tix-tracker 0.11.0

//! The TUI batch surface (WP07).
//!
//! Everything here is a **state machine over shared services**. It builds no patch
//! and writes no file: the selection goes through `bulk::Selection::from_issues`
//! (WP01's constructor, built for exactly this), the preview through
//! `bulk::plan::build_plan`, the apply through `bulk::apply`/`bulk::pair`/
//! `bulk::archive`, and the text through `commands::bulk`'s **same** renderers the
//! CLI uses.
//!
//! ## Why the TUI holds `PatchFlags` and not an `IssuePatch`
//!
//! T032 says to "reject TUI-local patch construction or direct writes". A TUI that
//! built its own `IssuePatch` would be a second mapping from user input to a typed
//! patch, free to drift from the CLI's — and the drift would show up as a TUI
//! accepting a blank field as `Clear` while the CLI treats it as absent, which is
//! precisely the bug WP06 found in the CLI.
//!
//! So the modal holds `commands::bulk::PatchFlags` — the **same** struct the CLI
//! parses into — and the conversion happens in one place. The TUI's only job is to
//! set flags and press apply.
//!
//! ## The board cursor is untouched
//!
//! T031 requires the existing single-card cursor and navigation semantics to stay
//! intact. So the multi-selection is a **separate** ordered set, and the board's
//! `(active_col, selected)` pair is never written by anything in this module. That is
//! also what makes cancelling safe: the modal is a value, and dropping it restores
//! the board exactly.
//!
//! ## Why there is a focus, and not one key channel
//!
//! A first draft had `p` preview, `y` confirm, `c` clear **and** bare characters as
//! field text, all on one channel. That is not a shortcut, it is a bug: typing `p`
//! into the status field previews instead of typing. Any single-channel design has
//! this — the union of "characters a field may contain" and "keys that are commands"
//! is the whole ASCII range.
//!
//! So the modal has [`BulkFocus`], the same two-state shape the settings prompt already
//! uses (`InputContext::SettingsPrompt`). On a **row** the keys are commands; in
//! **edit** they are text. `enter` moves between them, and the two never overlap.
//!
//! ## The same text as the CLI
//!
//! `render_preview` and `render_result` call `commands::bulk::render_plan` and
//! `render_report`. `contracts/surface-parity.md` requires the same decision and the
//! same message on every surface, and the cheapest way to guarantee that is not to
//! have two renderers.

use ratatui::Frame;
use ratatui::layout::{Constraint, Direction, Layout, Rect};
use ratatui::style::{Modifier, Style};
use ratatui::text::{Line, Span};
use ratatui::widgets::{Block, Borders, Clear, List, ListItem, Paragraph};

use crate::bulk::plan::BatchPlan;
use crate::bulk::{
    self, ApplyReport, ArchiveRequest, Confirmation, IssuePatch, RelationshipOp, Selection,
};
use crate::commands::bulk::{self as cli_bulk, Mode, PatchFlags};
use crate::error::{Result, TixError};
use crate::storage::Store;

/// Which batch action a modal is for.
///
/// **Not** `cli::BulkAction`. That enum carries every flag as struct fields — the
/// flags are the clap surface, and the modal *is* the flags. Storing it would put
/// each flag in two places and let them disagree, which is the T032 prohibition
/// ("reject TUI-local patch construction") in a different guise. Four words, and the
/// `From` impl is the only conversion.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum BatchAction {
    Edit,
    Link,
    Unlink,
    Archive,
}

impl BatchAction {
    /// The word a user reads.
    pub fn as_str(self) -> &'static str {
        match self {
            Self::Edit => "edit",
            Self::Link => "link",
            Self::Unlink => "unlink",
            Self::Archive => "archive",
        }
    }

    /// Whether this action takes field flags, as opposed to a target and a kind.
    pub fn takes_fields(self) -> bool {
        matches!(self, Self::Edit)
    }

    /// Whether this action is a pair.
    pub fn is_pair(self) -> bool {
        matches!(self, Self::Link | Self::Unlink)
    }

    /// The next action, for the cycle key.
    ///
    /// A fixed order — edit, link, unlink, archive — so `a` twice returns to where
    /// it started. A cycle whose order depended on the board would make `a` a
    /// non-repeatable key, and a non-repeatable cycle is a key nobody uses twice.
    pub fn next(self) -> Self {
        match self {
            Self::Edit => Self::Link,
            Self::Link => Self::Unlink,
            Self::Unlink => Self::Archive,
            Self::Archive => Self::Edit,
        }
    }
}

impl From<&crate::cli::BulkAction> for BatchAction {
    fn from(action: &crate::cli::BulkAction) -> Self {
        match action {
            crate::cli::BulkAction::Edit { .. } => Self::Edit,
            crate::cli::BulkAction::Link { .. } => Self::Link,
            crate::cli::BulkAction::Unlink { .. } => Self::Unlink,
            crate::cli::BulkAction::Archive { .. } => Self::Archive,
        }
    }
}

/// The largest a batch selection may be.
///
/// A bound, and stated, because a TUI selection is built by **toggling cards** and
/// there is no "press enter to start" moment at which a user has said "all of these".
/// A board of 1200 issues would let a user mark 1200 of them with 1200 keystrokes
/// and then be asked to confirm a 1200-item write with a `y`.
///
/// So the selection is bounded, `toggle` **refuses** past the bound rather than
/// silently dropping, and the refusal says the bound. A bound the user cannot reach
/// is worse than no bound, so it is a refusal with a number in it — and the number is
/// this constant, not a literal at the call site.
pub const MAX_BATCH_SELECTION: usize = 200;

/// Why a selection operation was refused.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum SelectionProblem {
    /// The bound above.
    TooLarge,
    /// The same issue twice.
    AlreadySelected,
}

impl SelectionProblem {
    pub fn as_str(self) -> &'static str {
        match self {
            Self::TooLarge => "selection_full",
            Self::AlreadySelected => "already_selected",
        }
    }
}

impl std::fmt::Display for SelectionProblem {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::TooLarge => write!(
                f,
                "a batch selection holds at most {MAX_BATCH_SELECTION} issues — \
                 clear some first, or narrow the filter"
            ),
            Self::AlreadySelected => {
                write!(f, "that issue is already selected — press `x` to remove it")
            }
        }
    }
}

/// The multi-selection: an ordered, de-duplicated set of issue numbers.
///
/// **Order is the order the user marked them**, not the board's column order, and not
/// numeric order. A user marks what they can see, and a plan that reorders what they
/// marked is a plan they did not read.
#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct BulkSelection {
    numbers: Vec<u32>,
}

impl BulkSelection {
    pub fn new() -> Self {
        Self::default()
    }

    /// Add an issue, refusing a duplicate and refusing past the bound.
    ///
    /// Both refusals are `Err` rather than a silent `false`, because a silent `false`
    /// for "too many" is a keystroke that appeared to do nothing, and a user
    /// counting their selection has no way to know which press was dropped.
    pub fn toggle(&mut self, number: u32) -> std::result::Result<bool, SelectionProblem> {
        if self.numbers.contains(&number) {
            return Err(SelectionProblem::AlreadySelected);
        }
        if self.numbers.len() >= MAX_BATCH_SELECTION {
            return Err(SelectionProblem::TooLarge);
        }
        self.numbers.push(number);
        Ok(true)
    }

    /// Remove an issue, reporting whether it was there.
    ///
    /// `bool` rather than `Result`: removing something that is not selected is the
    /// *desired* end state, and a user pressing `x` twice means "not selected", not
    /// "something went wrong".
    pub fn remove(&mut self, number: u32) -> bool {
        let before = self.numbers.len();
        self.numbers.retain(|n| *n != number);
        self.numbers.len() != before
    }

    /// Remove everything.
    pub fn clear(&mut self) {
        self.numbers.clear();
    }

    pub fn contains(&self, number: u32) -> bool {
        self.numbers.contains(&number)
    }

    /// The numbers, in the order the user marked them.
    pub fn numbers(&self) -> &[u32] {
        &self.numbers
    }

    pub fn len(&self) -> usize {
        self.numbers.len()
    }

    pub fn is_empty(&self) -> bool {
        self.numbers.is_empty()
    }

    /// The one-line header a surface shows.
    ///
    /// The count **and** the bound, so a user who hit the ceiling can see where they
    /// are without counting the marks themselves.
    pub fn summary(&self) -> String {
        if self.numbers.is_empty() {
            return "no issues selected — press `space` on a card, `X` to clear".to_string();
        }
        let list: Vec<String> = self.numbers.iter().map(u32::to_string).collect();
        format!(
            "{} selected (#{}) of at most {MAX_BATCH_SELECTION}",
            self.numbers.len(),
            list.join(", ")
        )
    }

    /// The `Selection` a plan is built from, in the marked order.
    ///
    /// Takes the issues rather than a store, because the TUI already has them: it
    /// has read the board to draw the cards. Re-resolving through selectors would be
    /// a second selection path, and it would produce a *different* order.
    ///
    /// Issues whose number is not in `issues` are **dropped** rather than refused.
    /// The board may have been filtered between marking and previewing, and a
    /// preview that refuses because a card went out of view is a preview the user
    /// cannot get at all. The dropped number is reported in the note, so "3 of your
    /// 5 are still visible" is visible rather than inferred.
    pub fn to_selection(&self, issues: &[(u32, crate::model::Issue)]) -> (Selection, Vec<u32>) {
        let mut kept = Vec::new();
        let mut dropped = Vec::new();
        for number in &self.numbers {
            if issues.iter().any(|(n, _)| n == number) {
                kept.push(*number);
            } else {
                dropped.push(*number);
            }
        }
        let selection = Selection::from_issues(
            kept.iter().filter_map(|number| {
                issues
                    .iter()
                    .find(|(n, _)| n == number)
                    .map(|(_, issue)| issue.clone())
            }),
            bulk::SelectionSource::Explicit,
            bulk::SelectionScope::Active,
        );
        (selection, dropped)
    }
}

/// Where the modal is in its own cycle.
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum BulkState {
    /// Choosing issues.
    Selecting,
    /// A plan is built and shown. Cancelling here changes nothing — it never has.
    Preview(Box<BatchPlan>),
    /// The plan is shown and awaiting an explicit confirm. **Separate** from
    /// `Preview` so the modal can render a different affordance, and so "I saw it" and
    /// "I approved it" are two different states in the record rather than one.
    Confirming(Box<BatchPlan>),
    /// The batch ran. Per-item outcomes are in the report.
    Done(Box<ApplyReport>, String),
    /// The batch was refused before or during the apply.
    Refused(String),
    /// An action needs something the user has not given (a pair's target).
    NeedsInput(&'static str),
}

/// Which channel the keys belong to.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum BulkFocus {
    /// The key is a command (`p`, `y`, `a`, `x`, `X`, `c`).
    Row,
    /// The key is text for the row under the cursor.
    Edit,
}

/// The batch modal.
#[derive(Debug, Clone)]
pub struct BulkModal {
    pub action: BatchAction,
    /// The **CLI's** flag struct, not a locally built patch (see the module docs).
    pub flags: PatchFlags,
    /// The other end of a pair.
    pub target: Option<String>,
    /// The relationship kind, as the user will set it.
    pub kind: Option<String>,
    /// Which row the cursor is on.
    pub cursor: usize,
    pub focus: BulkFocus,
    /// The text being typed, while `focus` is [`BulkFocus::Edit`].
    ///
    /// A draft is **discarded** on `esc`, never committed. An earlier draft of this
    /// modal snapshotted the row on `begin_edit` and restored it on `esc`; the
    /// snapshot was dead — `commit_edit` is the only thing that writes a row, so the
    /// restore and a clear were indistinguishable from outside. The revert-and-red
    /// run is what proved it: a mutation replacing the restore with a clear left all
    /// 141 cases green.
    pub draft: String,
    pub selection: BulkSelection,
    pub state: BulkState,
    /// The last message, for the status bar.
    pub note: Option<String>,
    /// Whether the plan no longer matches the screen.
    ///
    /// Set on the first preview and on **any** change to the selection or the flags,
    /// so a confirm can never apply a plan the user has not looked at.
    pub plan_stale: bool,
}

impl BulkModal {
    /// A fresh modal for `action`.
    pub fn new(action: BatchAction) -> Self {
        Self {
            action,
            flags: PatchFlags::default(),
            target: None,
            kind: None,
            cursor: 0,
            focus: BulkFocus::Row,
            draft: String::new(),
            selection: BulkSelection::new(),
            state: BulkState::Selecting,
            note: None,
            plan_stale: true,
        }
    }

    /// The row names, in the order `tab` walks them.
    ///
    /// Depends on the action, and that is the point: an archive has **no** rows,
    /// because `ArchiveRequest::archive()` names no target status and inventing a
    /// field for one would be offering a restore that #190's C-003 does not allow.
    /// A pair has no field rows either — it has a target and a kind.
    pub fn row_names(&self) -> Vec<&'static str> {
        let mut names: Vec<&'static str> = if self.action.takes_fields() {
            PatchFlags::field_rows().to_vec()
        } else {
            Vec::new()
        };
        if self.action.is_pair() {
            names.push("target");
            names.push("kind");
        }
        names
    }

    /// The name of the row at `index`, for the render.
    pub fn row_name(&self, index: usize) -> &'static str {
        self.row_names()
            .into_iter()
            .nth(index)
            .unwrap_or("selection")
    }

    /// The value of the row at `index`.
    ///
    /// An absent value is the em dash, not an empty string, so a blank row is
    /// visibly blank rather than looking like a field set to `""`. The distinction is
    /// the whole WP06 finding: a blank `--estimate ""` is `Unchanged`.
    pub fn row_value(&self, index: usize) -> String {
        let flags = &self.flags;
        match self.row_name(index) {
            "status" => flags.status.clone(),
            "priority" => flags.priority.clone(),
            "assignee" => flags.assignee.clone(),
            "labels" => flags.labels.clone(),
            "start-date" => flags.start_date.clone(),
            "due-date" => flags.due_date.clone(),
            "estimate" => flags.estimate.clone(),
            "cycles" => flags.cycles.clone(),
            "milestones" => flags.milestones.clone(),
            "clear" => (!flags.clear.is_empty()).then(|| flags.clear.join(" ")),
            "target" => self.target.clone(),
            "kind" => self.kind.clone(),
            _ => None,
        }
        .unwrap_or_else(|| "—".to_string())
    }

    /// Store `value` on the row at `index`, or say why it cannot be stored.
    ///
    /// A blank value is stored as **absent** (`None`), which is what makes "the user
    /// cleared the field" and "the user never touched it" the same request — the
    /// contract's `Unchanged`. The `clear` row is the *explicit* way to empty
    /// something, and it is the only row that may name a field `clear` does not own.
    pub fn set_row(&mut self, index: usize, value: String) -> Result<()> {
        let value = value.trim().to_string();
        let name = self.row_name(index);
        let flags = &mut self.flags;
        let slot = match name {
            "status" => &mut flags.status,
            "priority" => &mut flags.priority,
            "assignee" => &mut flags.assignee,
            "labels" => &mut flags.labels,
            "start-date" => &mut flags.start_date,
            "due-date" => &mut flags.due_date,
            "estimate" => &mut flags.estimate,
            "cycles" => &mut flags.cycles,
            "milestones" => &mut flags.milestones,
            "clear" => {
                if value.is_empty() {
                    flags.clear.clear();
                    self.mark_stale();
                    return Ok(());
                }
                if !PatchFlags::is_clearable(&value) {
                    return Err(TixError::InvalidInput(format!(
                        "cannot clear '{value}' — clearable fields: {}",
                        PatchFlags::clearable().join(", ")
                    )));
                }
                // One `--clear` per invocation, exactly as the CLI carries it. A second
                // field is **refused**, not appended and not dropped — a `--clear a
                // --clear b` that silently honoured only `a` is a request half-met.
                if !flags.clear.is_empty() && !flags.clear.contains(&value) {
                    return Err(TixError::InvalidInput(format!(
                        "one batch clears one field — '{value}' is clearable, and '{}' is \
                         already named; clear them one run at a time",
                        flags.clear[0]
                    )));
                }
                flags.clear = vec![value];
                self.mark_stale();
                return Ok(());
            }
            "target" => {
                let slot = &mut self.target;
                *slot = (!value.is_empty()).then_some(value);
                self.mark_stale();
                return Ok(());
            }
            "kind" => {
                let slot = &mut self.kind;
                *slot = (!value.is_empty()).then_some(value);
                self.mark_stale();
                return Ok(());
            }
            _ => return Ok(()),
        };
        *slot = (!value.is_empty()).then_some(value);
        self.mark_stale();
        Ok(())
    }

    /// Mark that the plan no longer matches the screen.
    ///
    /// `contracts/patch-plan.md` §4: "Apply requires the exact confirmed plan … any
    /// change to selection or patch requires a new preview." So a confirm is refused
    /// while stale, and the refusal says *why* rather than silently re-previewing — a
    /// silent re-preview would apply something the user did not look at.
    pub fn mark_stale(&mut self) {
        self.plan_stale = true;
    }

    /// Begin editing the row under the cursor.
    pub fn begin_edit(&mut self) {
        let row = self.cursor;
        self.draft = self.row_value(row);
        // A row that was never set starts empty, not showing the em dash the user
        // would then have to delete before typing.
        if self.draft == "—" {
            self.draft.clear();
        }
        self.focus = BulkFocus::Edit;
    }

    /// Commit the draft, or report why it cannot be committed.
    pub fn commit_edit(&mut self) -> Result<()> {
        let row = self.cursor;
        let draft = std::mem::take(&mut self.draft);
        self.focus = BulkFocus::Row;
        self.set_row(row, draft)
    }

    /// Abandon the draft. The row keeps whatever it had.
    ///
    /// Discarding rather than committing is the point: an abandoned edit that still
    /// wrote the half-typed value is an abandoned edit that changed state. The draft
    /// is thrown away rather than left in place, because `begin_edit` rebuilds it
    /// from the row every time — so a leftover draft is a draft nothing can read.
    pub fn abort_edit(&mut self) {
        self.draft.clear();
        self.focus = BulkFocus::Row;
    }

    /// Move the cursor, wrapping. A no-op when the action has no rows (an archive).
    pub fn move_cursor(&mut self, delta: isize) {
        let count = self.row_names().len();
        if count == 0 {
            self.cursor = 0;
            return;
        }
        let len = count as isize;
        let next = (self.cursor as isize + delta).rem_euclid(len);
        self.cursor = next as usize;
    }

    /// The typed patch for a **field** action, or say why it cannot be built.
    ///
    /// Delegates to the CLI's own conversion, so a TUI field and a CLI flag mean the
    /// same thing — including the "a blank field is `Unchanged`, not `Clear`" rule
    /// WP06 found. A TUI that built its own patch would have its own blank rule.
    pub fn patch(&self) -> Result<IssuePatch> {
        self.flags.to_patch()
    }

    /// The typed patch for **this** action, or say why it cannot be built.
    ///
    /// One method, because the preview and the confirm both need it, and two
    /// `match self.action` blocks are two places for an action to be handled
    /// differently.
    pub fn patch_for(&self) -> Result<IssuePatch> {
        Ok(match self.action {
            BatchAction::Edit => self.patch()?,
            BatchAction::Link | BatchAction::Unlink => IssuePatch {
                relationship: Some(self.relationship_for(&[], None)?),
                ..IssuePatch::default()
            },
            BatchAction::Archive => IssuePatch {
                archive: Some(self.archive_request()),
                ..IssuePatch::default()
            },
        })
    }

    /// Build a plan for the current selection. Read-only by construction: it
    /// resolves, validates and renders a preview, and writes nothing.
    pub fn preview(&mut self, store: &Store, issues: &[(u32, crate::model::Issue)]) -> Result<()> {
        if self.selection.is_empty() {
            self.state = BulkState::NeedsInput("select at least one issue with `space`");
            return Ok(());
        }
        // A request the modal cannot turn into a plan is a **refusal**, not an `Err`.
        // WP06 froze that rule for the CLI — "a refusal is a completed command that
        // reports non-zero, its reasons go to stdout" — and the TUI is a surface of
        // the same command, so it gets the same rule. An `Err` out of `preview` would
        // leave the event loop with a `Result` to do something about, and the only
        // sensible thing it could do is quit: a user who pressed `p` with no field set
        // would lose their board.
        let patch = match self.patch_for() {
            Ok(patch) => patch,
            Err(e) => {
                self.state = BulkState::Refused(e.to_string());
                self.note = Some(e.to_string());
                return Ok(());
            }
        };
        let (selection, dropped) = self.selection.to_selection(issues);
        if selection.is_empty() {
            self.state = BulkState::NeedsInput("none of the selected issues are on the board");
            return Ok(());
        }
        let plan = match bulk::plan::build_plan(
            &store.config,
            &store.issues_dir,
            selection,
            patch,
            |op: &RelationshipOp| bulk::pair::plan_for(store, op),
        )
        .map(|mut plan| {
            // WP07 T035: the modal's preview shows the same WIP decisions the apply
            // will, from the **store's** issues (a column counts every card in it,
            // not only the selected ones).
            crate::wip::bulk::annotate_plan(
                &mut plan,
                &store.config,
                &store.list().unwrap_or_default(),
            );
            plan
        }) {
            Ok(plan) => plan,
            Err(e) => {
                self.state = BulkState::Refused(e.to_string());
                self.note = Some(e.to_string());
                return Ok(());
            }
        };
        self.note = (!dropped.is_empty()).then(|| {
            format!(
                "{} selected issue(s) are no longer on the board and were left out: #{}",
                dropped.len(),
                dropped
                    .iter()
                    .map(u32::to_string)
                    .collect::<Vec<_>>()
                    .join(", #")
            )
        });
        self.state = BulkState::Preview(Box::new(plan));
        self.plan_stale = false;
        Ok(())
    }

    /// The relationship operation for `numbers`, or the field the user has not filled
    /// in.
    ///
    /// A pair's `from` is **per selected issue**, not the whole selection: `from` is a
    /// single issue in the relationship vocabulary, and the batch is the set of
    /// edges. Passing the whole selection as `from` would build a plan for an edge
    /// that does not exist.
    pub fn relationship_for(
        &self,
        numbers: &[u32],
        kind_override: Option<String>,
    ) -> Result<RelationshipOp> {
        let target = self
            .target
            .as_deref()
            .map(str::trim)
            .filter(|t| !t.is_empty())
            .ok_or_else(|| {
                TixError::InvalidInput("a pair needs a target — edit the `target` row".to_string())
            })?;
        // The kind is the **service's** vocabulary, through its own parser, so a TUI
        // kind is a value `tix link --type` would accept.
        let kind = match kind_override {
            Some(raw) => crate::commands::link::require_kind(Some(raw.as_str()))?,
            None => crate::commands::link::require_kind(self.kind.as_deref())?,
        };
        // A preview of a whole selection has no single `from`; the caller pairs each
        // issue separately. An empty `numbers` means "the caller is previewing the
        // shape", and the pair's target and kind are all it needs.
        let from = numbers.first().map(u32::to_string).unwrap_or_default();
        Ok(if self.action == BatchAction::Unlink {
            RelationshipOp::unlink(from, target, kind)
        } else {
            RelationshipOp::link(from, target, kind)
        })
    }

    /// The archive request.
    ///
    /// The TUI's archive action is **archive only** — there is no restore verb on
    /// this modal, because a restore needs an explicit target status (#190's C-003)
    /// and there is no row for one. A modal that offered a restore with no target
    /// would be offering the request #190 rejects.
    pub fn archive_request(&self) -> ArchiveRequest {
        ArchiveRequest::archive()
    }

    /// Go from a shown plan to the confirming state.
    ///
    /// Two steps rather than one, because "I saw it" and "I approved it" are two
    /// different decisions and a single `y` conflates them. The confirming state
    /// renders a different affordance, so the user can see which one they are in.
    pub fn arm(&mut self) {
        if let BulkState::Preview(plan) = &self.state {
            self.state = BulkState::Confirming(plan.clone());
        }
    }

    /// Whether the modal is armed — the state in which `y` writes.
    pub fn is_armed(&self) -> bool {
        matches!(self.state, BulkState::Confirming(_))
    }

    /// Confirm the plan that is on screen and apply it.
    ///
    /// Refuses while the plan is **stale**, and the refusal says why. That is
    /// contract §4's "any change to selection or patch requires a new preview", and
    /// it is checked here rather than inside the apply so a TUI user gets a TUI
    /// message.
    pub fn confirm(&mut self, store: &Store) -> Result<()> {
        if self.plan_stale {
            return Err(TixError::InvalidInput(
                "the selection or the fields changed since the preview — press `p` \
                 again to see what would happen now"
                    .to_string(),
            ));
        }
        let (BulkState::Confirming(plan) | BulkState::Preview(plan)) = &self.state else {
            return Err(TixError::InvalidInput(
                "nothing to confirm — press `p` to preview first".to_string(),
            ));
        };
        let mut confirmed = (**plan).clone();
        confirmed.confirmation = Some(Confirmation::issue(plan));
        let text = match self.action {
            BatchAction::Edit => {
                let report =
                    bulk::apply_fields(store, &confirmed, &crate::storage::actor_identity(), None)?;
                let text = cli_bulk::render_report(&report, &confirmed, Mode::Apply);
                self.state = BulkState::Done(Box::new(report), text.clone());
                text
            }
            BatchAction::Link | BatchAction::Unlink => {
                let text = self.apply_pairs(store, &confirmed);
                self.state = BulkState::Refused(text.clone());
                text
            }
            BatchAction::Archive => {
                // The archive direction, through the **same** `apply_archive` the CLI
                // and MCP use: the store's archive service renames each selected file
                // in place and appends one History event, and the per-item outcomes are
                // the shared vocabulary. A stale-plan check already ran above, and the
                // confirmation is set for the same reason the edit branch sets it.
                //
                // The result is a `Done` report, exactly as an edit batch: the user
                // pressed `y` to apply, so the honest answer is what each issue became,
                // not a refusal screen.
                let report = bulk::apply_archive(store, &confirmed)?;
                let text = cli_bulk::render_report(&report, &confirmed, Mode::Apply);
                self.state = BulkState::Done(Box::new(report), text.clone());
                text
            }
        };
        self.note = text.lines().next().map(str::to_string);
        Ok(())
    }

    /// One plan and one apply per selected issue, for a pair.
    ///
    /// Per issue rather than one batched pair because `from` is a single issue in the
    /// relationship vocabulary. Each issue goes through the same `build_plan` +
    /// `apply_pair` the CLI uses, so a mixed result is a per-issue line and a
    /// refusal names the issue it refused.
    fn apply_pairs(&self, store: &Store, plan: &BatchPlan) -> String {
        let mut lines = Vec::new();
        let mut applied = 0usize;
        let mut refused = 0usize;
        for issue in plan.selection.issues() {
            let numbers = [issue.number];
            let outcome = match self.relationship_for(&numbers, None) {
                Ok(op) => {
                    let per_issue = bulk::plan::build_plan(
                        &store.config,
                        &store.issues_dir,
                        Selection::from_issues(
                            vec![issue.clone()],
                            bulk::SelectionSource::Explicit,
                            bulk::SelectionScope::Active,
                        ),
                        IssuePatch {
                            relationship: Some(op.clone()),
                            ..IssuePatch::default()
                        },
                        |o: &RelationshipOp| bulk::pair::plan_for(store, o),
                    );
                    match per_issue {
                        Ok(mut per_issue) => {
                            per_issue.confirmation = Some(Confirmation::issue(&per_issue));
                            match bulk::apply_pair(store, &per_issue) {
                                Ok(outcome) => {
                                    if outcome.is_applied() {
                                        applied += 1;
                                    } else {
                                        refused += 1;
                                    }
                                    outcome.as_line()
                                }
                                Err(e) => {
                                    refused += 1;
                                    format!("refused: {e}")
                                }
                            }
                        }
                        Err(e) => {
                            refused += 1;
                            format!("refused: {e}")
                        }
                    }
                }
                Err(e) => {
                    refused += 1;
                    format!("refused: {e}")
                }
            };
            lines.push(format!("#{} {} — {outcome}", issue.number, issue.title));
        }
        lines.push(String::new());
        lines.push(format!(
            "{applied} relationship operation{} applied, {refused} refused",
            if applied == 1 { "" } else { "s" }
        ));
        lines.join("\n")
    }

    /// Back to choosing, from any state.
    ///
    /// **`confirm` is the only method here that writes**, so cancelling from any other
    /// state cannot have changed a file. The confirm state keeps its plan so a
    /// mis-aimed `esc` does not throw away a preview the user wanted to look at
    /// again.
    pub fn cancel(&mut self) {
        self.state = BulkState::Selecting;
        self.focus = BulkFocus::Row;
        self.draft.clear();
        self.plan_stale = true;
    }

    /// The state, in the words a user reads.
    pub fn state_label(&self) -> &'static str {
        match self.state {
            BulkState::Selecting => "choosing",
            BulkState::Preview(_) => "preview — nothing written",
            BulkState::Confirming(_) => "confirming — y writes",
            BulkState::Done(..) => "done",
            BulkState::Refused(_) => "refused",
            BulkState::NeedsInput(_) => "needs input",
        }
    }

    /// The rows, as the modal shows them: a cursor, a name and a value.
    pub fn rows(&self) -> Vec<(bool, String, String)> {
        self.row_names()
            .into_iter()
            .enumerate()
            .map(|(index, name)| {
                let value = if self.focus == BulkFocus::Edit && index == self.cursor {
                    format!("{}█", self.draft)
                } else {
                    self.row_value(index)
                };
                (index == self.cursor, name.to_string(), value)
            })
            .collect()
    }

    /// The footer, naming the keys that mean something **right now**.
    ///
    /// The list is per-focus and per-state, because a footer that names `y` while `y`
    /// types a letter is a footer that teaches the wrong thing.
    pub fn footer(&self) -> String {
        if self.focus == BulkFocus::Edit {
            return "enter commit · esc revert".to_string();
        }
        match (&self.state, self.action) {
            (BulkState::Preview(_), _) => {
                "y to confirm · p to re-preview · esc to cancel".to_string()
            }
            (BulkState::Confirming(_), _) => "y APPLIES THIS WRITE · esc to cancel".to_string(),
            (_, BatchAction::Edit) => {
                "space mark · x unmark · X clear · c clear field · enter edit · a action · p preview · esc cancel"
                    .to_string()
            }
            _ => "enter edit · a action · p preview · esc cancel".to_string(),
        }
    }

    /// The text a surface shows for the current state, from the **CLI's** renderers.
    pub fn body(&self) -> String {
        match &self.state {
            BulkState::Selecting => {
                let mut out = self.selection.summary();
                let rows = self.rows();
                if rows.is_empty() {
                    out.push_str(&format!(
                        "\nno fields to fill in for {} — the selection is the whole request\n",
                        self.action.as_str()
                    ));
                } else {
                    out.push_str("\nfields (enter to edit):\n");
                    for (on, name, value) in rows {
                        let cursor = if on { ">" } else { " " };
                        out.push_str(&format!("{cursor} {name}: {value}\n"));
                    }
                }
                if let Some(note) = &self.note {
                    out.push_str(&format!("\nnote: {note}\n"));
                }
                out.push_str(&format!("\n{}", self.footer()));
                out
            }
            BulkState::Preview(plan) => {
                let mut out = cli_bulk::render_plan(plan, Mode::Preview);
                if let Some(note) = &self.note {
                    out.push_str(&format!("\nnote: {note}"));
                }
                out.push('\n');
                out.push_str(&self.footer());
                out
            }
            BulkState::Confirming(plan) => {
                let mut out = cli_bulk::render_plan(plan, Mode::Preview);
                out.push('\n');
                out.push_str(&self.footer());
                out
            }
            BulkState::Done(_, text) | BulkState::Refused(text) => text.clone(),
            BulkState::NeedsInput(what) => format!("{what}\n\n{}", self.footer()),
        }
    }
}

/// Render the modal. Never asserts on pixels — a test reads the buffer.
pub fn render(frame: &mut Frame, area: Rect, modal: &BulkModal) {
    let rect = crate::ui::modal::modal_rect(area);
    frame.render_widget(Clear, rect);
    let block = Block::default()
        .borders(Borders::ALL)
        .title(format!(" batch {} ", modal.action.as_str()))
        .border_style(Style::default().fg(ratatui::style::Color::Cyan));
    let inner = block.inner(rect);
    frame.render_widget(block, rect);

    let chunks = Layout::default()
        .direction(Direction::Vertical)
        .constraints([Constraint::Length(3), Constraint::Min(1)])
        .split(inner);
    let header = format!("{}  [{}]", modal.selection.summary(), modal.state_label());
    frame.render_widget(
        Paragraph::new(Line::from(Span::styled(
            header,
            Style::default().add_modifier(Modifier::BOLD),
        ))),
        chunks[0],
    );
    frame.render_widget(
        Paragraph::new(modal.body()).block(Block::default().borders(Borders::TOP)),
        chunks[1],
    );
}

/// The issues a board shows, as `(number, Issue)`, in the order the cards are drawn.
///
/// A function over the board rather than a `store.list()`, because "visible" is the
/// whole point: with a filter applied, `store.list()` returns issues the user cannot
/// see, and marking those would produce a plan for cards that are not on screen.
pub fn visible_issues(
    board: &crate::ui::board::BoardState,
    store: &Store,
) -> Result<Vec<(u32, crate::model::Issue)>> {
    let mut out = Vec::new();
    let mut numbers = Vec::new();
    for index in 0..=board.columns.len() {
        for card in board.column_cards(index) {
            numbers.push(card.number);
        }
    }
    for issue in store.list()? {
        if numbers.contains(&issue.number) {
            out.push((issue.number, issue));
        }
    }
    // Board order, not store order: the plan reads in the order the cards do.
    Ok(numbers
        .into_iter()
        .filter_map(|number| {
            out.iter()
                .find(|(n, _)| *n == number)
                .map(|(n, issue)| (*n, issue.clone()))
        })
        .collect())
}

/// The selection as a list, for the board's own "N selected" popover.
pub fn selection_items(
    selection: &BulkSelection,
    issues: &[(u32, crate::model::Issue)],
) -> Vec<ListItem<'static>> {
    selection
        .numbers()
        .iter()
        .map(|number| {
            let title = issues
                .iter()
                .find(|(n, _)| n == number)
                .map(|(_, i)| i.title.clone())
                .unwrap_or_else(|| "(not on the board)".to_string());
            ListItem::new(format!("#{number} {title}"))
        })
        .collect()
}

/// Render the selection list, for a caller that wants it on screen.
pub fn render_selection_list(
    frame: &mut Frame,
    area: Rect,
    selection: &BulkSelection,
    issues: &[(u32, crate::model::Issue)],
) {
    let list = List::new(selection_items(selection, issues)).block(
        Block::default()
            .borders(Borders::ALL)
            .title(" batch selection "),
    );
    frame.render_widget(list, area);
}