//! The builtins: one struct each, plus setting commands generated from one
//! runtime_config table.
//!
//! Executing a builtin's NAME (middle-click / Tab) runs it through the one
//! dispatcher (Pardes.runBuiltin), no matter where the name appears. The
//! struct's DECL NAME is the user-visible word — the one in the topbar, the
//! one sitting in a tag, the one Help prints, the one you execute — so
//! `std.meta.stringToEnum` is the lookup and there is no name table to sync.
//!
//! A zig file IS a struct, so THIS FILE'S declarations are the manual list:
//! the registry walks them at comptime and appends the enabled settings from
//! runtime_config.settings. There is no hand-maintained enum or dispatcher
//! switch to keep in sync; declarations and setting descriptors are the data.
//!
//! A manual builtin is a struct declaring `pub fn run(Ctx) void`; an optional
//! explicit `enabled` declaration gates it. Helpers have no `run`, and a
//! claimed builtin with the wrong signature is a compile error.
//!
//! What is NOT here: the key bindings. `leader_path` is ONE table in
//! config.zig next to `topbar_str` and every other syntactic choice — the
//! whole remapping surface belongs in one file a user can read top to bottom,
//! not scattered a line at a time across thirty-three structs.
const std = @import("std");
const pardes = @import("pardes.zig");
const Pardes = pardes.Pardes;
const Pane = pardes.Pane;
const output_pane = @import("output_pane.zig");
const image_pane = @import("image_pane.zig");
const config = @import("config.zig");
const runtime_config = @import("runtime_config.zig");
const board_memory = @import("board_memory.zig");

/// The platform's runtime-setting facilities, stated once as plain data.
/// Registry generation, leader paths, Config, and EffectCode all consume this
/// exact value rather than rebuilding equivalent-looking boolean expressions.
pub const capabilities: runtime_config.Capabilities = .{
    .font_picker = pardes.font_picker,
    // A transition is composited by the shell, and EffectCode has to be able
    // to show WHICH compositor: only the three hosted shells are in this
    // package, so the hostless platforms have no honest source to print.
    .panel_transitions = pardes.hosted,
    .scene_shaders = pardes.platform == .gui or pardes.platform == .macos,
    // The tty's font belongs to its emulator, and the P4 firmware's belongs to
    // whatever terminal is on the other end of the serial line.
    .tagline_font_size = pardes.platform != .tty and pardes.platform != .p4,
};

/// What a builtin gets to act on. One bundle rather than five parameters
/// because most builtins want two of them and zig rejects the unused rest.
/// `txt` is the executed text (Restore reads its path back out of it) and
/// `arg` the execute's ARGUMENT — text typed after the name, or the selection
/// a mouse chord kept, which is why Grep and Find run straight away when there
/// is one instead of asking. The leader passes "" and null: a key path names a
/// builtin, never an argument.
pub const Ctx = struct {
    p: *Pardes,
    /// pane `id`, already resolved — the dispatcher's null check is the one
    /// guard every builtin used to share.
    pane: *Pane,
    id: usize,
    txt: []const u8,
    arg: ?[]const u8,
};

/// Every enabled builtin, in source order. Feature gates are explicit data;
/// a declaration that claims to be enabled but has the wrong run signature is
/// a compile error instead of silently disappearing from the command enum.
fn isEnabled(comptime T: type) bool {
    return !@hasDecl(T, "enabled") or T.enabled;
}

fn manualBuiltinCount() comptime_int {
    comptime {
        var count = 0;
        for (@typeInfo(@This()).@"struct".decls) |d| {
            if (@TypeOf(@field(@This(), d.name)) != type) continue;
            const T = @field(@This(), d.name);
            if (@typeInfo(T) != .@"struct" or !@hasDecl(T, "run") or !isEnabled(T)) continue;
            if (@TypeOf(T.run) != fn (Ctx) void)
                @compileError(d.name ++ ".run must have signature fn (Ctx) void");
            count += 1;
        }
        return count;
    }
}

fn manualBuiltinList() [manualBuiltinCount()]type {
    comptime {
        @setEvalBranchQuota(4000);
        var list: [manualBuiltinCount()]type = undefined;
        var count = 0;
        for (@typeInfo(@This()).@"struct".decls) |d| {
            if (@TypeOf(@field(@This(), d.name)) != type) continue;
            const T = @field(@This(), d.name);
            if (@typeInfo(T) != .@"struct" or !@hasDecl(T, "run") or !isEnabled(T)) continue;
            list[count] = T;
            count += 1;
        }
        return list;
    }
}

fn settingCount() comptime_int {
    comptime {
        var count = 0;
        for (runtime_config.settings) |setting| if (setting.enabled(capabilities)) {
            count += 1;
        };
        return count;
    }
}

fn settingList() [settingCount()]runtime_config.Setting {
    comptime {
        var list: [settingCount()]runtime_config.Setting = undefined;
        var count = 0;
        for (runtime_config.settings) |setting| if (setting.enabled(capabilities)) {
            list[count] = setting;
            count += 1;
        };
        return list;
    }
}

/// A builtin's user-visible word: the LAST dotted segment of `@typeName`,
/// because @typeName spells a file-scope struct fully qualified
/// ("builtins.Kill"). Deriving it beats a `pub const name` field per struct,
/// which would be the same word written twice with nothing keeping the two
/// honest. A name that is not a legal identifier would be spelled `@"..."`.
pub fn word(comptime T: type) []const u8 {
    const n = @typeName(T);
    const dot = std.mem.lastIndexOfScalar(u8, n, '.') orelse return n;
    return n[dot + 1 ..];
}

pub const OutputTraits = struct {
    name: []const u8,
    steps: bool = false,
    jumps: bool = false,
    commands: bool = false,
    doc: bool = false,
    /// the buffer BECOMES an ordinary file once written (the New scratch, and a
    /// real file, which is one already). Every other output buffer is a
    /// RENDERING: Save writes its text out and the buffer stays what it is,
    /// refillable and steppable, because a saved copy of a search is a copy of
    /// a search and not the search.
    saves: bool = false,
};

/// The enum: field name = struct name, value = index into `all()`. Everything
/// downstream (leader_path's EnumArray, leader_rows, the topbar's comptime
/// check, stringToEnum) speaks it exactly as it did when it was hand-written.
///
/// Registry-dependent APIs live in one namespace so the outer declaration
/// walk only sees this namespace's type, not functions whose signatures depend
/// on the builtin enum being constructed.
pub const registry = struct {
    pub fn Builtin() type {
        // The duplicate-name check below is O(n^2) string comparisons over every manual builtin AND
        // every generated setting, so this quota grows quadratically with the builtin count. 20,000
        // was enough until three more (Peek/Poke/Hexdump) tipped `-Dplatform=gui` over with
        // "evaluation exceeded 20000 backwards branches". Raised with room rather than to the next
        // value that happens to pass, so the next builtin does not have to rediscover this.
        @setEvalBranchQuota(200_000);
        const manual = manualBuiltinList();
        const generated = settingList();
        const count = manual.len + generated.len;
        const Tag = std.math.IntFittingRange(0, count - 1);
        var names: [count][]const u8 = undefined;
        for (manual, 0..) |T, i| names[i] = word(T);
        for (generated, manual.len..) |setting, i| names[i] = setting.word;
        for (names, 0..) |name, i| for (names[i + 1 ..]) |later|
            if (std.mem.eql(u8, name, later)) @compileError("duplicate builtin name: " ++ name);
        return @Enum(Tag, .exhaustive, &names, &std.simd.iota(Tag, count));
    }

    pub fn takesArg(b: Builtin()) bool {
        inline for (manualBuiltinList(), 0..) |T, i|
            if (@intFromEnum(b) == i) return @hasDecl(T, "takes_arg") and T.takes_arg;
        inline for (comptime settingList(), manualBuiltinCount()..) |setting, i|
            if (@intFromEnum(b) == i) return setting.takesArg();
        unreachable;
    }

    pub fn outputTraits(b: Builtin()) ?OutputTraits {
        inline for (manualBuiltinList(), 0..) |T, i|
            if (@intFromEnum(b) == i) return if (@hasDecl(T, "output")) T.output else null;
        inline for (comptime settingList(), manualBuiltinCount()..) |_, i|
            if (@intFromEnum(b) == i) return null;
        unreachable;
    }

    pub fn dispatch(b: Builtin(), c: Ctx) void {
        inline for (manualBuiltinList(), 0..) |T, i|
            if (@intFromEnum(b) == i) return T.run(c);
        inline for (comptime settingList(), manualBuiltinCount()..) |setting, i|
            if (@intFromEnum(b) == i) return c.p.applySettingBuiltin(setting, c.arg);
        unreachable;
    }
};

test "capabilities exactly gate setting and effect-source builtins" {
    const Builtin = registry.Builtin();
    for (runtime_config.settings) |setting| {
        const registered = std.meta.stringToEnum(Builtin, setting.word) != null;
        try std.testing.expectEqual(setting.enabled(capabilities), registered);
    }
    const effect_code_registered = std.meta.stringToEnum(Builtin, "EffectCode") != null;
    try std.testing.expectEqual(EffectCode.enabled, effect_code_registered);
}

// The three memory words, checked the same way but at COMPTIME rather than in
// a test, because the property is about builds this test binary is not: the
// tty suite can only ever observe its own platform, and what matters is that
// `-Dplatform=web -Dtarget=wasm32-freestanding` does not quietly hand a
// browser tab a Poke. Every build of every platform now proves its own half.
comptime {
    for ([_][]const u8{ "Peek", "Poke", "Hexdump" }) |name|
        if (@hasField(registry.Builtin(), name) != board_memory.enabled) @compileError(
            "bare-metal memory word gating leaked: " ++ name,
        );
}

// ---- the two acme verbs ----

// Look and Execute are the verbs the whole environment is built on, and they
// are BUILTINS: `Look main.zig` typed in a tag and executed is the same look a
// right click on `main.zig` is, `Exec ls` the same as a middle click on `ls`.
// The mouse buttons and Enter/Tab are not a second path into them any more —
// they are two bindings pointing here (config.look_cmd / exec_cmd), the status
// `SPC f s` has relative to Save. That is the whole feature: what used to be a
// `button` parameter threaded through every keyboard call site, with the
// builtin dispatch nested INSIDE it, is now one word each.
//
// The operand is `arg` in both — a name's tail (`Look main.zig`), else the
// selection a chord kept, else the word the gesture pointed at, which the
// gesture resolves and passes. Nothing to act on means nothing happens, the
// way `Save` on a terminal is inert.

pub const Look = struct {
    pub const takes_arg = true;
    pub fn run(c: Ctx) void {
        c.p.lookAt(c.id, c.arg orelse return);
    }
};

pub const Exec = struct {
    pub const takes_arg = true;
    pub fn run(c: Ctx) void {
        // the destination pane is Look's business (it focuses what answered);
        // an execute deliberately leaves you where you were
        _ = c.p.execute(c.id, c.arg orelse return);
    }
};

// ---- session ----

pub const Kill = struct {
    pub fn run(c: Ctx) void {
        c.p.quit = true;
        c.p.emit(.quit);
    }
};

pub const Dump = struct {
    pub fn run(c: Ctx) void {
        c.p.dumpState() catch {};
    }
};

pub const Restore = struct {
    pub const takes_arg = true;
    pub fn run(c: Ctx) void {
        var it = std.mem.tokenizeAny(u8, c.txt, " \t");
        _ = it.next(); // the word "Restore"
        const path = it.next() orelse (c.p.last_dump orelse return);
        if (path.len > c.p.restore_buf.len) return;
        @memcpy(c.p.restore_buf[0..path.len], path);
        c.p.restore_req = c.p.restore_buf[0..path.len];
    }
};

// ---- the message row ----

/// TEXT onto this pane's transient message row — the row a failed save, a
/// refused Look and a language server that would not start all report through
/// (Pardes.setMessage, and Pardes.reportError one line above it). Every writer
/// of that row is something going wrong, so until this word there was no way
/// to look at it without breaking something on purpose: no wording could be
/// checked against a narrow pane, and no test could pin the row without
/// arranging a real failure first.
///
/// Bare, it reports ITSELF through the error path, because that is the other
/// half of the same machinery — `reportError` is `setMessage` plus an
/// `<operation>: <Error>` — and because a word that needs no argument to
/// demonstrate one is a word you can also just click.
///
/// Whether the row is FREE is not asked here and is not this word's business:
/// an armed prompt outranks a message at render time, so posting under one is
/// stored and invisible, exactly as a save finishing under one is. Nor does
/// anything here decide when it goes away — your next key or click does, on
/// every pane at once, because a message is exactly as old as your last input.
pub const Msg = struct {
    pub const takes_arg = true;
    pub fn run(c: Ctx) void {
        if (c.arg) |text|
            c.p.setMessage(c.id, text)
        else
            c.p.reportError(c.id, comptime word(@This()), error.NoMessage);
    }
};

// ---- display choices ----
//
// The plain toggles, named theme/shell/font setters and animation effects are
// generated from runtime_config.settings. Keeping their command metadata and
// their query order in the same value table is what prevents a settable choice
// from disappearing from Config. Hand-written commands continue below.

/// One step along the ring. With 228 themes in it this is no longer a way to
/// REACH a theme — ThemeSel is — but it is still the way to browse one, and the
/// browse got better rather than worse: the generated half is sorted by name, so
/// the neighbours of wherever you are are that theme's own variants (light,
/// hard, soft, the whole gruvbox family in a row). Kept as the topbar word and
/// SPC t n it has always been; a ring you can walk off the end of in three
/// clicks was never what made it useful.
pub const NextColor = struct {
    pub fn run(c: Ctx) void {
        c.p.setThemeIndex((@as(usize, c.p.settings.theme) + 1) % pardes.themes.len);
    }
};

/// The theme BY NAME — `Theme acme`. The ring grew past the point where
/// cycling to the one you want is reasonable, so this is the way to ask for
/// one, and NextColor stays as the way to browse. Inert without an argument
/// (there is no theme called nothing), which is also why it has no leader path:
/// a key path names a builtin and can never carry the name of a theme.
///
/// A LINEAR SCAN over 228 names, on a keystroke: the alternative is a comptime
/// name->index map, which is a second copy of the ring to build for a lookup
/// nobody will ever measure. 228 short string compares is microseconds, and it
/// happens once per theme change, not once per frame.
/// ...and the list of what Theme takes, as a buffer you walk. Its rows are
/// `Theme <name>` COMMANDS rather than locations, which is one flag on the
/// buffer (output_pane.Traits.commands) and changes what a step SELECTS: the
/// whole line, since there is no path inside it to pick out. Tab on what n
/// selected wears that theme — the same middle click on the row is — so
/// walking the list with n/Tab is trying them on, and stopping is choosing.
pub const ThemeSel = struct {
    pub const output: OutputTraits = .{ .name = config.themes_buffer, .steps = true, .commands = true };
    pub fn run(c: Ctx) void {
        output_pane.openThemes(c.p, c.id) catch |err| c.p.reportError(c.id, "themes", err);
    }
};

/// Load one complete Theme value from a .zon file. Relative paths are rooted
/// at the per-user pardes directory, so an init line can simply say
/// `ThemeFile themes/mine.zon`. The native host owns the read and watch; the
/// core owns parsing and keeps the last valid value across a bad live edit.
pub const ThemeFile = struct {
    pub const takes_arg = true;
    pub const enabled = pardes.hosted;
    pub fn run(c: Ctx) void {
        if (comptime enabled)
            c.p.requestThemeFile(c.id, c.arg orelse return)
        else
            unreachable;
    }
};

/// Materialize every compiled theme as editable ZON under
/// `<config>/themes/builtin`. Filesystem work remains a host effect, just like
/// Dump and Save; the build-time ring itself is the sole source of the data.
pub const DumpThemes = struct {
    pub const enabled = pardes.hosted;
    pub fn run(c: Ctx) void {
        if (comptime enabled) {
            if (c.p.opts.config_dir == null) {
                c.p.reportError(c.id, "dump themes", error.NoConfigDirectory);
                return;
            }
            c.p.emit(.{ .dump_themes = .{ .pane = @intCast(c.id) } });
        } else unreachable;
    }
};

// ---- the GUI's font list, and NOTHING on any other platform ----
//
// Runtime settings such as Font are generated from runtime_config.settings.
// FontSel remains hand-written because it opens a result pane. Its explicit
// `enabled` bit is the same feature gate the registry uses for PDF commands:
// disabled commands have no enum field, help row, or dispatcher case.

/// The GUI font BY NAME — `Font DejaVuSansMono-Regular`, the way `Theme <name>`
/// takes a theme, and inert without an argument for the same reason (there is
/// no font called nothing). The name is a font FILE's stem, which is what the
/// picker lists; resolving it is a walk of the font directories that stops at
/// the first match, so nothing is cached and an install five seconds ago is
/// findable.
///
/// The core cannot load a font — it has no rasterizer, no atlas and no window
/// — so this asks: the resolved PATH goes in runtime config, the shell takes it on
/// its next pass and re-rasters. Exactly the shape Restore already has.
/// ...and the list of what Font takes: every MONOSPACE font on the machine,
/// one `Font <name>` row each, in the picker ThemeSel already is (rows that
/// are commands, so n/N select each one WHOLE and Tab runs it — walking with
/// n and pressing Tab wears each font in turn, and picking one is stopping
/// there).
///
/// Monospace only, which is the one judgement in the feature: the grid is a
/// fixed cell, so a proportional face is not a worse-looking option but an
/// unreadable one — and this picker EXECUTES what it steps onto, so listing
/// them would mean the list wearing one on the way past. See fonts.monospaced.
pub const FontSel = struct {
    pub const output: OutputTraits = .{ .name = config.fonts_buffer, .steps = true, .commands = true };
    pub const enabled = capabilities.font_picker;
    pub fn run(c: Ctx) void {
        if (comptime enabled) apply(c) else unreachable;
    }
    fn apply(c: Ctx) void {
        output_pane.openFonts(c.p, c.id) catch |err| c.p.reportError(c.id, "fonts", err);
    }
};

/// Toggle a native PDF between the reading-oriented fit-width view and the
/// whole-page-height view. The explicit feature gate omits the command, help
/// row, and dispatcher case when MuPDF is disabled.
pub const PdfFit = struct {
    pub const enabled = pardes.pdf_enabled;
    pub fn run(c: Ctx) void {
        if (comptime enabled) apply(c) else unreachable;
    }
    fn apply(c: Ctx) void {
        pardes.pdf_pane.toggleFit(c.pane);
    }
};

/// Cycle a native PDF through original pixels, a chroma-preserving themed
/// filter, and a full theme duotone. It has the same explicit feature gate as
/// PdfFit: absent without MuPDF and inert off a PDF pane.
pub const PdfTint = struct {
    pub const enabled = pardes.pdf_enabled;
    pub fn run(c: Ctx) void {
        if (comptime enabled) apply(c) else unreachable;
    }
    fn apply(c: Ctx) void {
        pardes.pdf_pane.toggleTint(c.pane);
    }
};

/// Show this PDF's document outline as a live, steppable output pane. The
/// command is absent from non-MuPDF builds and deliberately inert on every
/// other pane kind, like the two PDF display toggles above.
pub const PdfSections = struct {
    pub const output: OutputTraits = .{ .name = config.pdf_sections_buffer, .steps = true };
    pub const enabled = pardes.pdf_enabled;
    pub fn run(c: Ctx) void {
        if (comptime enabled) apply(c) else unreachable;
    }
    fn apply(c: Ctx) void {
        pardes.pdf_pane.openSections(c.p, c.id);
    }
};

// The image pane's three renderer toggles. They used to be executable words
// interpreted by a special tag dispatcher; as ordinary builtins they are
// pressable under SPC and listed by `SPC ?`. The tag now reports their plain
// live values without becoming a second mutation path. Each acts on the pane
// it runs in and is inert elsewhere, the way Save is on a terminal.

/// glyph art over the host's pixels
pub const Petscii = struct {
    pub fn run(c: Ctx) void {
        if (c.pane.image) |*state| image_pane.togglePetscii(state);
    }
};

/// the C64 palette or the terminal's own 16
pub const Palette = struct {
    pub fn run(c: Ctx) void {
        if (c.pane.image) |*state| image_pane.togglePalette(state);
    }
};

/// add the printable ASCII bitmaps to the matcher's glyph set
pub const Ascii = struct {
    pub fn run(c: Ctx) void {
        if (c.pane.image) |*state| image_pane.toggleAscii(state);
    }
};

// ---- the system clipboard ----

// helix's `<space>` clipboard menu, and the ONLY five words in pardes that
// touch the desktop's clipboard. Everything else — `y`, `d`, `c`, `p`, `P`,
// `R`, the acme cut/paste chords — lives entirely in the internal register,
// which is helix's arrangement and, less abstractly, the reason deleting a
// character no longer throws away whatever you had copied from a browser.
//
// They are builtins rather than bare chords because the leader table is the
// remapping surface and a leader path names a builtin: spelling them here
// puts them in Help's index, makes them executable words like every other
// verb, and costs no second mechanism. Their paths ARE helix's letters, on
// the same leader helix uses — see config.leader_path.
//
// The two directions are not symmetric, and cannot be. Writing is a fire-off:
// the core owns the bytes and the shell copies them out. READING has to leave
// the core and come back — SDL and NSPasteboard answer inside the same drain,
// a browser answers a promise later, and a terminal answers over OSC 52 or,
// far more often, refuses outright. So a paste is a REQUEST (the
// read_clipboard effect) that may simply never be answered, and a `SPC p`
// that does nothing in a locked-down terminal is the honest outcome rather
// than a bug to paper over with the internal register.

pub const ClipYank = struct {
    pub fn run(c: Ctx) void {
        c.p.clipYank(c.pane, false);
    }
};

/// helix `<space>Y`: the PRIMARY selection alone, where `SPC y` joins every
/// cursor's. One cursor makes them the same word.
pub const ClipYankMain = struct {
    pub fn run(c: Ctx) void {
        c.p.clipYank(c.pane, true);
    }
};

pub const ClipPaste = struct {
    pub fn run(c: Ctx) void {
        c.p.clipRequest(c.id, .after);
    }
};

pub const ClipPasteBefore = struct {
    pub fn run(c: Ctx) void {
        c.p.clipRequest(c.id, .before);
    }
};

pub const ClipReplace = struct {
    pub fn run(c: Ctx) void {
        c.p.clipRequest(c.id, .replace);
    }
};

// ---- panes and columns ----

/// Write this pane's text out. A pane with a real file behind it writes THAT
/// file with no argument — acme's Put, what `:w<Tab>` has always meant — and
/// that is the only pane Save can serve without being told where.
///
/// Everywhere else the path is REQUIRED, so a bare `Save` asks for one exactly
/// the way Find and Grep ask for a pattern: the tag input arms prefilled with
/// the pane's directory and Enter commits it. A terminal writes its plaintext
/// scrollback and stays a terminal; an output buffer writes its rows and stays
/// an output buffer, still refillable and still walked by n/N — with the one
/// exception the New scratch has always been, an empty buffer whose whole
/// purpose is to become the file you name (output traits: `saves`).
///
/// Images and PDFs hold nothing of their own that is unwritten, so the word is
/// inert there and absent from their tag.
pub const Save = struct {
    pub const takes_arg = true;
    pub fn run(c: Ctx) void {
        const path = std.mem.trim(u8, c.arg orelse "", " \t\r\n");
        if (path.len > 0) return c.p.saveTo(c.id, path);
        if (c.pane.file) |file| if (file.output == null) return c.p.saveFile(c.id);
        if (c.pane.file != null or c.pane.isTerminal()) c.p.startSavePrompt(c.pane);
    }
};

/// An empty scratch buffer below the calling pane, inheriting its directory.
/// No file exists yet, so Save asks for a path prefilled with that directory
/// and, once written, the buffer becomes an ordinary file pane.
pub const New = struct {
    pub const output: OutputTraits = .{ .name = config.scratch_buffer, .doc = true, .saves = true };
    pub fn run(c: Ctx) void {
        c.p.newScratchBelow(c.id);
    }
};

/// The same empty scratch, opened in a fresh column beside the calling pane.
pub const Newcol = struct {
    pub fn run(c: Ctx) void {
        c.p.newScratchColumn(c.id);
    }
};

pub const Del = struct {
    pub fn run(c: Ctx) void {
        c.p.absorbVWeight(c.id);
        c.p.layoutRemove(c.id);
        c.p.deinitPane(c.pane);
        c.p.panes[c.id] = null;
        if (c.p.active == c.id) c.p.active = c.p.prevFocus(c.id) orelse {
            c.p.quit = true;
            c.p.emit(.quit);
            return;
        };
    }
};

/// Project this terminal's displayed cell foregrounds and backgrounds through
/// the current Pardes theme. The emulator keeps its original colour state;
/// only this pane's rendered cells change, so OSC queries and later resets
/// remain truthful.
pub const Filter = struct {
    pub fn run(c: Ctx) void {
        if (!c.pane.isTerminal()) return;
        c.pane.tty_filter = !c.pane.tty_filter;
    }
};

pub const Delcol = struct {
    pub fn run(c: Ctx) void {
        const f = c.p.layoutFindTerm(c.id) orelse return;
        var ids: [pardes.MAX_PANES]usize = undefined;
        const nids = c.p.col_n[f.col];
        for (0..nids) |k| ids[k] = c.p.col_terms[f.col][k];
        for (ids[0..nids]) |tid| {
            if (c.p.panes[tid]) |tt| {
                c.p.layoutRemove(tid);
                c.p.deinitPane(tt);
                c.p.panes[tid] = null;
            }
        }
        if (c.p.panes[c.p.active] == null) c.p.active = c.p.prevFocus(c.p.active) orelse {
            c.p.quit = true;
            c.p.emit(.quit);
            return;
        };
    }
};

/// A shell in the calling pane's directory, raw from the first frame. On every
/// pane's tagline: the fast path from wherever you are to a prompt there.
pub const Newtty = struct {
    pub fn run(c: Ctx) void {
        c.p.spawnTty(c.id);
    }
};

/// Fold the active pane's column into the one on its right, keeping its panes.
/// The horizontal mirror of the vertical stacking `New` does.
pub const Joincol = struct {
    pub fn run(c: Ctx) void {
        c.p.joinCol();
    }
};

pub const Tutor = struct {
    pub fn run(c: Ctx) void {
        const free = c.p.freeSlot() orelse return;
        const nt = c.p.openTutorView(free) catch return;
        c.p.placeDoc(c.id, free, nt); // a doc like any other
    }
};

pub const Help = struct {
    pub const output: OutputTraits = .{ .name = config.help_buffer };
    pub fn run(c: Ctx) void {
        output_pane.openHelp(c.p, c.id, "") catch |err| c.p.reportError(c.id, "help", err);
    }
};

/// Where pardes read its startup commands from — the path, printed into an
/// output buffer, `SPC f c` or the word executed anywhere.
///
/// The one question docs/config.md cannot answer, because the answer depends
/// on the machine: XDG_CONFIG_HOME if it is set and absolute, else
/// ~/Library/Application Support/pardes/init on macOS and
/// ~/.config/pardes/init everywhere else. Printing it beats documenting it —
/// the row is ordinary text, so a right click on it opens the file, and when
/// there is no file there yet the path is still exactly what you needed to
/// know.
pub const Config = struct {
    pub const output: OutputTraits = .{ .name = config.config_buffer };
    pub fn run(c: Ctx) void {
        output_pane.openConfig(c.p, c.id) catch |err| c.p.reportError(c.id, "config", err);
    }
};

/// This build's version and what changed to reach it, printed into an output
/// buffer the same way Config prints the live settings.
pub const Changelog = struct {
    pub const output: OutputTraits = .{ .name = config.changelog_buffer };
    pub fn run(c: Ctx) void {
        output_pane.openChangelog(c.p, c.id) catch |err| c.p.reportError(c.id, "changelog", err);
    }
};

/// Source code for the concrete backend implementation of a Panel*/scene
/// effect. The bytes are embedded at build time, so this works from an
/// installed executable rather than depending on a source checkout.
pub const EffectCode = struct {
    pub const takes_arg = true;
    pub const enabled = capabilities.panel_transitions or capabilities.scene_shaders;
    pub const output: OutputTraits = .{ .name = config.effect_code_buffer };
    pub fn run(c: Ctx) void {
        if (comptime enabled)
            output_pane.openEffectCode(c.p, c.id, c.arg orelse return) catch |err|
                c.p.reportError(c.id, "effect code", err)
        else
            unreachable;
    }
};

// ---- search ----

// The two builtins that ASK for something — Find walks file NAMES under this
// pane's directory, Grep file CONTENTS under every pane's. With an argument
// there is nothing to ask: it IS the pattern, so the walk runs now (this is
// what a `Grep` executed with a selection chorded to it means). Without one
// they arm the same tag input `/` does, and Enter runs it (submitSearch).

pub const Find = struct {
    pub const takes_arg = true;
    pub const output: OutputTraits = .{ .name = config.search_buffer, .steps = true };
    pub fn run(c: Ctx) void {
        const pat = std.mem.trim(u8, c.arg orelse "", " \t\r\n");
        if (pat.len > 0) return c.p.runSearch(c.id, pat, .find, .top) catch |err|
            c.p.reportError(c.id, "find", err);
        c.p.startSearch(c.pane, config.find_marker);
    }
};

/// Find's sibling: Find matches file NAMES under this pane's directory, Grep
/// matches file CONTENTS under every pane's directory at once.
pub const Grep = struct {
    pub const takes_arg = true;
    pub const output: OutputTraits = .{ .name = config.search_buffer, .steps = true };
    pub fn run(c: Ctx) void {
        const pat = std.mem.trim(u8, c.arg orelse "", " \t\r\n");
        if (pat.len > 0) return c.p.runSearch(c.id, pat, .grep, .top) catch |err|
            c.p.reportError(c.id, "grep", err);
        c.p.startSearch(c.pane, config.grep_marker);
    }
};

// ---- the window group ----

// The DESTINATION is the name — a word, the way a tag holds Del or Save —
// because these names live in the same vocabulary as everything else here:
// `Wh` would be a leader key path leaking into the text you can middle-click.
// Plain English words are safe for exactly these five: focus is the cheapest
// thing to change by accident (nothing is edited, closed or written) and the
// way back is the opposite word.

pub const Left = struct {
    pub fn run(c: Ctx) void {
        c.p.focusDir(c.id, .left);
    }
};

pub const Down = struct {
    pub fn run(c: Ctx) void {
        c.p.focusDir(c.id, .down);
    }
};

pub const Up = struct {
    pub fn run(c: Ctx) void {
        c.p.focusDir(c.id, .up);
    }
};

pub const Right = struct {
    pub fn run(c: Ctx) void {
        c.p.focusDir(c.id, .right);
    }
};

// ---- the jump group ----

// Where focus HAS BEEN, as three verbs and a list over the one stack pardes
// keeps (Pardes.jumps — see trackJump for what gets onto it). Builtins rather
// than bare key handlers for the same reason the four directions are: one
// implementation, reachable by chord, by `SPC j ...`, and by executing the
// word wherever it is written.

/// Ctrl-o: one step back into the history.
pub const Back = struct {
    pub fn run(c: Ctx) void {
        c.p.jumpBy(-1);
    }
};

/// Ctrl-i: one step forward again, up to wherever Back started.
pub const Forward = struct {
    pub fn run(c: Ctx) void {
        c.p.jumpBy(1);
    }
};

/// vim's Ctrl-^: the pane you were in before this one, whichever it was — the
/// hop you press twice a minute and never want to count steps for. Body-normal
/// Esc is this, which is what makes alternating between two panes one key you
/// hold down: two files, or a file and its shell, or a file and a +Search.
///
/// It does NOT move the stack cursor: it goes somewhere, so trackJump records
/// it like any other move, and that is exactly what makes it an involution —
/// after the hop, the pane you came from is the newest OTHER pane, so pressing
/// it again comes straight back. Back/Forward walk history; this one makes it.
///
/// It replaced a `Toggleterm` that hopped specifically between the newest DOC
/// and the newest TERMINAL. That distinction never earned its keep: it made Esc
/// unpredictable (which of three panes you landed on depended on their kinds),
/// and it could not alternate between two files at all — the case you hit most.
/// "The pane before this one" needs no kinds and is the same key twice.
pub const Last = struct {
    pub fn run(c: Ctx) void {
        var i = c.p.njumps;
        while (i > 0) {
            i -= 1;
            const j = c.p.jumps[i];
            if (j.pane != c.id) return c.p.focusPaneLine(j.pane, .{ .line = j.line, .col = j.col });
        }
    }
};

/// The same stack, as text you can read and click. Not a copy of it and not a
/// second list kept in step — the buffer is RENDERED from the stack when you
/// ask, the way +Search is rendered from a walk.
pub const Jumplist = struct {
    pub const output: OutputTraits = .{ .name = config.jumps_buffer, .steps = true };
    pub fn run(c: Ctx) void {
        output_pane.openJumps(c.p, c.id) catch |err| c.p.reportError(c.id, "jumplist", err);
    }
};

// ---- the language group ----

// Reached as `SPC l <helix's letter>` — see leader_path for why the prefix
// exists. They are builtins rather than bare keys for the same reason Save is
// one: the word is executable wherever it appears, so a middle-click on
// `Hover` in a tag does what `SPC l k` does. The five GOTOS are not here —
// helix binds them under `g` as motions, and a motion has no business being a
// word you can click.
//
// Most of them are one call: ask, and let the answer land in lspResponse.
// Nothing here blocks or knows what a backend is — swapping backends changes
// lsp.query and not one line below.

pub const Hover = struct {
    pub fn run(c: Ctx) void {
        c.p.lspRequest(c.id, .hover, "");
    }
};

pub const CodeAction = struct {
    pub fn run(c: Ctx) void {
        c.p.lspRequest(c.id, .code_action, "");
    }
};

pub const SelectRefs = struct {
    pub fn run(c: Ctx) void {
        c.p.lspRequest(c.id, .select_refs, "");
    }
};

pub const Symbols = struct {
    pub fn run(c: Ctx) void {
        c.p.lspRequest(c.id, .document_symbols, "");
    }
};

pub const Diagnostics = struct {
    pub fn run(c: Ctx) void {
        c.p.lspRequest(c.id, .diagnostics, "");
    }
};

pub const WsDiagnostics = struct {
    pub fn run(c: Ctx) void {
        c.p.lspRequest(c.id, .workspace_diagnostics, "");
    }
};

// The two that need a word from the user, handled exactly the way Find and
// Grep are: an argument means run it now (a selection chorded onto the name),
// no argument arms the tag input and Enter submits (submitSearch).

pub const Rename = struct {
    pub const takes_arg = true;
    pub fn run(c: Ctx) void {
        const a = std.mem.trim(u8, c.arg orelse "", " \t\r\n");
        if (a.len > 0) return c.p.lspRequest(c.id, .rename, a);
        c.p.startSearch(c.pane, config.rename_marker);
    }
};

pub const WsSymbols = struct {
    pub const takes_arg = true;
    pub fn run(c: Ctx) void {
        const a = std.mem.trim(u8, c.arg orelse "", " \t\r\n");
        if (a.len > 0) return c.p.lspRequest(c.id, .workspace_symbols, a);
        c.p.startSearch(c.pane, config.symbol_marker);
    }
};

// Introspection. A language backend that answers nothing looks exactly like
// one that is broken — from the outside, `gd` doing nothing is both "there is
// no definition" and "the analyser threw and we swallowed it". These two are
// how you tell: Lspinfo says what the backend IS, Lspwhy says what it just DID
// and where it stopped.

pub const Lspinfo = struct {
    pub fn run(c: Ctx) void {
        c.p.lspRequest(c.id, .status, "");
    }
};

pub const Lspwhy = struct {
    pub fn run(c: Ctx) void {
        c.p.lspRequest(c.id, .explain, "");
    }
};

// ---- the machine's address space (bare metal only) ----
//
// Three words gated by `board_memory.enabled`, which is a fact about the
// TARGET (freestanding, and not wasm) rather than about `pardes.platform` —
// see the reasoning there. Today that is exactly `-Dplatform=p4`; what makes
// it the right predicate is that a second bare-metal port gets them without
// anyone remembering to add an enum arm, and the browser never does.
// Elsewhere they are absent from the command enum, the help index, the leader
// table and the dispatcher, which is the gate ThemeFile and DumpThemes
// already use.
//
// They are not a debugger and not a privilege: with no OS there is no MMU, no
// supervisor and no process, so pardes IS the system software and all 2^32
// addresses are already its own. RAM, the peripheral registers behind the
// console it is talking to you over, and its own .text are one flat space, and
// a word that could reach only part of it would be pretending to be an
// application. What you actually reach for these for is the case a hosted
// editor never has: the display did not come up, and the question is whether
// the register you thought you wrote holds what you thought you wrote.
//
// Implementation, parsing, the volatile accesses and the clamp are all in
// board_memory.zig, the way the PDF words live in pdf_pane.zig — these three
// structs are the words, their argument contract, and where the answer goes.

/// `Peek <addr> [count]` — count 32-bit words (default 1) as `addr: value`
/// rows, hex or decimal address, refused rather than trapped when unaligned.
pub const Peek = struct {
    pub const takes_arg = true;
    pub const enabled = board_memory.enabled;
    pub const output: OutputTraits = .{ .name = config.peek_buffer };
    pub fn run(c: Ctx) void {
        if (comptime enabled) apply(c) else unreachable;
    }
    fn apply(c: Ctx) void {
        board_memory.peek(c.p, c.id, c.arg orelse "") catch |err|
            c.p.reportError(c.id, "peek", err);
    }
};

/// `Poke <addr> <value>` — one 32-bit store, answered on the message row with
/// the value written AND the value that reads back, which on MMIO is the
/// interesting half (see board_memory.poke).
pub const Poke = struct {
    pub const takes_arg = true;
    pub const enabled = board_memory.enabled;
    pub fn run(c: Ctx) void {
        if (comptime enabled) apply(c) else unreachable;
    }
    fn apply(c: Ctx) void {
        board_memory.poke(c.p, c.id, c.arg orelse "") catch |err|
            c.p.reportError(c.id, "poke", err);
    }
};

/// `Hexdump <addr> [len]` — len bytes (default 256) in `hexdump -C`'s layout.
pub const Hexdump = struct {
    pub const takes_arg = true;
    pub const enabled = board_memory.enabled;
    pub const output: OutputTraits = .{ .name = config.hexdump_buffer };
    pub fn run(c: Ctx) void {
        if (comptime enabled) apply(c) else unreachable;
    }
    fn apply(c: Ctx) void {
        board_memory.hexdump(c.p, c.id, c.arg orelse "") catch |err|
            c.p.reportError(c.id, "hexdump", err);
    }
};