cuj-tui 0.1.0

//! Application state and the command reducer. The reducer is pure
//! state manipulation (it may read the vault and run index
//! queries) and never touches the terminal, so every transition is
//! testable headless.

use std::collections::HashMap;

use metatheca::Uuid;
use ratatui::widgets::ListState;

use crate::cmdline::{CmdLine, ExCommand};
use crate::highlight::{self, Rendered};
use crate::keymap::Command;
use crate::query::{self, FindSpec, SearchEngine};
use crate::snapshot::{JotRow, Snapshot};

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Mode {
    Normal,
    Command,
    Help,
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Focus {
    List,
    View,
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Level {
    Info,
    Warn,
    Error,
}

/// What the left list is currently showing.
pub enum ListSource {
    All,
    Find {
        spec: String,
        entries: Vec<Uuid>,
    },
    Search {
        query: String,
        hits: Vec<(Uuid, f64)>,
        engine: SearchEngine,
        /// The result cap this search ran with (`m` doubles it).
        k: usize,
    },
    Backlinks {
        of_ref: String,
        entries: Vec<Uuid>,
    },
}

impl ListSource {
    pub fn is_all(&self) -> bool {
        matches!(self, ListSource::All)
    }

    /// The list panel's block title.
    pub fn title(&self, count: usize, scope: Option<&str>) -> String {
        match self {
            ListSource::All => {
                format!(" jots — {} ({count}) ", scope.unwrap_or("all"))
            }
            ListSource::Find { spec, .. } => format!(" find: {spec} ({count}) "),
            ListSource::Search { query, engine, .. } => match engine {
                SearchEngine::Hybrid => format!(" search: {query} ({count}) "),
                SearchEngine::Bm25 => format!(" search (bm25): {query} ({count}) "),
            },
            ListSource::Backlinks { of_ref, .. } => {
                format!(" backlinks: {of_ref} ({count}) ")
            }
        }
    }

    /// Score column for search results.
    pub fn score_of(&self, entry: Uuid) -> Option<f64> {
        match self {
            ListSource::Search { hits, .. } => {
                hits.iter().find(|(e, _)| *e == entry).map(|(_, s)| *s)
            }
            _ => None,
        }
    }
}

pub struct AppState {
    pub app: cuj::App,
    pub snapshot: Snapshot,
    /// Profile scope; None = all profiles.
    pub profile: Option<String>,
    pub source: ListSource,
    /// Indices into snapshot.rows: current source ∩ profile scope.
    pub visible: Vec<usize>,
    pub list: ListState,
    pub focus: Focus,
    pub mode: Mode,
    pub view_scroll: u16,
    /// Pre-wrap line count of the selected jot's content.
    pub content_lines: usize,
    pub content_cache: HashMap<Uuid, Rendered>,
    pub cmdline: CmdLine,
    /// Transclusion in the content view (`x` toggles): expanded
    /// content comes from cuj's show --expand path.
    pub expand: bool,
    pub message: Option<(Level, String)>,
    /// The stale-index warning fires once per snapshot.
    pub stale_warned: bool,
    pub quit: bool,
    /// Viewport heights, updated by the draw pass.
    pub list_height: u16,
    pub view_height: u16,
}

impl AppState {
    pub fn new(app: cuj::App) -> crate::Result<AppState> {
        let snapshot = Snapshot::build(&app)?;
        let active = app.client.active_profile.clone();
        let profile = snapshot
            .profiles
            .iter()
            .any(|(name, _)| *name == active)
            .then_some(active);
        let mut state = AppState {
            app,
            snapshot,
            profile,
            source: ListSource::All,
            visible: Vec::new(),
            list: ListState::default(),
            focus: Focus::List,
            mode: Mode::Normal,
            view_scroll: 0,
            content_lines: 0,
            content_cache: HashMap::new(),
            cmdline: CmdLine::default(),
            expand: false,
            message: None,
            stale_warned: false,
            quit: false,
            list_height: 0,
            view_height: 0,
        };
        state.recompute_visible();
        Ok(state)
    }

    pub fn scope(&self) -> Option<&str> {
        self.profile.as_deref()
    }

    /// Rebuild `visible` from source ∩ scope and clamp selection.
    pub fn recompute_visible(&mut self) {
        let scope = self.profile.clone();
        let scope = scope.as_deref();
        let snap = &self.snapshot;
        let in_scope = |i: &usize| scope.is_none_or(|p| snap.rows[*i].profile == p);
        self.visible = match &self.source {
            ListSource::All => (0..snap.rows.len()).filter(in_scope).collect(),
            ListSource::Find { entries, .. } | ListSource::Backlinks { entries, .. } => entries
                .iter()
                .filter_map(|e| snap.by_entry.get(e).copied())
                .filter(in_scope)
                .collect(),
            ListSource::Search { hits, .. } => hits
                .iter()
                .filter_map(|(e, _)| snap.by_entry.get(e).copied())
                .filter(in_scope)
                .collect(),
        };
        match (self.list.selected(), self.visible.len()) {
            (_, 0) => self.list.select(None),
            (None, _) => self.select_index(0),
            (Some(s), n) if s >= n => self.select_index(n - 1),
            _ => {}
        }
    }

    pub fn selected_row(&self) -> Option<&JotRow> {
        let i = self.list.selected()?;
        self.visible.get(i).map(|&r| &self.snapshot.rows[r])
    }

    /// Select by position in `visible`, resetting the view scroll.
    pub fn select_index(&mut self, i: usize) {
        if self.visible.is_empty() {
            self.list.select(None);
            return;
        }
        let i = i.min(self.visible.len() - 1);
        if self.list.selected() != Some(i) {
            self.view_scroll = 0;
        }
        self.list.select(Some(i));
    }

    /// Select the row holding `entry`, if visible.
    pub fn select_entry(&mut self, entry: Uuid) -> bool {
        let pos = self
            .visible
            .iter()
            .position(|&r| self.snapshot.rows[r].entry == entry);
        match pos {
            Some(i) => {
                self.select_index(i);
                true
            }
            None => false,
        }
    }

    pub fn set_message(&mut self, level: Level, text: impl Into<String>) {
        self.message = Some((level, text.into()));
    }

    /// Load the selected jot's content into the cache (head-only,
    /// so `Vault::get_bytes` suffices — no transient Reads needed),
    /// highlighted under its profile's parser configuration, and
    /// clamp the view scroll. Called once per loop iteration,
    /// before drawing.
    pub fn ensure_content(&mut self) {
        let Some((entry, profile, id)) = self
            .selected_row()
            .map(|r| (r.entry, r.profile.clone(), r.id))
        else {
            self.content_lines = 0;
            self.view_scroll = 0;
            return;
        };
        if !self.content_cache.contains_key(&entry) {
            let raw = || match self.app.vault.get_bytes(&entry.hyphenated().to_string()) {
                Ok(b) => String::from_utf8_lossy(&b).into_owned(),
                Err(e) => format!("(content unavailable: {e})"),
            };
            // Transclusion goes through cuj's expanding show path;
            // plain view reads the blob directly.
            let text = if self.expand {
                let r = cuj::RefArg {
                    profile: Some(profile.clone()),
                    id,
                    suffix: None,
                };
                match cuj::queries::show(&self.app, &cuj::Opts::default(), &r, true) {
                    Ok(cuj::queries::ShowOutcome::Shown { content, .. }) => content,
                    _ => raw(),
                }
            } else {
                raw()
            };
            let config = self
                .snapshot
                .configs
                .get(&profile)
                .cloned()
                .unwrap_or_else(|| cuj::facts::ProfileConfig::new(&profile));
            self.content_cache
                .insert(entry, highlight::render(&text, &config));
        }
        self.content_lines = self.content_cache[&entry].lines.len();
        // Approximate clamp: scroll offsets are pre-wrap lines.
        let max = self
            .content_lines
            .saturating_sub(self.view_height.max(1) as usize)
            .min(u16::MAX as usize) as u16;
        if self.view_scroll > max {
            self.view_scroll = max;
        }
    }

    pub fn content_of(&self, entry: Uuid) -> Option<&Rendered> {
        self.content_cache.get(&entry)
    }
}

// ── the reducer ────────────────────────────────────────────────────

pub fn apply(state: &mut AppState, cmd: Command) {
    // Any new command clears the previous message.
    state.message = None;
    match cmd {
        Command::Quit => state.quit = true,
        Command::Help => state.mode = Mode::Help,
        Command::Reload => reload(state),
        Command::CycleFocus => {
            state.focus = match state.focus {
                Focus::List => Focus::View,
                Focus::View => Focus::List,
            };
        }
        Command::Open => {
            if state.list.selected().is_some() {
                state.focus = Focus::View;
            }
        }
        Command::Back => back(state),
        Command::MoveDown => move_by(state, 1),
        Command::MoveUp => move_by(state, -1),
        Command::MoveTop => move_top(state),
        Command::MoveBottom => move_bottom(state),
        Command::HalfPageDown => move_by(state, half_page(state)),
        Command::HalfPageUp => move_by(state, -half_page(state)),
        Command::NextProfile => next_profile(state),
        Command::StartCommand(prefill) => {
            state.mode = Mode::Command;
            state.cmdline.start(prefill);
        }
        Command::Backlinks => backlinks_selected(state),
        Command::MoreResults => more_results(state),
        Command::ToggleExpand => {
            state.expand = !state.expand;
            state.content_cache.clear();
            state.set_message(
                Level::Info,
                if state.expand {
                    "transclusion on"
                } else {
                    "transclusion off"
                },
            );
        }
        // Edit needs the terminal (suspend, $EDITOR, resume), so
        // the run loop intercepts it before the reducer; reaching
        // here means a context without a terminal.
        Command::Edit => state.set_message(Level::Error, "edit needs a terminal"),
        Command::Ex(ex) => apply_ex(state, ex),
    }
}

fn more_results(state: &mut AppState) {
    match &state.source {
        ListSource::Search { query, k, .. } => {
            let (query, k) = (query.clone(), k.saturating_mul(2));
            run_search_k(state, query, k);
        }
        _ => state.set_message(Level::Info, "more applies to search results"),
    }
}

/// The selected jot as an edit target: an explicit-profile RefArg
/// plus its display label.
pub fn edit_target(state: &AppState) -> Option<(cuj::RefArg, String)> {
    let row = state.selected_row()?;
    let r = cuj::RefArg {
        profile: Some(row.profile.clone()),
        id: row.id,
        suffix: None,
    };
    Some((r, format!("--{}--{}", row.profile, row.id)))
}

fn apply_ex(state: &mut AppState, ex: ExCommand) {
    match ex {
        ExCommand::Quit => state.quit = true,
        ExCommand::Help => state.mode = Mode::Help,
        ExCommand::Reload => reload(state),
        ExCommand::Profile(name) => set_profile(state, name),
        ExCommand::Find(spec) => run_find(state, spec),
        ExCommand::Search(query) => run_search(state, query),
        ExCommand::Goto(r) => goto(state, &r),
        ExCommand::Backlinks(Some(r)) => match resolve_ref(state, &r) {
            Ok(i) => {
                let row = &state.snapshot.rows[i];
                let (entry, label) = (row.entry, row.short_ref(state.scope()));
                run_backlinks(state, entry, label);
            }
            Err(msg) => state.set_message(Level::Error, msg),
        },
        ExCommand::Backlinks(None) => backlinks_selected(state),
    }
}

// ── movement ───────────────────────────────────────────────────────

fn half_page(state: &AppState) -> i64 {
    let h = match state.focus {
        Focus::List => state.list_height,
        Focus::View => state.view_height,
    };
    (h / 2).max(1) as i64
}

fn move_by(state: &mut AppState, delta: i64) {
    match state.focus {
        Focus::List => {
            let Some(sel) = state.list.selected() else {
                return;
            };
            let n = state.visible.len() as i64;
            let next = (sel as i64 + delta).clamp(0, (n - 1).max(0));
            state.select_index(next as usize);
        }
        Focus::View => {
            let next = (state.view_scroll as i64 + delta).max(0);
            // Upper clamp happens in ensure_content, which knows
            // the content length.
            state.view_scroll = next.min(u16::MAX as i64) as u16;
        }
    }
}

fn move_top(state: &mut AppState) {
    match state.focus {
        Focus::List => state.select_index(0),
        Focus::View => state.view_scroll = 0,
    }
}

fn move_bottom(state: &mut AppState) {
    match state.focus {
        Focus::List => {
            if !state.visible.is_empty() {
                state.select_index(state.visible.len() - 1);
            }
        }
        // Clamped down to the real maximum by ensure_content.
        Focus::View => state.view_scroll = u16::MAX,
    }
}

/// Staged retreat: View → List, then results → all jots.
fn back(state: &mut AppState) {
    if state.focus == Focus::View {
        state.focus = Focus::List;
        return;
    }
    if !state.source.is_all() {
        let keep = state.selected_row().map(|r| r.entry);
        state.source = ListSource::All;
        state.recompute_visible();
        if let Some(e) = keep {
            state.select_entry(e);
        }
    }
}

// ── profile scope ──────────────────────────────────────────────────

fn next_profile(state: &mut AppState) {
    let mut options: Vec<Option<String>> = state
        .snapshot
        .profiles
        .iter()
        .map(|(name, _)| Some(name.clone()))
        .collect();
    options.push(None);
    let cur = options
        .iter()
        .position(|o| *o == state.profile)
        .unwrap_or(options.len() - 1);
    let next = options[(cur + 1) % options.len()].clone();
    set_scope(state, next);
}

fn set_profile(state: &mut AppState, name: String) {
    if name == "all" {
        set_scope(state, None);
    } else if state.snapshot.profiles.iter().any(|(n, _)| *n == name) {
        set_scope(state, Some(name));
    } else {
        state.set_message(Level::Error, format!("not found: profile {name:?}"));
    }
}

fn set_scope(state: &mut AppState, scope: Option<String>) {
    state.profile = scope;
    state.recompute_visible();
    state.select_index(0);
    let label = match state.scope() {
        Some(p) => format!("profile: {p} ({} jots)", state.visible.len()),
        None => format!("profile: all ({} jots)", state.visible.len()),
    };
    state.set_message(Level::Info, label);
}

// ── snapshot reload ────────────────────────────────────────────────

fn reload(state: &mut AppState) {
    let keep = state.selected_row().map(|r| r.entry);
    match Snapshot::build(&state.app) {
        Ok(s) => {
            state.snapshot = s;
            state.content_cache.clear();
            state.stale_warned = false;
            if let Some(p) = state.profile.clone() {
                if !state.snapshot.profiles.iter().any(|(n, _)| *n == p) {
                    state.profile = None;
                }
            }
            state.recompute_visible();
            if let Some(e) = keep {
                state.select_entry(e);
            }
            state.set_message(Level::Info, "reloaded");
        }
        Err(e) => state.set_message(Level::Error, e.to_string()),
    }
}

// ── queries ────────────────────────────────────────────────────────

fn run_find(state: &mut AppState, spec: FindSpec) {
    match query::find(&state.app, &spec) {
        Ok((entries, stale)) => {
            state.source = ListSource::Find {
                spec: spec.raw.clone(),
                entries,
            };
            finish_query(state, stale, None);
        }
        Err(e) => state.set_message(Level::Error, e.to_string()),
    }
}

fn run_search(state: &mut AppState, query_text: String) {
    run_search_k(state, query_text, 50);
}

fn run_search_k(state: &mut AppState, query_text: String, k: usize) {
    match query::search(&state.app, &state.snapshot, &query_text, k) {
        Ok((hits, stale, engine)) => {
            state.source = ListSource::Search {
                query: query_text,
                hits,
                engine,
                k,
            };
            let note = match engine {
                SearchEngine::Hybrid => None,
                SearchEngine::Bm25 => Some(" — bm25 only (no zetetes chain; run 'zetetes init')"),
            };
            finish_query(state, stale, note);
        }
        Err(e) => state.set_message(Level::Error, e.to_string()),
    }
}

fn backlinks_selected(state: &mut AppState) {
    let Some(row) = state.selected_row() else {
        state.set_message(Level::Error, "no jot selected");
        return;
    };
    let (entry, label) = (row.entry, row.short_ref(state.scope()));
    run_backlinks(state, entry, label);
}

fn run_backlinks(state: &mut AppState, of: Uuid, label: String) {
    match query::backlinks(&state.app, of) {
        Ok((entries, stale)) => {
            state.source = ListSource::Backlinks {
                of_ref: label,
                entries,
            };
            finish_query(state, stale, None);
        }
        Err(e) => state.set_message(Level::Error, e.to_string()),
    }
}

fn finish_query(state: &mut AppState, stale: bool, note: Option<&str>) {
    state.recompute_visible();
    state.select_index(0);
    state.focus = Focus::List;
    if stale && !state.stale_warned {
        state.stale_warned = true;
        state.set_message(
            Level::Warn,
            "index stale — results may lag; run 'cuj reindex'",
        );
    } else {
        let n = state.visible.len();
        state.set_message(
            Level::Info,
            format!("{n} result{}{}", plural(n), note.unwrap_or("")),
        );
    }
}

fn plural(n: usize) -> &'static str {
    if n == 1 { "" } else { "s" }
}

// ── goto ───────────────────────────────────────────────────────────

/// Resolve a `--ref` against the snapshot: explicit profile, else
/// the scoped profile (bare `--N` is ambiguous under `all`, as in
/// the CLI).
fn resolve_ref(state: &AppState, r: &cuj::RefArg) -> Result<usize, String> {
    let profile = match r.profile.clone().or_else(|| state.profile.clone()) {
        Some(p) => p,
        None => {
            return Err("bare --N is ambiguous under profile all; use --profile--N".into());
        }
    };
    state
        .snapshot
        .by_ident
        .get(&(profile.clone(), r.id))
        .copied()
        .ok_or_else(|| format!("not found: --{profile}--{}", r.id))
}

fn goto(state: &mut AppState, r: &cuj::RefArg) {
    let row_idx = match resolve_ref(state, r) {
        Ok(i) => i,
        Err(msg) => {
            state.set_message(Level::Error, msg);
            return;
        }
    };
    let (entry, profile) = {
        let row = &state.snapshot.rows[row_idx];
        (row.entry, row.profile.clone())
    };
    // Widen scope if the target lives in another profile.
    if state.scope().is_some_and(|p| p != profile) {
        state.profile = Some(profile);
        state.recompute_visible();
    }
    if !state.select_entry(entry) {
        // Not in the current result list: fall back to all jots.
        state.source = ListSource::All;
        state.recompute_visible();
        state.select_entry(entry);
    }
    state.focus = Focus::View;
    // A fragment or bookmark suffix scrolls the view to its line.
    if let Some(suffix) = r.suffix.clone() {
        scroll_to_suffix(state, entry, &suffix);
    }
}

/// The pre-wrap line a reference suffix points at; ensure_content
/// clamps against the real content length afterwards.
fn scroll_to_suffix(state: &mut AppState, entry: Uuid, suffix: &cuj::app::Suffix) {
    let text = match state.app.vault.get_bytes(&entry.hyphenated().to_string()) {
        Ok(b) => String::from_utf8_lossy(&b).into_owned(),
        Err(_) => return,
    };
    let line = match suffix {
        cuj::app::Suffix::Lines(a, _) => a.saturating_sub(1),
        cuj::app::Suffix::Bookmark(name) => {
            let anchor = format!("!!{name}");
            match text
                .lines()
                .position(|l| l.split_whitespace().any(|w| w == anchor))
            {
                Some(i) => i,
                None => {
                    state.set_message(Level::Warn, format!("bookmark #{name} not found"));
                    return;
                }
            }
        }
    };
    state.view_scroll = line.min(u16::MAX as usize) as u16;
}