tix-tracker 0.12.0

//! The `[kanban.<name>.wip]` schema: per-column limits, estimate units, and the
//! arithmetic between them (mission `configurable-wip-limits-01M3C6WX`, WP01).
//!
//! # The shape, and why it looks like this
//!
//! ```toml
//! [kanban.default.wip.units]
//! d = 1      # a `d` is one base point
//! w = 5      # a `w` is five
//!
//! [kanban.default.wip.limits."in progress"]
//! max_items = 3
//! max_estimate = 10
//! unit = "d"       # what `max_estimate` counts in
//! policy = "block" # `warn` or `block` — required, never assumed
//! enabled = true   # default; `false` keeps the numbers but enforces nothing
//! ```
//!
//! Three decisions are worth stating, because each one is a door that stays shut:
//!
//! 1. **The column is the key.** A limit cannot name a column that does not exist
//!    and cannot be declared twice; validation then checks the key against the
//!    board's own [`columns`](crate::config::BoardConfiguration::columns).
//! 2. **`policy` is required, not defaulted.** "Warning or blocking behaviour by
//!    configuration" (C-004) is only true if the choice is written down; a limit
//!    that silently warned would be a policy nobody configured. The field is
//!    `Option<LimitPolicy>` so "absent" is distinguishable from "warn" and can be
//!    refused by name.
//! 3. **Units are declarative and the arithmetic is exact.** A board declares named
//!    units and their factor to its base unit; an issue's free-form `estimate`
//!    (`3d`, or a bare `3` which is already in the limit's unit) is converted by
//!    `value × factor(from) ÷ factor(to)`. A unit the board never declared is a
//!    `missing_conversion`, and a conversion that does not divide exactly is an
//!    `ambiguous_conversion` — never a rounded or defaulted count (C-003).
//!
//!    The text may also be a **human duration**: `1 day`, `2 days`,
//!    `3 weeks 2 hours`, `2w`, `1d 30 min` (tix #1724). Each term is converted
//!    through the board's own units and the converted terms are summed, so a
//!    prose estimate never invents a clock ratio the board did not declare:
//!    `3 weeks 2 hours` on a board with `w = 5` and `h = 1` is `17`, not
//!    `506` (C-003 still holds).
//!
//! # What this module does not own
//!
//! The status categories and the completion semantics stay
//! [`crate::workflow`]'s (C-002): nothing here reads a category, decides what
//! "done" means, or interprets `done_column`. Counting issues, deciding a move, and
//! writing an override are the later work packages; this one owns what a limit *is*.

use indexmap::IndexMap;
use serde::{Deserialize, Serialize};

use crate::error::TixError;

/// Whether a limit warns or blocks (C-004).
///
/// There is no third behaviour and no "silent": a limit that is not enforced is
/// [`enabled = false`](ColumnLimit::enabled), which is a different statement from
/// "warn" and reads as one.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
pub enum LimitPolicy {
    /// The move proceeds and the violation is reported.
    Warn,
    /// The move is refused unless an authorized override carries it.
    Block,
}

impl LimitPolicy {
    /// The stable spelling every surface prints and `tix.toml` stores.
    pub const fn as_str(self) -> &'static str {
        match self {
            Self::Warn => "warn",
            Self::Block => "block",
        }
    }
}

/// The `enabled` default: declaring a limit means applying it.
const fn enabled_default() -> bool {
    true
}

/// `serde`'s `skip_serializing_if` takes a `&T` predicate, so the reference is the
/// signature the attribute needs rather than a choice.
#[allow(clippy::trivially_copy_pass_by_ref)]
fn is_enabled_default(enabled: &bool) -> bool {
    *enabled
}

/// One column's limit.
///
/// Both ceilings are optional and independent: a column may cap the *number* of
/// cards, the *estimate* they add up to, or both. An enabled limit with neither is
/// refused, because a limit that limits nothing is a configuration mistake that
/// would otherwise read as an enforced rule.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
#[serde(default, deny_unknown_fields)]
pub struct ColumnLimit {
    /// The most cards the column may hold.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub max_items: Option<u32>,
    /// The most estimate the column's cards may add up to, counted in [`unit`].
    ///
    /// [`unit`]: ColumnLimit::unit
    #[serde(skip_serializing_if = "Option::is_none")]
    pub max_estimate: Option<u32>,
    /// The unit `max_estimate` counts in. Required with `max_estimate`, refused
    /// without it: a unit on an item-count limit would describe nothing.
    #[serde(skip_serializing_if = "Option::is_none")]
    pub unit: Option<String>,
    /// `warn` or `block`. Required for an enabled limit (see the module docs).
    #[serde(skip_serializing_if = "Option::is_none")]
    pub policy: Option<LimitPolicy>,
    /// Whether the limit is enforced. `false` keeps the numbers for later without
    /// changing any behaviour today.
    #[serde(
        default = "enabled_default",
        skip_serializing_if = "is_enabled_default"
    )]
    pub enabled: bool,
}

impl Default for ColumnLimit {
    fn default() -> Self {
        Self {
            max_items: None,
            max_estimate: None,
            unit: None,
            policy: None,
            enabled: true,
        }
    }
}

impl ColumnLimit {
    /// A limit capping the column at `max_items` cards, with `policy`.
    pub fn items(max_items: u32, policy: LimitPolicy) -> Self {
        Self {
            max_items: Some(max_items),
            policy: Some(policy),
            ..Self::default()
        }
    }

    /// A limit capping the column at `max_estimate` `unit`s, with `policy`.
    pub fn estimate(max_estimate: u32, unit: impl Into<String>, policy: LimitPolicy) -> Self {
        Self {
            max_estimate: Some(max_estimate),
            unit: Some(unit.into()),
            policy: Some(policy),
            ..Self::default()
        }
    }

    /// Whether nothing at all is declared: the state the schema omits on save.
    pub fn is_empty(&self) -> bool {
        self.max_items.is_none()
            && self.max_estimate.is_none()
            && self.unit.is_none()
            && self.policy.is_none()
            && self.enabled == enabled_default()
    }

    /// The policy this limit enforces, when it is enforced at all.
    ///
    /// `None` for a disabled limit *and* for an enabled one that forgot to state a
    /// policy — validation refuses the latter, so a caller that has validated a
    /// config and asked an **enabled** limit for its policy always gets one.
    pub fn resolved_policy(&self) -> Option<LimitPolicy> {
        self.enabled.then_some(self.policy).flatten()
    }
}

/// A board's work-in-progress configuration (`[kanban.<name>.wip]`).
///
/// Omitted **whole** when nothing is declared (`limits` and `units` both empty), so
/// a board that configures no limits gains no key on save — the same rule every
/// other board field follows (#1415).
#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize)]
#[serde(default, deny_unknown_fields)]
pub struct WipConfig {
    /// Named estimate units, `name -> factor` to the board's base unit, in
    /// declaration order.
    #[serde(skip_serializing_if = "IndexMap::is_empty")]
    pub units: IndexMap<String, u32>,
    /// `<column> -> limit`, in declaration order.
    #[serde(skip_serializing_if = "IndexMap::is_empty")]
    pub limits: IndexMap<String, ColumnLimit>,
}

impl WipConfig {
    /// The limits, in declaration order.
    pub fn limits(&self) -> impl Iterator<Item = (&str, &ColumnLimit)> {
        self.limits
            .iter()
            .map(|(column, limit)| (column.as_str(), limit))
    }

    /// Whether no limit and no unit is declared: the state that writes nothing.
    pub fn is_empty(&self) -> bool {
        self.units.is_empty() && self.limits.is_empty()
    }

    /// Whether any limit is actually enforced.
    pub fn has_enabled_limits(&self) -> bool {
        self.limits.values().any(|limit| limit.enabled)
    }

    /// The limit **in force** for `column`, if any (T004).
    ///
    /// This is the resolver every surface asks — not the raw map — so "declared but
    /// disabled" cannot be mistaken for "enforced" by one caller and not another.
    /// It decides nothing else: what a violation *means* is the policy layer's, and
    /// what a column *is* stays [`crate::workflow`]'s (C-002).
    pub fn effective_limit(&self, column: &str) -> Option<&ColumnLimit> {
        self.limits
            .get(column)
            .filter(|limit| limit.enabled && !limit.is_empty())
    }

    /// The conversion factor of `unit`, if the board declares it.
    pub fn factor(&self, unit: &str) -> Option<u32> {
        self.units.get(unit).copied()
    }

    /// Convert `estimate` into `target`, using the declared factors (T002).
    ///
    /// A bare estimate is **already** in `target` — the limit names the unit, so
    /// there is nothing to infer. A named one must be declared by the board, and the
    /// arithmetic must divide exactly: a fractional result is refused rather than
    /// rounded, because a count that depends on rounding is a count nobody can
    /// predict.
    pub fn convert(&self, estimate: &Estimate, target: &str) -> std::result::Result<u32, WipError> {
        let target_factor = self.factor(target).ok_or_else(|| {
            WipError::single(WipDiagnostic::new(
                WipDiagnosticKind::UnknownUnit,
                format!("`{target}` is not a declared estimate unit"),
            ))
            .because("declare the unit under `[kanban.<board>.wip.units]`")
        })?;
        let Some(unit) = estimate.unit.as_deref() else {
            // The same unit: nothing to convert, and nothing assumed.
            return Ok(estimate.value);
        };
        if unit == target {
            return Ok(estimate.value);
        }
        let from_factor = self.factor(unit).ok_or_else(|| {
            WipError::single(WipDiagnostic::new(
                WipDiagnosticKind::MissingConversion,
                format!(
                    "`{}` uses estimate unit `{unit}`, which this board does not declare",
                    estimate.render()
                ),
            ))
            .because("a missing conversion is an error, never a zero or a guess (C-003)")
        })?;
        let scaled = (estimate.value as u64) * (from_factor as u64);
        let target_factor = target_factor as u64;
        if scaled % target_factor != 0 {
            return Err(WipError::single(WipDiagnostic::new(
                WipDiagnosticKind::AmbiguousConversion,
                format!(
                    "`{}` is {scaled} base points, which is not a whole number of `{target}` \
                     (a `{target}` is {target_factor})",
                    estimate.render()
                ),
            ))
            .because(
                "declare a unit the arithmetic divides evenly into, or rewrite the estimate",
            ));
        }
        Ok((scaled / target_factor) as u32)
    }

    /// Convert every term of a parsed estimate and sum them (tix #1724).
    ///
    /// This is the only way a compound duration becomes one number. Each term keeps
    /// its own declared unit, so `3 weeks 2 hours` is `3 × w + 2 × h` in the target
    /// — never a clock-ratio guess. One unconvertible term refuses the whole sum and
    /// names itself, because a partial total would silently undercount.
    pub fn convert_terms(
        &self,
        estimates: &[Estimate],
        target: &str,
    ) -> std::result::Result<u32, WipError> {
        if estimates.is_empty() {
            return Err(Estimate::malformed(
                "an estimate must state at least one term".to_string(),
            ));
        }
        let mut total: u64 = 0;
        for estimate in estimates {
            total += u64::from(self.convert(estimate, target)?);
            if total > u64::from(u32::MAX) {
                return Err(Estimate::malformed(format!(
                    "the estimate terms sum past what this board can count in `{target}`"
                )));
            }
        }
        Ok(total as u32)
    }

    /// Validate the schema against the board it belongs to (T001, T003).
    ///
    /// Every finding is a `tix.toml` error naming the exact key, in the same shape
    /// the neighbouring board checks use. A **disabled** limit is still validated:
    /// it is configuration either way, and a limit aimed at a column that does not
    /// exist is a mistake whether or not it is switched on.
    pub fn validate(&self, board: &str, columns: &[String]) -> std::result::Result<(), TixError> {
        for (name, factor) in &self.units {
            if name.trim().is_empty() {
                return Err(TixError::Config(format!(
                    "`kanban.{board}.wip.units` must not contain a blank unit name"
                )));
            }
            if *factor == 0 {
                return Err(TixError::Config(format!(
                    "`kanban.{board}.wip.units.{name}` must be at least 1"
                )));
            }
        }
        for (column, limit) in &self.limits {
            let key = format!("kanban.{board}.wip.limits.`{column}`");
            if !columns.contains(column) {
                return Err(TixError::Config(format!(
                    "`{key}` names a column that is not in `kanban.{board}.columns`"
                )));
            }
            if limit.max_items == Some(0) {
                return Err(TixError::Config(format!(
                    "`{key}.max_items` must be at least 1"
                )));
            }
            if limit.max_estimate == Some(0) {
                return Err(TixError::Config(format!(
                    "`{key}.max_estimate` must be at least 1"
                )));
            }
            if let Some(unit) = &limit.unit
                && !self.units.contains_key(unit)
            {
                return Err(TixError::Config(format!(
                    "`{key}.unit` (`{unit}`) is not declared in \
                     `kanban.{board}.wip.units`"
                )));
            }
            if limit.max_estimate.is_some() && limit.unit.is_none() {
                return Err(TixError::Config(format!(
                    "`{key}.unit` is required with `max_estimate`: it says what the \
                     ceiling counts"
                )));
            }
            if limit.max_estimate.is_none() && limit.unit.is_some() {
                return Err(TixError::Config(format!(
                    "`{key}.unit` is only meaningful with `max_estimate`"
                )));
            }
            if limit.enabled {
                if limit.max_items.is_none() && limit.max_estimate.is_none() {
                    return Err(TixError::Config(format!(
                        "`{key}` is enabled but declares neither `max_items` nor \
                         `max_estimate`"
                    )));
                }
                if limit.policy.is_none() {
                    return Err(TixError::Config(format!(
                        "`{key}.policy` is required: say whether the limit `warn`s or \
                         `block`s (C-004)"
                    )));
                }
            }
        }
        Ok(())
    }
}

/// An estimate as an issue writes it: a number, and optionally the unit it is in.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct Estimate {
    /// The number the issue states.
    pub value: u32,
    /// The unit it is stated in, or `None` when it is already in the limit's unit.
    pub unit: Option<String>,
}

impl Estimate {
    /// Parse one `<number>[<unit>]` term of the free-form `estimate:` frontmatter.
    ///
    /// A unit starts with an ASCII letter and continues with letters, digits, `_` or
    /// `-`; whitespace between the number and the unit is accepted (`1 day`). Human
    /// duration words are folded to the board's conventional symbols (`day`/`days`
    /// → `d`, `week`/`weeks` → `w`, `hour`/`hours` → `h`, `minute`/`minutes` → `m`,
    /// `second`/`seconds` → `s`); a single-letter unit is left exactly as written, so
    /// a board's own `S` or `p` keeps its meaning. Anything else is refused with the
    /// value quoted back, because an estimate nobody can count is worse than none.
    ///
    /// Use [`Estimate::parse_terms`] for a compound duration (`3 weeks 2 hours`).
    pub fn parse(raw: &str) -> std::result::Result<Self, WipError> {
        let text = raw.trim();
        let mut terms = Self::parse_terms(text)?;
        if terms.len() != 1 {
            return Err(Self::malformed(format!(
                "`{text}` states more than one estimate term"
            )));
        }
        Ok(terms.remove(0))
    }

    /// Parse a free-form estimate into its terms, in the order written (tix #1724).
    ///
    /// Accepted: `<number>` (bare, already in the target unit), `<number><unit>`,
    /// decimal numbers and ranges (`0.5 day`, `0.5-1 day`), and one or more
    /// whitespace/comma-separated terms such as `3 weeks 2 hours`. Each term is read
    /// on its own; nothing is summed here, because the sum is only meaningful after
    /// every term has been converted through the board's declared units
    /// ([`WipConfig::convert_terms`]).
    ///
    /// # Pessimistic ranges and fractions
    ///
    /// A fraction and a range are rounded **up** to a whole number in their own
    /// unit, and a range takes its **upper** bound: `0.5 day` is `1d`, and
    /// `0.5-1 day` is `1d`. That is the pessimistic reading the tracker's limits
    /// and capacity calculations count, and it keeps every value a `u32`.
    ///
    /// # Text around the estimate
    ///
    /// A field that holds several comma-separated annotations keeps the segments
    /// that parse and ignores the ones that do not, so `~300 LOC, 0.5-1 day` reads
    /// as `1d`. If no segment parses, the whole value is malformed. A bare number in
    /// a compound statement is still refused (`3 2h` has no unit for the `3`), as
    /// are `-2`, `twenty`, `3d!` and a number that does not fit a `u32`.
    ///
    /// No duration crate is used here by design: `humantime` and `duration-str`
    /// return a single `Duration`, discarding the per-term units that must each go
    /// through the board's own conversion table. Folding the text to seconds would
    /// also invent the clock ratios C-003 forbids.
    pub fn parse_terms(raw: &str) -> std::result::Result<Vec<Self>, WipError> {
        let text = raw.trim();
        match Self::parse_terms_strict(text) {
            Ok(terms) => Ok(terms),
            Err(whole_error) => {
                // A comma is the one separator that may introduce a non-estimate
                // annotation (`~300 LOC, 0.5-1 day`). Keep every segment that parses
                // on its own and drop the rest; if none parses, the value is
                // malformed as a whole.
                if !text.contains(',') {
                    return Err(whole_error);
                }
                let mut terms = Vec::new();
                for segment in text.split(',') {
                    if let Ok(mut parsed) = Self::parse_terms_strict(segment.trim()) {
                        terms.append(&mut parsed);
                    }
                }
                if terms.is_empty() {
                    return Err(whole_error);
                }
                if terms.len() > 1 && terms.iter().any(|term| term.unit.is_none()) {
                    return Err(Self::malformed(format!(
                        "`{text}` mixes a bare number with unit terms"
                    )));
                }
                Ok(terms)
            }
        }
    }

    /// Parse every term in one annotation. Comma-separated terms are part of the
    /// annotation (`1d, 30 min` is two terms); a comma that introduces words is what
    /// makes the whole annotation fail, and [`parse_terms`](Self::parse_terms) then
    /// falls back to per-segment reading.
    fn parse_terms_strict(text: &str) -> std::result::Result<Vec<Self>, WipError> {
        let mut rest = text;
        let mut terms = Vec::new();
        while !rest.is_empty() {
            rest = rest.trim_start_matches(|c: char| c.is_whitespace() || c == ',');
            if rest.is_empty() {
                break;
            }
            let (term, tail) = Self::parse_term(text, rest)?;
            terms.push(term);
            rest = tail;
        }
        if terms.is_empty() {
            return Err(Self::malformed(format!(
                "`{text}` is not `<number>` or `<number><unit>`"
            )));
        }
        if terms.len() > 1 && terms.iter().any(|term| term.unit.is_none()) {
            return Err(Self::malformed(format!(
                "`{text}` mixes a bare number with unit terms"
            )));
        }
        Ok(terms)
    }

    /// Read one `<number>[-<number>][<unit>]` term and return the untouched tail.
    fn parse_term<'a>(text: &str, rest: &'a str) -> std::result::Result<(Self, &'a str), WipError> {
        let (low, mut tail) = Self::parse_decimal(rest).ok_or_else(|| {
            Self::malformed(format!(
                "`{text}` is not a duration such as `<number><unit>` or `<low>-<high><unit>`"
            ))
        })?;
        tail = tail.trim_start_matches([' ', '\t']);
        let mut high = None;
        if let Some(after_dash) = tail.strip_prefix('-') {
            let after_dash = after_dash.trim_start_matches([' ', '\t']);
            let (value, after_high) = Self::parse_decimal(after_dash).ok_or_else(|| {
                Self::malformed(format!("`{text}` starts a range but has no upper bound"))
            })?;
            high = Some(value);
            tail = after_high.trim_start_matches([' ', '\t']);
        }
        let unit: String = tail
            .chars()
            .take_while(|c| c.is_ascii_alphanumeric() || *c == '_' || *c == '-')
            .collect();
        if unit.is_empty() {
            // A bare term is only meaningful when it ends the annotation; a
            // trailing `.`, `!` or another term is refused by the next iteration
            // (or by the compound check).
            if tail.is_empty() || tail.starts_with(',') {
                let value = Self::pessimistic(low, high, text)?;
                return Ok((Self { value, unit: None }, tail));
            }
            return Err(Self::malformed(format!(
                "`{text}` is not `<number>` or `<number><unit>`"
            )));
        }
        if !is_unit_name(&unit) {
            return Err(Self::malformed(format!(
                "`{text}` has an invalid unit `{unit}`"
            )));
        }
        let value = Self::pessimistic(low, high, text)?;
        Ok((
            Self {
                value,
                unit: Some(canonical_unit_word(&unit)),
            },
            &tail[unit.len()..],
        ))
    }

    /// Read a decimal number and return it with the rest of the string.
    fn parse_decimal(rest: &str) -> Option<(f64, &str)> {
        let bytes = rest.as_bytes();
        let mut end = 0;
        while end < bytes.len() && bytes[end].is_ascii_digit() {
            end += 1;
        }
        if end == 0 {
            return None;
        }
        if end < bytes.len() && bytes[end] == b'.' {
            let fraction_start = end + 1;
            let mut fraction_end = fraction_start;
            while fraction_end < bytes.len() && bytes[fraction_end].is_ascii_digit() {
                fraction_end += 1;
            }
            if fraction_end == fraction_start {
                return None;
            }
            end = fraction_end;
        }
        let value = rest.get(..end)?.parse::<f64>().ok()?;
        value.is_finite().then_some((value, &rest[end..]))
    }

    /// The pessimistic whole number for a value or range: the upper bound, rounded
    /// up. Refuses a number no board can count.
    fn pessimistic(low: f64, high: Option<f64>, text: &str) -> std::result::Result<u32, WipError> {
        let value = high.map_or(low, |upper| low.max(upper)).ceil();
        if value > f64::from(u32::MAX) {
            return Err(Self::malformed(format!(
                "`{text}` is not a number this board can count"
            )));
        }
        Ok(value as u32)
    }

    fn malformed(message: String) -> WipError {
        WipError::single(WipDiagnostic::new(
            WipDiagnosticKind::MalformedEstimate,
            message,
        ))
    }

    /// The estimate as it was written, for a message.
    pub fn render(&self) -> String {
        match &self.unit {
            Some(unit) => format!("{}{unit}", self.value),
            None => self.value.to_string(),
        }
    }
}

/// Fold a human duration word to the symbol a board's unit table uses.
///
/// Only **words** are folded; a one-letter unit is returned verbatim, so `S`, `M`
/// and `L` keep whatever meaning the board gave them.
fn canonical_unit_word(unit: &str) -> String {
    if unit.chars().count() == 1 {
        return unit.to_string();
    }
    match unit.to_ascii_lowercase().as_str() {
        "day" | "days" => "d",
        "week" | "weeks" | "wk" | "wks" => "w",
        "hour" | "hours" | "hr" | "hrs" => "h",
        "minute" | "minutes" | "min" | "mins" => "m",
        "second" | "seconds" | "sec" | "secs" => "s",
        _ => unit,
    }
    .to_string()
}

/// Whether `text` names a unit the schema accepts.
fn is_unit_name(text: &str) -> bool {
    let mut chars = text.chars();
    let Some(first) = chars.next() else {
        return false;
    };
    first.is_ascii_alphabetic() && chars.all(|c| c.is_ascii_alphanumeric() || c == '_' || c == '-')
}

/// What a WIP finding is about (C-003, C-007).
///
/// The kind is the machine-readable half, so `tix lint` and a surface can branch on
/// the condition while the sentence beside it stays a sentence.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub enum WipDiagnosticKind {
    /// An estimate is not `<number>` or `<number><unit>`.
    MalformedEstimate,
    /// An estimate names a unit the board never declared.
    MissingConversion,
    /// A conversion that is not a whole number of the target unit.
    AmbiguousConversion,
    /// A unit reference the board does not declare.
    UnknownUnit,
    /// A declared limit is over its ceiling.
    OverLimit,
    /// A limit violation that an override carried through.
    OverrideApplied,
    /// The blocking limit needs an authorized override to be passed.
    OverrideRequired,
    /// The override was not confirmed explicitly.
    UnconfirmedOverride,
    /// The override is missing the actor, the timestamp or the reason.
    MissingOverrideField,
    /// The override was authorized against a limit that has since changed.
    StaleOverrideLimit,
    /// #183's transition policy refused the move; WIP was never reached.
    RejectedTransition,
}

impl WipDiagnosticKind {
    /// The stable spelling every surface prints.
    pub const fn as_str(self) -> &'static str {
        match self {
            Self::MalformedEstimate => "malformed_estimate",
            Self::MissingConversion => "missing_conversion",
            Self::AmbiguousConversion => "ambiguous_conversion",
            Self::UnknownUnit => "unknown_unit",
            Self::OverLimit => "over_limit",
            Self::OverrideApplied => "override_applied",
            Self::OverrideRequired => "override_required",
            Self::UnconfirmedOverride => "unconfirmed_override",
            Self::MissingOverrideField => "missing_override_field",
            Self::StaleOverrideLimit => "stale_override_limit",
            Self::RejectedTransition => "rejected_transition",
        }
    }
}

/// One WIP finding: what it is, where it is, and what to do about it.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct WipDiagnostic {
    /// What is wrong.
    pub kind: WipDiagnosticKind,
    /// One sentence saying what to do about it.
    pub message: String,
    /// A second sentence, when the first is not enough.
    pub because: Option<String>,
}

impl WipDiagnostic {
    /// A finding with its message.
    pub fn new(kind: WipDiagnosticKind, message: impl Into<String>) -> Self {
        Self {
            kind,
            message: message.into(),
            because: None,
        }
    }

    /// Add the sentence that says what to do about it.
    pub fn because(mut self, because: impl Into<String>) -> Self {
        self.because = Some(because.into());
        self
    }

    /// Render through the crate's one diagnostic renderer.
    pub fn render(&self) -> String {
        let mut pairs = vec![(self.kind.as_str(), self.message.as_str())];
        if let Some(because) = self.because.as_deref() {
            pairs.push((self.kind.as_str(), because));
        }
        crate::error::render_diagnostics("E-tix-wip", pairs)
    }
}

/// A set of WIP findings, reported together.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct WipError {
    diagnostics: Vec<WipDiagnostic>,
}

impl WipError {
    /// Wrap the findings.
    pub fn new(diagnostics: Vec<WipDiagnostic>) -> Self {
        Self { diagnostics }
    }

    /// A single finding.
    pub fn single(diagnostic: WipDiagnostic) -> Self {
        Self {
            diagnostics: vec![diagnostic],
        }
    }

    /// The findings, in the order they were found.
    pub fn diagnostics(&self) -> &[WipDiagnostic] {
        &self.diagnostics
    }

    /// The first finding.
    pub fn first(&self) -> &WipDiagnostic {
        self.diagnostics
            .first()
            .expect("a WipError carries at least one diagnostic")
    }

    /// Add a sentence to this error's **first** finding, when it is alone.
    pub fn because(self, because: impl Into<String>) -> Self {
        let mut diagnostics = self.diagnostics;
        if let Some(first) = diagnostics.first_mut() {
            first.because = Some(because.into());
        }
        Self { diagnostics }
    }

    /// Every finding as one rendered block.
    pub fn render(&self) -> String {
        self.diagnostics
            .iter()
            .map(WipDiagnostic::render)
            .collect::<Vec<_>>()
            .join("\n")
    }
}

impl std::fmt::Display for WipError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.render())
    }
}

impl std::error::Error for WipError {}

#[cfg(test)]
mod tests {
    #[allow(clippy::wildcard_imports)]
    use super::*;

    fn board_columns() -> Vec<String> {
        ["todo", "in progress", "in review", "done"]
            .into_iter()
            .map(String::from)
            .collect()
    }

    fn units(pairs: &[(&str, u32)]) -> IndexMap<String, u32> {
        pairs
            .iter()
            .map(|(name, factor)| ((*name).to_string(), *factor))
            .collect()
    }

    /// A board with `d`/`w` declared and one blocked limit on `in progress`.
    fn configured() -> WipConfig {
        WipConfig {
            units: units(&[("d", 1), ("w", 5)]),
            limits: IndexMap::from([(
                "in progress".to_string(),
                ColumnLimit {
                    max_items: Some(3),
                    max_estimate: Some(10),
                    unit: Some("d".to_string()),
                    policy: Some(LimitPolicy::Block),
                    enabled: true,
                },
            )]),
        }
    }

    #[test]
    fn wip_config_absent_limits_are_absent() {
        let empty = WipConfig::default();
        assert!(empty.is_empty());
        assert!(!empty.has_enabled_limits());
        assert!(empty.effective_limit("in progress").is_none());
        let toml = toml::to_string(&empty).expect("an empty section serializes");
        assert_eq!(toml.trim(), "", "an empty section writes no keys: {toml:?}");
        assert!(ColumnLimit::default().is_empty());
    }

    #[test]
    fn wip_config_round_trips_through_toml() {
        let config = configured();
        config.validate("default", &board_columns()).expect("valid");
        let text = toml::to_string(&config).expect("serializes");
        let back: WipConfig = toml::from_str(&text).expect("deserializes");
        assert_eq!(back, config, "round trip: {text}");
        assert!(back.has_enabled_limits());
    }

    #[test]
    fn wip_config_omits_defaults_on_save() {
        // A hand-written limit with neither `enabled` nor a unit it does not need
        // must come back byte-identical: no default key materializes.
        let text = "[limits.\"in progress\"]\nmax_items = 3\npolicy = \"warn\"\n";
        let config: WipConfig = toml::from_str(text).expect("loads");
        assert!(config.limits["in progress"].enabled, "default on");
        assert_eq!(toml::to_string(&config).expect("saves"), text);
    }

    #[test]
    fn wip_config_rejects_an_unknown_column() {
        let mut config = configured();
        config.limits.insert(
            "shipped".to_string(),
            ColumnLimit::items(1, LimitPolicy::Warn),
        );
        let error = config
            .validate("default", &board_columns())
            .expect_err("an unknown column is refused")
            .to_string();
        assert!(
            error.contains("kanban.default.wip.limits.`shipped`"),
            "{error}"
        );
        assert!(error.contains("columns"), "{error}");
    }

    #[test]
    fn wip_config_rejects_an_enabled_limit_that_limits_nothing() {
        let mut config = configured();
        config.limits.insert(
            "in review".to_string(),
            ColumnLimit {
                policy: Some(LimitPolicy::Warn),
                ..ColumnLimit::default()
            },
        );
        let error = config
            .validate("default", &board_columns())
            .expect_err("an enabled empty limit is refused")
            .to_string();
        assert!(
            error.contains("neither `max_items` nor `max_estimate`"),
            "{error}"
        );
    }

    #[test]
    fn wip_config_requires_a_policy_and_a_unit() {
        let mut missing_policy = configured();
        missing_policy.limits["in progress"].policy = None;
        let error = missing_policy
            .validate("default", &board_columns())
            .expect_err("a policy is required")
            .to_string();
        assert!(error.contains("policy` is required"), "{error}");

        let mut missing_unit = configured();
        missing_unit.limits["in progress"].unit = None;
        let error = missing_unit
            .validate("default", &board_columns())
            .expect_err("a unit is required with max_estimate")
            .to_string();
        assert!(error.contains("is required with `max_estimate`"), "{error}");

        let mut unit_without_estimate = configured();
        unit_without_estimate.limits["in progress"].max_estimate = None;
        let error = unit_without_estimate
            .validate("default", &board_columns())
            .expect_err("a unit without an estimate is refused")
            .to_string();
        assert!(
            error.contains("only meaningful with `max_estimate`"),
            "{error}"
        );
    }

    #[test]
    fn wip_config_rejects_undeclared_units_and_zero_factors() {
        let mut undeclared = configured();
        undeclared.limits["in progress"].unit = Some("q".to_string());
        let error = undeclared
            .validate("default", &board_columns())
            .expect_err("an undeclared unit is refused")
            .to_string();
        assert!(error.contains("`q`"), "{error}");
        assert!(error.contains("wip.units"), "{error}");

        let mut zero = configured();
        zero.units.insert("z".to_string(), 0);
        let error = zero
            .validate("default", &board_columns())
            .expect_err("a zero factor is refused")
            .to_string();
        assert!(error.contains("wip.units.z"), "{error}");
    }

    #[test]
    fn wip_config_zero_ceilings_are_refused() {
        for key in ["max_items", "max_estimate"] {
            let mut config = configured();
            let limit = config.limits.get_mut("in progress").expect("the limit");
            match key {
                "max_items" => limit.max_items = Some(0),
                _ => limit.max_estimate = Some(0),
            }
            let error = config
                .validate("default", &board_columns())
                .expect_err("a zero ceiling is refused")
                .to_string();
            assert!(error.contains(key), "{error}");
            assert!(error.contains("at least 1"), "{error}");
        }
    }

    #[test]
    fn wip_config_disabled_limit_is_validated_but_not_effective() {
        let mut config = configured();
        config.limits["in progress"].enabled = false;
        config.limits["in progress"].policy = None;
        config
            .validate("default", &board_columns())
            .expect("a disabled limit may state no policy");
        assert!(config.effective_limit("in progress").is_none());
        assert!(!config.has_enabled_limits());
        assert!(
            config.limits.contains_key("in progress"),
            "the numbers stay for later"
        );
    }

    #[test]
    fn wip_config_estimate_parsing_is_strict_but_total() {
        assert_eq!(
            Estimate::parse(" 3d ").expect("a unit"),
            Estimate {
                value: 3,
                unit: Some("d".to_string())
            }
        );
        assert_eq!(
            Estimate::parse("12").expect("a bare number"),
            Estimate {
                value: 12,
                unit: None
            }
        );
        assert_eq!(
            Estimate::parse("5story-points").expect("a hyphenated unit"),
            Estimate {
                value: 5,
                unit: Some("story-points".to_string())
            }
        );
        assert_eq!(
            Estimate::parse("1 day").expect("a prose unit"),
            Estimate {
                value: 1,
                unit: Some("d".to_string())
            }
        );
        assert_eq!(
            Estimate::parse("2 DAYS").expect("case-insensitive prose"),
            Estimate {
                value: 2,
                unit: Some("d".to_string())
            }
        );
        assert_eq!(
            Estimate::parse("3S").expect("a one-letter unit keeps its case"),
            Estimate {
                value: 3,
                unit: Some("S".to_string())
            }
        );
        assert_eq!(
            Estimate::parse("3.5").expect("a fraction rounds up"),
            Estimate {
                value: 4,
                unit: None
            }
        );
        for bad in [
            "",
            "twenty",
            "-2",
            "d3",
            "3d!",
            "3 2h",
            "1 day 2",
            "99999999999999",
        ] {
            let error = Estimate::parse(bad).expect_err("refused: {bad}");
            assert_eq!(error.first().kind, WipDiagnosticKind::MalformedEstimate);
        }
    }

    #[test]
    fn wip_config_estimate_parses_compound_durations_term_by_term() {
        let terms = Estimate::parse_terms("3 weeks 2 hours").expect("two terms");
        assert_eq!(
            terms,
            vec![
                Estimate {
                    value: 3,
                    unit: Some("w".to_string())
                },
                Estimate {
                    value: 2,
                    unit: Some("h".to_string())
                },
            ]
        );
        assert_eq!(
            Estimate::parse_terms("1d, 30 min").expect("comma-separated"),
            vec![
                Estimate {
                    value: 1,
                    unit: Some("d".to_string())
                },
                Estimate {
                    value: 30,
                    unit: Some("m".to_string())
                },
            ]
        );
        assert!(
            Estimate::parse("3 weeks 2 hours").is_err(),
            "the single-term entry point still names one term"
        );
    }

    #[test]
    fn wip_config_estimate_ranges_are_pessimistic() {
        assert_eq!(
            Estimate::parse("0.5-1 day").expect("a range"),
            Estimate {
                value: 1,
                unit: Some("d".to_string())
            }
        );
        assert_eq!(
            Estimate::parse("0.5 day").expect("a fraction rounds up"),
            Estimate {
                value: 1,
                unit: Some("d".to_string())
            }
        );
        assert_eq!(
            Estimate::parse("2.1-2.2d").expect("the upper bound, rounded up"),
            Estimate {
                value: 3,
                unit: Some("d".to_string())
            }
        );
        assert_eq!(
            Estimate::parse("2-1 day").expect("the larger bound wins"),
            Estimate {
                value: 2,
                unit: Some("d".to_string())
            }
        );
    }

    #[test]
    fn wip_config_estimate_ignores_unreadable_comma_annotations() {
        assert_eq!(
            Estimate::parse_terms("~300 LOC, 0.5-1 day").expect("the estimate segment"),
            vec![Estimate {
                value: 1,
                unit: Some("d".to_string())
            }]
        );
        assert_eq!(
            Estimate::parse_terms("3d, best guess").expect("the first segment"),
            vec![Estimate {
                value: 3,
                unit: Some("d".to_string())
            }]
        );
        assert!(
            Estimate::parse_terms("~300 LOC").is_err(),
            "no readable segment means malformed"
        );
    }

    #[test]
    fn wip_config_sums_compound_estimates_through_the_board_units() {
        let config = WipConfig {
            units: units(&[("h", 1), ("d", 8), ("w", 40)]),
            limits: IndexMap::new(),
        };
        let terms = Estimate::parse_terms("3 weeks 2 hours").expect("parses");
        assert_eq!(
            config.convert_terms(&terms, "h").expect("exact"),
            3 * 5 * 8 + 2,
            "a prose estimate is board-relative, never a clock-ratio guess"
        );
        // One unconvertible term refuses the whole sum; nothing is dropped.
        let terms = Estimate::parse_terms("1 day 30 fortnights").expect("parses");
        let error = config
            .convert_terms(&terms, "h")
            .expect_err("the second unit is undeclared");
        assert_eq!(error.first().kind, WipDiagnosticKind::MissingConversion);
    }

    #[test]
    fn wip_config_converts_between_declared_units() {
        let config = configured();
        let weeks = Estimate {
            value: 1,
            unit: Some("w".to_string()),
        };
        assert_eq!(config.convert(&weeks, "d").expect("1w is 5d"), 5);
        assert_eq!(
            config
                .convert(&Estimate::parse("10d").expect("parses"), "d")
                .expect("same unit"),
            10
        );
        assert_eq!(
            config
                .convert(&Estimate::parse("7").expect("parses"), "w")
                .expect("bare means the target unit"),
            7
        );
        let half_weeks = Estimate {
            value: 5,
            unit: Some("w".to_string()),
        };
        assert_eq!(
            config.convert(&half_weeks, "w").expect("same unit"),
            5,
            "5w is 5w"
        );
        assert_eq!(config.convert(&half_weeks, "d").expect("25 points"), 25);
    }

    #[test]
    fn wip_config_refuses_a_missing_conversion() {
        let config = configured();
        let points = Estimate {
            value: 3,
            unit: Some("p".to_string()),
        };
        let error = config.convert(&points, "d").expect_err("undeclared unit");
        assert_eq!(error.first().kind, WipDiagnosticKind::MissingConversion);
        let rendered = error.render();
        assert!(rendered.contains("missing_conversion"), "{rendered}");
        assert!(rendered.contains("`3p`"), "{rendered}");

        let error = config
            .convert(&Estimate::parse("3").expect("parses"), "q")
            .expect_err("an undeclared target unit");
        assert_eq!(error.first().kind, WipDiagnosticKind::UnknownUnit);
    }

    #[test]
    fn wip_config_refuses_a_fractional_conversion() {
        // A board whose base is `h`: `d` is 8, so 3d is 24h; counting that in `w`
        // (a 5-hour unit) is not a whole number and must not be rounded.
        let config = WipConfig {
            units: units(&[("h", 1), ("d", 8), ("w", 40)]),
            limits: IndexMap::new(),
        };
        let error = config
            .convert(&Estimate::parse("3d").expect("parses"), "w")
            .expect_err("24 is not a whole number of 5");
        assert_eq!(error.first().kind, WipDiagnosticKind::AmbiguousConversion);
        let rendered = error.render();
        assert!(rendered.contains("ambiguous_conversion"), "{rendered}");
        assert!(rendered.contains("24 base points"), "{rendered}");
        // …and the same estimate in `h` is exact.
        assert_eq!(
            config
                .convert(&Estimate::parse("3d").expect("parses"), "h")
                .expect("24h"),
            24
        );
    }

    #[test]
    fn wip_config_policy_spellings_are_stable() {
        assert_eq!(LimitPolicy::Warn.as_str(), "warn");
        assert_eq!(LimitPolicy::Block.as_str(), "block");
        let limit = configured().limits["in progress"].clone();
        assert_eq!(limit.resolved_policy(), Some(LimitPolicy::Block));
        let disabled = ColumnLimit {
            enabled: false,
            ..limit
        };
        assert_eq!(disabled.resolved_policy(), None);
    }
}