// search.zig — inline 18-line TUI widget, no alternate screen
// Raw terminal mode for interactive key handling (POSIX: linux + macos).
const std = @import("std");
const types = @import("types.zig");
const output = @import("output.zig");
const api = @import("api.zig");

const WIDGET_LINES: usize = 18;
const RESULT_ROWS: usize = 5;
const STDIN_FD = std.posix.STDIN_FILENO;

// Debounce window: a keystroke defers the nix search until typing pauses this
// long. nix search is synchronous and blocks the widget for ~1s, so the window
// must be long enough that a normal between-keystroke pause doesn't trigger it —
// it should only fire once you've actually stopped typing.
const DEBOUNCE_MS: i64 = 500;

// Milliseconds elapsed since `since` on the monotonic (awake) clock. std has no
// milliTimestamp in 0.16; this mirrors the Io.Clock pattern used in apply().
fn elapsedMs(io: std.Io, since: std.Io.Timestamp) i64 {
    const ns = @max(0, since.untilNow(io, .awake).toNanoseconds());
    return @intCast(@divFloor(ns, 1_000_000));
}

// What the detail pane shows for the selected package. Tab toggles between the
// collapsed (description) view and the expanded meta view; the latter is fetched
// on demand, so it passes through loading and (on eval failure) unavailable.
const Detail = union(enum) {
    collapsed,
    loading,
    unavailable,
    meta: api.PkgMeta,
};

pub fn run(
    gpa: std.mem.Allocator,
    io: std.Io,
    initial_query: []const u8,
    mode: Mode,
    environ: *const std.process.Environ.Map,
) !?types.NixPackage {
    // Non-interactive fallback: when stdin isn't a terminal (piped, scripted,
    // CI), print plain results and return instead of the raw-mode widget, which
    // needs a real tty and would block waiting for keys.
    if (!stdinIsTty(io)) return runPlain(gpa, io, initial_query, mode, environ);

    var saved: std.posix.termios = undefined;
    try rawModeEnable(STDIN_FD, &saved);
    defer rawModeDisable(STDIN_FD, saved);

    var arena = std.heap.ArenaAllocator.init(gpa);
    defer arena.deinit();

    var query_buf: [256]u8 = undefined;
    var query_len: usize = @min(initial_query.len, query_buf.len - 1);
    @memcpy(query_buf[0..query_len], initial_query[0..query_len]);

    var packages: []types.NixPackage = &.{};
    var opts: []api.NixOption = &.{};
    var selection: usize = 0;

    // Expanded detail (Tab): the selected package's meta, fetched on demand into
    // its own arena and cached by attr so re-visiting is instant. Kept separate
    // from the search arena, which is reset on every new search.
    var expanded = false;
    var meta_arena = std.heap.ArenaAllocator.init(gpa);
    defer meta_arena.deinit();
    var meta: ?api.PkgMeta = null;
    var meta_attr: []const u8 = "";

    // Initial search
    _ = arena.reset(.free_all);
    packages = doSearch(arena.allocator(), io, query_buf[0..query_len], mode, &opts, environ);

    // Initial render (prints WIDGET_LINES lines)
    renderWidget(query_buf[0..query_len], packages, opts, selection, mode, false, .collapsed);
    output.flush();

    // Key loop with debounced search. A keystroke marks the query dirty and
    // stamps the time; the nix search fires only once typing pauses for
    // DEBOUNCE_MS. Stale results stay on screen until the new search returns, so
    // there is no blank flash mid-typing.
    var chosen: ?types.NixPackage = null;
    var query_dirty = false;
    var query_changed_at = std.Io.Clock.awake.now(io);
    loop: while (true) {
        // Block until a key arrives, unless a search is pending — then wake when
        // the debounce window closes so we can fire it.
        var timeout_ms: i32 = -1;
        if (query_dirty) {
            const remaining = DEBOUNCE_MS - elapsedMs(io, query_changed_at);
            timeout_ms = if (remaining <= 0) 0 else @intCast(remaining);
        }

        var pfd = [_]std.posix.pollfd{.{ .fd = STDIN_FD, .events = std.posix.POLL.IN, .revents = 0 }};
        const ready = std.posix.poll(&pfd, timeout_ms) catch 0;

        if (ready == 0) {
            // Poll timed out. If no search is pending, nothing changed — keep waiting.
            if (!(query_dirty and elapsedMs(io, query_changed_at) >= DEBOUNCE_MS)) continue;
            query_dirty = false;
            // Paint "searching..." over the stale results before the blocking nix
            // search, so the ~1s pause reads as progress, not a freeze.
            output.cursorUp(WIDGET_LINES);
            renderWidget(query_buf[0..query_len], packages, opts, selection, mode, true, .collapsed);
            output.flush();

            _ = arena.reset(.free_all);
            packages = doSearch(arena.allocator(), io, query_buf[0..query_len], mode, &opts, environ);
            // New result set: reset to the top and drop cached meta (it belonged to
            // the previous results). Navigating during the window could otherwise
            // leave selection past the new end and renderWidget would index OOB.
            selection = 0;
            meta = null;
            // fall through to the common render below
        } else {
            var buf: [4]u8 = undefined;
            const n = std.posix.read(STDIN_FD, &buf) catch break;
            if (n == 0) break;

            // The query is a live text field, so every printable key types into it —
            // single-letter actions would collide with package names (the 'i' in
            // "ripgrep" must not trigger install). Only non-text keys act: Enter
            // selects, Tab expands detail, arrows navigate, Esc cancels.
            if (n >= 3 and buf[0] == 0x1b and buf[1] == '[') {
                switch (buf[2]) {
                    'A' => if (selection > 0) { selection -= 1; }, // up
                    'B' => if (selection + 1 < resultCount(packages, opts, mode)) { selection += 1; }, // down
                    else => {},
                }
            } else switch (buf[0]) {
                0x1b => break :loop, // Esc: cancel (chosen stays null)
                '\t' => expanded = !expanded, // Tab: toggle package detail
                '\r', '\n' => { // Enter: select the highlighted package
                    if (mode == .packages and packages.len > selection) {
                        chosen = packages[selection];
                    }
                    break :loop;
                },
                127, 8 => { // backspace
                    if (query_len > 0) {
                        query_len -= 1;
                        query_dirty = true;
                        query_changed_at = std.Io.Clock.awake.now(io);
                        selection = 0;
                    }
                },
                else => |ch| {
                    if (ch >= 32 and ch < 127 and query_len < query_buf.len - 1) {
                        query_buf[query_len] = ch;
                        query_len += 1;
                        query_dirty = true;
                        query_changed_at = std.Io.Clock.awake.now(io);
                        selection = 0;
                    }
                },
            }
        }

        // Common render after a search or a key. When expanded, resolve the detail
        // pane by fetching the selected package's meta on demand (blocking eval),
        // painting a "loading" frame first and caching by attr so re-visiting is
        // instant.
        const count = resultCount(packages, opts, mode);
        const sel = if (count == 0) 0 else @min(selection, count - 1);
        var detail: Detail = .collapsed;
        if (expanded and mode == .packages and count > 0) {
            const cur = packages[sel].attr;
            if (meta == null or !std.mem.eql(u8, meta_attr, cur)) {
                output.cursorUp(WIDGET_LINES);
                renderWidget(query_buf[0..query_len], packages, opts, selection, mode, false, .loading);
                output.flush();
                _ = meta_arena.reset(.free_all);
                meta_attr = meta_arena.allocator().dupe(u8, cur) catch "";
                meta = api.packageMeta(meta_arena.allocator(), io, cur);
            }
            detail = if (meta) |mm| Detail{ .meta = mm } else Detail.unavailable;
        }
        output.cursorUp(WIDGET_LINES);
        renderWidget(query_buf[0..query_len], packages, opts, selection, mode, false, detail);
        output.flush();
    }

    // Clear the widget area
    output.cursorUp(WIDGET_LINES);
    var i: usize = 0;
    while (i < WIDGET_LINES) : (i += 1) {
        output.raw(output.C_CLEAR_EOL ++ "\n");
    }
    output.cursorUp(WIDGET_LINES);
    output.flush();

    // The chosen package's strings live in the search arena, which deinits as this
    // function returns — dupe into the caller's allocator so it survives.
    if (chosen) |pkg| return dupePackage(gpa, pkg);
    return null;
}

fn dupePackage(gpa: std.mem.Allocator, pkg: types.NixPackage) types.NixPackage {
    return .{
        .attr = gpa.dupe(u8, pkg.attr) catch "",
        .pname = gpa.dupe(u8, pkg.pname) catch "",
        .version = gpa.dupe(u8, pkg.version) catch "",
        .description = gpa.dupe(u8, pkg.description) catch "",
    };
}

pub const Mode = enum { packages, options };

fn doSearch(arena: std.mem.Allocator, io: std.Io, query: []const u8, mode: Mode, opts: *[]api.NixOption, environ: *const std.process.Environ.Map) []types.NixPackage {
    // An empty query matches the entire catalog (100k+ rows) — a multi-second
    // fetch that would freeze the widget. Show nothing until there's a query.
    if (std.mem.trim(u8, query, " \t").len == 0) {
        opts.* = &.{};
        return &.{};
    }
    switch (mode) {
        .packages => return api.searchPackages(arena, io, environ, query) catch &.{},
        .options => {
            opts.* = api.searchOptions(arena, io, query) catch &.{};
            return &.{};
        },
    }
}

fn resultCount(packages: []types.NixPackage, opts: []api.NixOption, mode: Mode) usize {
    return switch (mode) {
        .packages => packages.len,
        .options => opts.len,
    };
}

fn stdinIsTty(io: std.Io) bool {
    return std.Io.File.stdin().isTty(io) catch false;
}

// Plain, non-interactive rendering for non-tty stdin. Same pink :: header and
// result count the widget shows, then one line per result; no cursor control.
fn runPlain(gpa: std.mem.Allocator, io: std.Io, query: []const u8, mode: Mode, environ: *const std.process.Environ.Map) !?types.NixPackage {
    // An empty query matches the entire catalog (100k+ rows); refuse it cleanly.
    if (std.mem.trim(u8, query, " \t").len == 0) {
        output.searchEmptyQuery();
        output.flush();
        return null;
    }
    var arena = std.heap.ArenaAllocator.init(gpa);
    defer arena.deinit();
    var opts: []api.NixOption = &.{};
    const packages = doSearch(arena.allocator(), io, query, mode, &opts, environ);
    const count = resultCount(packages, opts, mode);
    const mode_str = if (mode == .packages) "nixpkgs" else "options";
    output.searchPlainHeader(mode_str, query, count);
    if (count == 0) {
        output.searchPlainNoResults();
        output.flush();
        return null;
    }
    switch (mode) {
        // unfree=false: per-result meta.unfree would need an eval per package (too
        // slow for the list); the TUI detail pane is the place to surface it.
        .packages => for (packages) |pkg| output.searchPlainPackage(pkg.pname, pkg.version, pkg.description, false),
        .options => for (opts) |opt| output.searchPlainOption(opt.name, opt.type_str),
    }
    output.flush();
    return null;
}

// A key hint with dim brackets and a pink letter: dim '[', pink label, dim ']'.
// Comptime-built so it's a plain string literal — the widget always renders raw
// ANSI (it only runs on a real tty).
fn keyHint(comptime label: []const u8) []const u8 {
    return output.C_DIM ++ "[" ++ output.C_RESET ++ output.C_PINK ++ label ++ output.C_RESET ++ output.C_DIM ++ "]" ++ output.C_RESET;
}

fn renderWidget(query: []const u8, packages: []types.NixPackage, opts: []api.NixOption, selection: usize, mode: Mode, searching: bool, detail: Detail) void {
    const count = resultCount(packages, opts, mode);
    const CLR = output.C_CLEAR_EOL;
    const RST = output.C_RESET;
    const PKN = output.C_PINK;
    const BLD = output.C_BOLD;
    const DIM = output.C_DIM;
    const CYN = output.C_CYAN;

    // Clamp to the current result count: a caller could hand us a selection from a
    // larger, now-replaced result set. Never index past the end.
    const sel = if (count == 0) 0 else @min(selection, count - 1);

    // Line 1: header. While the (blocking) search runs, show "searching..." so the
    // pause reads as work-in-progress, not a frozen widget.
    output.raw(CLR);
    const mode_str = if (mode == .packages) "nixpkgs" else "options";
    if (searching) {
        output.p("{s}:: {s}search {s} {s}  {s}searching...{s}\n", .{
            PKN, RST, mode_str, query, DIM, RST,
        });
    } else {
        output.p("{s}:: {s}search {s} {s}  {s}{d} results{s}\n", .{
            PKN, RST, mode_str, query, DIM, count, RST,
        });
    }

    // Line 2: blank
    output.raw(CLR ++ "\n");

    // Lines 3-7: results (up to RESULT_ROWS), scrolled so selection stays visible
    const scroll: usize = if (sel >= RESULT_ROWS) sel - RESULT_ROWS + 1 else 0;
    var i: usize = 0;
    while (i < RESULT_ROWS) : (i += 1) {
        const idx = scroll + i;
        output.raw(CLR);
        if (idx < count) {
            const selected = (idx == sel);
            switch (mode) {
                .packages => {
                    const pkg = packages[idx];
                    const marker = if (selected) PKN ++ "> " ++ RST else "  ";
                    const name_pre = if (selected) PKN ++ BLD else "";
                    const name_suf = if (selected) RST else "";
                    output.p("   {s}{s}{s}{s}   {s}{s}{s}   {s}\n", .{ marker, name_pre, pkg.pname, name_suf, CYN, pkg.version, RST, pkg.description });
                },
                .options => {
                    const opt = opts[idx];
                    const marker = if (selected) PKN ++ "> " ++ RST else "  ";
                    output.p("   {s}{s}   {s}{s}{s}\n", .{ marker, opt.name, DIM, opt.type_str, RST });
                },
            }
        } else {
            output.raw("\n");
        }
    }

    // Line 8: blank
    output.raw(CLR ++ "\n");

    // Lines 9-12: selected package detail. Line 9 (name+version) is shared; the
    // next three lines depend on `detail`. Every arm emits exactly 3 lines so the
    // widget stays WIDGET_LINES tall.
    if (count > 0 and mode == .packages) {
        const pkg = packages[sel];
        output.raw(CLR);
        output.p("   {s}{s}{s}{s}  {s}{s}{s}\n", .{ PKN, BLD, pkg.pname, RST, CYN, pkg.version, RST });
        switch (detail) {
            .collapsed => {
                output.raw(CLR);
                output.p("   {s}\n", .{pkg.description});
                output.raw(CLR ++ "\n");
                output.raw(CLR);
                output.p("   {s}attr{s}  {s}{s}{s}\n", .{ DIM, RST, CYN, pkg.attr, RST });
            },
            .loading => {
                output.raw(CLR);
                output.p("   {s}loading details...{s}\n", .{ DIM, RST });
                output.raw(CLR ++ "\n");
                output.raw(CLR);
                output.p("   {s}attr{s}  {s}{s}{s}\n", .{ DIM, RST, CYN, pkg.attr, RST });
            },
            .unavailable => {
                output.raw(CLR);
                output.p("   {s}details unavailable{s}\n", .{ DIM, RST });
                output.raw(CLR ++ "\n");
                output.raw(CLR);
                output.p("   {s}attr{s}  {s}{s}{s}\n", .{ DIM, RST, CYN, pkg.attr, RST });
            },
            .meta => |m| {
                const home = if (m.homepage.len > 0) m.homepage else "—";
                const lic = if (m.license.len > 0) m.license else "—";
                output.raw(CLR);
                output.p("   {s}{s:<8}{s}{s}{s}{s}\n", .{ DIM, "home", RST, CYN, home, RST });
                output.raw(CLR);
                output.p("   {s}{s:<8}{s}{s}\n", .{ DIM, "license", RST, lic });
                output.raw(CLR);
                output.p("   {s}{s:<8}{s}{s}{s}{s}\n", .{ DIM, "attr", RST, CYN, pkg.attr, RST });
            },
        }
    } else if (count > 0 and mode == .options) {
        const opt = opts[sel];
        output.raw(CLR);
        output.p("   {s}  {s}{s}{s}\n", .{ opt.name, DIM, opt.type_str, RST });
        output.raw(CLR);
        output.p("   {s}\n", .{opt.description});
        output.raw(CLR ++ "\n");
        output.raw(CLR ++ "\n");
    } else {
        output.raw(CLR ++ "\n");
        output.raw(CLR ++ "\n");
        output.raw(CLR ++ "\n");
        output.raw(CLR ++ "\n");
    }

    // Line 13: blank
    output.raw(CLR ++ "\n");

    // Lines 14-17: controls + padding to reach WIDGET_LINES
    output.raw(CLR);
    if (mode == .packages) {
        output.p("   {s} install  {s} info  {s}[up/down]{s} nav  {s} cancel\n", .{
            keyHint("enter"), keyHint("tab"), DIM, RST, keyHint("esc"),
        });
    } else {
        output.p("   {s}[up/down]{s} nav  {s} cancel\n", .{ DIM, RST, keyHint("esc") });
    }
    // Padding to reach WIDGET_LINES (18)
    var pad: usize = 14;
    while (pad < WIDGET_LINES) : (pad += 1) {
        output.raw(CLR ++ "\n");
    }
}

fn rawModeEnable(fd: std.posix.fd_t, saved: *std.posix.termios) !void {
    var tio = try std.posix.tcgetattr(fd);
    saved.* = tio;
    // Same flag names exist on every POSIX termios target Zig exposes (linux,
    // macos, the *BSDs), so one body covers all of them — the old linux-only
    // guard left macos in cooked mode (echo on, line-buffered). OPOST is left
    // on so output keeps translating "\n" -> "\r\n" (cursor to column 0).
    tio.lflag.ECHO = false;
    tio.lflag.ICANON = false;
    tio.lflag.ISIG = false;
    tio.lflag.IEXTEN = false;
    tio.iflag.ICRNL = false;
    tio.iflag.IXON = false;
    tio.cc[@intFromEnum(std.posix.V.MIN)] = 1;
    tio.cc[@intFromEnum(std.posix.V.TIME)] = 0;
    try std.posix.tcsetattr(fd, .FLUSH, tio);
}

fn rawModeDisable(fd: std.posix.fd_t, saved: std.posix.termios) void {
    std.posix.tcsetattr(fd, .FLUSH, saved) catch {};
}