessions and invoices
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub enum Entry {
+    Session(Session),
+    Invoice(Invoice),
+}
+
+impl From<Session> for Entry {
+    fn from(s: Session) -> Self {
+        Self::Session(s)
+    }
+}
+
+impl From<Invoice> for Entry {
+    fn from(i: Invoice) -> Self {
+        Self::Invoice(i)
+    }
+}
+
+/// A timeline of sessions and invoices, ordered chronologically
+#[derive(Debug, Default, Clone)]
+pub struct Timeline {
+    inner: Vec<Entry>,
+}
+
+impl Timeline {
+    /// Take a set of sessions and invoices to sort into a timeline
+    pub fn build(s: Vec<Session>, i: Vec<Invoice>) -> Self {
+        let mut inner: Vec<_> = s.into_iter().map(|s| Entry::Session(s)).collect();
+        inner.append(&mut i.into_iter().map(|i| Entry::Invoice(i)).collect());
+        Self { inner }
+    }
+
+    /// Utility function to get the last session in the timeline
+    fn last_session(&mut self) -> Option<&mut Session> {
+        self.inner
+            .iter_mut()
+            .find(|e| match e {
+                Entry::Session(_) => true,
+                _ => false,
+            })
+            .map(|e| match e {
+                Entry::Session(ref mut s) => s,
+                _ => unreachable!(),
+            })
+    }
+
+    /// Utility function to get the last invoice in the timeline
+    fn last_invoice(&self) -> Option<&Invoice> {
+        self.inner
+            .iter()
+            .find(|e| match e {
+                Entry::Invoice(_) => true,
+                _ => false,
+            })
+            .map(|e| match e {
+                Entry::Invoice(ref s) => s,
+                _ => unreachable!(),
+            })
+    }
+
+    /// Get a list of sessions that happened up to a certain invoice date
+    ///
+    /// **WARNING** If there is no invoice with the given date, this
+    /// function will return garbage data, so don't call it with
+    /// invoice dates that don't exist.
+    ///
+    /// Because: if the date passes other invoices on the way, the accumulator
+    /// will be discarded and a new count will be started.
+    pub fn session_iter(&self, date: &Date) -> Vec<&Session> {
+        self.inner
+            .iter()
+            .fold((false, vec![]), |(mut done, mut acc), entry| {
+                match (done, entry) {
+                    // Put sessions into the accumulator
+                    (false, Entry::Session(ref s)) => acc.push(s),
+                    // When we reach the target invoice, terminate the iterator
+                    (false, Entry::Invoice(ref i)) if &i.date == date => done = true,
+                    // When we hit another invoice, empty accumulator
+                    (false, Entry::Invoice(_)) => acc.clear(),
+                    // When we are ever "done", skip all other entries
+                    (true, _) => {}
+                }
+
+                (done, acc)
+            })
+            .1
+    }
+
+    /// Start a new session, if no active session is already in progress
+    pub fn start(&mut self, time: Time) -> UserResult<Delta> {
+        match self.last_session() {
+            Some(s) if !s.finished() => Err(UserError::ActiveSessionExists),
+            _ => Ok(()),
+        }?;
+
+        self.inner.push(Session::start(time.clone()).into());
+        Ok(Delta::Start(time))
+    }
+
+    /// Stop an ongoing session, if one exists
+    pub fn stop(&mut self, time: Time) -> UserResult<Delta> {
+        match self.last_session() {
+            Some(s) if s.finished() => Err(UserError::NoActiveSession),
+            _ => Ok(()),
+        }?;
+
+        self.last_session().unwrap().stop(time.clone());
+        Ok(Delta::Stop(time))
+    }
+
+    /// Create a new invoice on the given day
+    pub fn invoice(&mut self, date: Date) -> UserResult<Delta> {
+        match self.last_invoice() {
+            // If an invoice on the same day exists already
+            Some(i) if i.date == date => Err(UserError::SameDayInvoice),
+            // If there was no work since the last invoice
+            Some(ref i) if self.session_iter(&i.date).len() == 0 => Err(UserError::NoWorkInvoice),
+            // Otherwise everything is coolio
+            _ => Ok(()),
+        }?;
+
+        self.inner.push(Invoice::new(date.clone()).into());
+        Ok(Delta::Invoice(date))
+    }
+}
diff --git a/apps/koffice/libko/src/client.rs b/apps/koffice/libko/src/client.rs
new file mode 100644
index 000000000000..8e256160d3d3
--- /dev/null
+++ b/apps/koffice/libko/src/client.rs
@@ -0,0 +1,39 @@
+use chrono::NaiveDate;
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct Worker {
+    pub name: String,
+    pub address: Address,
+    pub account: Account,
+}
+
+/// An entry in the client database
+#[derive(Debug, Serialize, Deserialize)]
+pub struct Client {
+    pub name: String,
+    pub address: Address,
+    pub last_project: Option<NaiveDate>,
+}
+
+/// An address with all associated data
+#[derive(Debug, Serialize, Deserialize)]
+pub struct Address {
+    pub name: String,
+    pub street: String,
+    pub no: String,
+    pub zip: String,
+    pub city: String,
+    pub country: String,
+}
+
+/// A bank account with a account, and bank number
+///
+/// This is kept as generically as possible, to allow as many
+/// different account representations to work.
+#[derive(Debug, Serialize, Deserialize)]
+pub struct Account {
+    pub bank_name: String,
+    pub acc_num: String,
+    pub bank_num: String,
+}
diff --git a/apps/koffice/libko/src/config.rs b/apps/koffice/libko/src/config.rs
new file mode 100644
index 000000000000..bef9c6fd2377
--- /dev/null
+++ b/apps/koffice/libko/src/config.rs
@@ -0,0 +1,5 @@
+use std::path::PathBuf;
+
+pub struct AppSettings {
+    
+}
diff --git a/apps/koffice/libko/src/invoice.rs b/apps/koffice/libko/src/invoice.rs
new file mode 100644
index 000000000000..737513785916
--- /dev/null
+++ b/apps/koffice/libko/src/invoice.rs
@@ -0,0 +1,35 @@
+use chrono::NaiveDate;
+use serde::{Deserialize, Serialize};
+use std::string::ToString;
+
+/// A specification to build invoice IDs with
+#[derive(Serialize, Deserialize)]
+pub enum InvoiceId {
+    YearMonthId(u16, u8, usize),
+}
+
+impl ToString for InvoiceId {
+    fn to_string(&self) -> String {
+        match self {
+            Self::YearMonthId(yr, mo, id) => format!("#{}-{:02}-{:04}", yr, mo, id),
+        }
+    }
+}
+
+/// An invoice for a specific project
+#[derive(Serialize, Deserialize)]
+pub struct Invoice {
+    id: InvoiceId,
+    client: String,
+    project: String,
+    date: NaiveDate,
+    amount: usize,
+    currency: String,
+    vat: u8,
+}
+
+#[test]
+fn invoice_id_fmt() {
+    let inv_id = InvoiceId::YearMonthId(2020, 06, 0055);
+    assert_eq!(inv_id.to_string(), "#2020-06-0055".to_string());
+}
diff --git a/apps/koffice/libko/src/lib.rs b/apps/koffice/libko/src/lib.rs
new file mode 100644
index 000000000000..33d6b38ae1b1
--- /dev/null
+++ b/apps/koffice/libko/src/lib.rs
@@ -0,0 +1,35 @@
+//! A library that provides basic building blocks of k-office tools
+
+pub mod cass;
+
+mod client;
+pub use client::*;
+
+mod invoice;
+pub use invoice::*;
+
+mod proj;
+pub use proj::*;
+
+mod store;
+pub use store::*;
+
+use serde::{de::DeserializeOwned, Serialize};
+
+pub trait Io {
+    fn to_yaml(&self) -> String;
+    fn from_yaml(s: impl Into<String>) -> Self;
+}
+
+impl<T> Io for T
+where
+    T: Serialize + DeserializeOwned,
+{
+    fn to_yaml(&self) -> String {
+        serde_yaml::to_string(self).unwrap()
+    }
+
+    fn from_yaml(s: impl Into<String>) -> Self {
+        serde_yaml::from_str(s.into().as_str()).unwrap()
+    }
+}
diff --git a/apps/koffice/libko/src/proj.rs b/apps/koffice/libko/src/proj.rs
new file mode 100644
index 000000000000..1e370fc2aaaf
--- /dev/null
+++ b/apps/koffice/libko/src/proj.rs
@@ -0,0 +1,15 @@
+use chrono::NaiveDate;
+use serde::{Deserialize, Serialize};
+
+/// Represent a project that is being done
+#[derive(Serialize, Deserialize)]
+pub struct Project {
+    client: String,
+    date: NaiveDate,
+}
+
+impl Project {
+    pub fn new(client: String, date: NaiveDate) -> Self {
+        Self { client, date }
+    }
+}
diff --git a/apps/koffice/libko/src/store.rs b/apps/koffice/libko/src/store.rs
new file mode 100644
index 000000000000..7ce33ce5fd51
--- /dev/null
+++ b/apps/koffice/libko/src/store.rs
@@ -0,0 +1,94 @@
+use crate::{
+    cass::{Cassiopeia, TimeFile},
+    Address, Client, Io,
+};
+use serde::{Deserialize, Serialize};
+use std::collections::BTreeMap;
+use std::{
+    fs::File,
+    io::{Read, Write},
+    path::PathBuf,
+};
+use xdg::BaseDirectories as BaseDirs;
+
+#[derive(Debug)]
+pub struct Meta {
+    clients: BTreeMap<String, Client>,
+    pub dir: BaseDirs,
+    pub invoice_dir: PathBuf,
+    pub template: Option<PathBuf>,
+    pub revisioning: bool,
+
+    /// Optional current timefile path
+    pub timefile: Option<TimeFile>,
+    pub project_id: Option<String>,
+}
+
+///
+#[derive(Debug, Serialize, Deserialize)]
+pub struct Config {
+    pub revisioning: bool,
+    pub invoice_dir: PathBuf,
+}
+
+impl Meta {
+    pub fn new(dir: BaseDirs) -> Self {
+        // Get the path to the configuration, and make sure a default
+        // configuration is created if none exists yet.
+        let path = dir.find_config_file("config.yml").unwrap_or_else(|| {
+            let path = dir.place_config_file("config.yml").unwrap();
+            let mut cfg = File::create(path.clone()).unwrap();
+
+            let buf = "revisioning: true
+invoicedir: $HOME/.local/k-office/";
+            cfg.write_all(buf.as_bytes()).unwrap();
+            path
+        });
+
+        let mut cfg = File::open(path).unwrap();
+
+        let mut buf = String::new();
+        cfg.read_to_string(&mut buf).unwrap();
+        let yml = Config::from_yaml(buf);
+
+        Self {
+            dir,
+            clients: BTreeMap::new(),
+            invoice_dir: yml.invoice_dir,
+            template: None,
+            revisioning: yml.revisioning,
+            timefile: None,
+            project_id: None,
+        }
+    }
+
+    pub fn load_timefile(&mut self, path: &str) {
+        let timefile = Cassiopeia::load(path)
+            .expect("Timefile not found")
+            .timefile();
+        self.timefile = Some(timefile);
+    }
+
+    pub fn client_mut(&mut self, name: &str) -> Option<&mut Client> {
+        self.clients.get_mut(name)
+    }
+
+    pub fn new_client(&mut self, name: &str, address: Address) {
+        self.clients.insert(
+            name.to_string(),
+            Client {
+                name: name.to_string(),
+                address,
+                last_project: None,
+            },
+        );
+    }
+}
+
+/// Initialise a k-office application state
+pub fn initialise() -> Meta {
+    let dir = BaseDirs::with_prefix("k-koffice").unwrap();
+    dir.create_config_directory("")
+        .expect("Couldn't create config directory");
+    Meta::new(dir)
+}
diff --git a/apps/koffice/libko/src/timefile.rs b/apps/koffice/libko/src/timefile.rs
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/apps/koffice/libko/src/timefile.rs