//! Image panes: their owned pixels, PETSCII cache, lifecycle, and two render
//! paths. Core layout supplies the body rectangle; this module fills it or
//! attaches one native image to it.
const std = @import("std");
const pardes = @import("pardes.zig");
const image = @import("image.zig");
const look = @import("look.zig");
const dump = @import("dump.zig");
const config = @import("config.zig");

const GridKey = struct {
    cols: u16 = 0,
    rows: u16 = 0,
    palette: image.PaletteMode = .commodore,
    ascii: bool = true,
};

/// The decoded, downscaled RGBA is retained so changing the pane size or one
/// of the glyph-renderer toggles can rebuild the PETSCII projection without
/// decoding the source again. All slices are owned by Pardes.image_gpa.
pub const State = struct {
    path: []u8,
    petscii: bool = false,
    pmode: image.PaletteMode = .commodore,
    ascii: bool = true,
    tried: bool = false,
    rgba: []u8 = &.{},
    iw: usize = 0,
    ih: usize = 0,
    /// Dump-loaded bytes, decoded lazily by the same path as a disk image.
    raw: []u8 = &.{},
    grid: image.petscii.Grid = .{ .cells = &.{}, .gw = 0, .gh = 0 },
    grid_key: GridKey = .{},

    pub fn deinit(state: *State, gpa: std.mem.Allocator) void {
        gpa.free(state.path);
        if (state.rgba.len > 0) gpa.free(state.rgba);
        if (state.raw.len > 0) gpa.free(state.raw);
        if (state.grid.cells.len > 0) gpa.free(state.grid.cells);
        state.* = undefined;
    }
};

/// Construct an image pane from a path and optionally transferred dump bytes.
/// `raw` must be image_gpa-owned and ownership transfers only on success.
pub fn create(p: *pardes.Pardes, id: usize, path: []const u8, raw: []u8) !*pardes.Pane {
    const path_copy = try p.image_gpa.dupe(u8, path);
    errdefer p.image_gpa.free(path_copy);
    const pane = try p.newDocPane(id);
    pane.image = .{ .path = path_copy, .raw = raw };
    return pane;
}

/// Serialize the binary image record used by images and, for dump-schema
/// compatibility, PDFs. Common pane metadata is supplied by the core.
pub fn dumpPane(
    arena: std.mem.Allocator,
    pane: *const pardes.Pane,
    tag: []const u8,
    body: []const u8,
    scroll: usize,
    path: []const u8,
    raw: []const u8,
) !dump.Pane {
    const bytes = if (raw.len > 0) raw else look.readFile(arena, path) catch "";
    return .{
        .kind = .image,
        .tag = tag,
        .body = body,
        .scroll = scroll,
        .cols = pane.cols,
        .rows = pane.rows,
        .vweight = pane.vweight,
        .image = .{
            .path = path,
            .bytes_b64 = if (bytes.len > 0) try dump.encodeBytes(arena, bytes) else "",
            .petscii = if (pane.image) |state| state.petscii else false,
            .palette = if (pane.image) |state| switch (state.pmode) {
                .commodore => .commodore,
                .terminal => .terminal,
            } else .commodore,
            .ascii = if (pane.image) |state| state.ascii else true,
        },
    };
}

/// Rebuild an ordinary raster image from its dump record. PDF records share
/// the schema for compatibility and are deliberately dispatched by the core
/// before reaching this function.
pub fn restore(p: *pardes.Pardes, id: usize, src: dump.Pane) !*pardes.Pane {
    const saved = src.image.?;
    var raw: []u8 = if (saved.bytes_b64.len > 0)
        try dump.decodeBytes(p.image_gpa, saved.bytes_b64)
    else
        &.{};
    errdefer if (raw.len > 0) p.image_gpa.free(raw);
    const pane = try create(p, id, saved.path, raw);
    raw = &.{};
    pane.image.?.petscii = saved.petscii;
    pane.image.?.pmode = switch (saved.palette) {
        .commodore => .commodore,
        .terminal => .terminal,
    };
    pane.image.?.ascii = saved.ascii;
    pane.cols = @max(1, src.cols);
    pane.rows = @max(1, src.rows);
    return pane;
}

pub fn togglePetscii(state: *State) void {
    state.petscii = !state.petscii;
}

pub fn togglePalette(state: *State) void {
    state.pmode = if (state.pmode == .commodore) .terminal else .commodore;
}

pub fn toggleAscii(state: *State) void {
    state.ascii = !state.ascii;
}

/// Image renderer choices are pane-local, not global Config values. Keep them
/// queryable where they apply: the live tag beside the image's path.
pub fn tagPrefix(arena: std.mem.Allocator, state: *const State) ![]u8 {
    return std.fmt.allocPrint(
        arena,
        "{s} petscii:{s} palette:{s} ascii:{s} {s}",
        .{
            config.tag_image,
            if (state.petscii) "on" else "off",
            @tagName(state.pmode),
            if (state.ascii) "on" else "off",
            state.path,
        },
    );
}

/// Prefix written by version-1 dumps before renderer choices became visible
/// in the live tag. Returned as a borrowed slice of saved_tag for one-time
/// custom-tail migration.
pub fn legacySavedPrefix(state: *const State, saved_tag: []const u8) ?[]const u8 {
    const lead = config.tag_image ++ " ";
    if (!std.mem.startsWith(u8, saved_tag, lead)) return null;
    const path_at = lead.len;
    if (!std.mem.startsWith(u8, saved_tag[path_at..], state.path)) return null;
    return saved_tag[0 .. path_at + state.path.len];
}

fn ensureDecoded(p: *pardes.Pardes, state: *State) void {
    if (state.tried) return;
    state.tried = true;
    const bytes: []const u8 = if (state.raw.len > 0)
        state.raw
    else
        look.readFile(p.scratch.allocator(), state.path) catch "";
    if (image.decode(p.image_gpa, bytes)) |decoded| {
        state.rgba = decoded.rgba;
        state.iw = decoded.w;
        state.ih = decoded.h;
    }
}

fn ensureGrid(p: *pardes.Pardes, state: *State, cols: u16, rows: u16) void {
    const wanted = GridKey{ .cols = cols, .rows = rows, .palette = state.pmode, .ascii = state.ascii };
    if (state.grid.cells.len > 0 and std.meta.eql(state.grid_key, wanted)) return;
    if (state.grid.cells.len > 0) p.image_gpa.free(state.grid.cells);
    const palette = switch (state.pmode) {
        .commodore => image.petscii.commodore,
        .terminal => image.ansiPalette(),
    };
    state.grid = image.petscii.render(
        p.image_gpa,
        state.rgba,
        state.iw,
        state.ih,
        cols,
        rows,
        palette,
        state.ascii,
    ) catch .{ .cells = &.{}, .gw = 0, .gh = 0 };
    state.grid_key = wanted;
}

/// Render the image body supplied by core layout. Native-capable hosts receive
/// a pixel attachment; other hosts and explicit PETSCII mode receive cells.
pub fn draw(
    p: *pardes.Pardes,
    state: *State,
    pane_id: u8,
    serial: u32,
    x: u16,
    y: u16,
    cols: u16,
    rows: u16,
) void {
    ensureDecoded(p, state);
    if (state.rgba.len == 0 or cols == 0 or rows == 0) return;
    if (!state.petscii and p.native_images) {
        _ = p.appendImagePlace(.{
            .pane = pane_id,
            .serial = serial,
            .x = x,
            .y = y,
            .w = cols,
            .h = rows,
            .rgba = state.rgba,
            .iw = state.iw,
            .ih = state.ih,
        });
        return;
    }

    ensureGrid(p, state, cols, rows);
    if (state.grid.cells.len == 0) return;
    const offx = if (cols > state.grid.gw) (@as(usize, cols) - state.grid.gw) / 2 else 0;
    const offy = if (rows > state.grid.gh) (@as(usize, rows) - state.grid.gh) / 2 else 0;
    for (0..state.grid.gh) |cy| for (0..state.grid.gw) |cx| {
        const cell = &state.grid.cells[cy * state.grid.gw + cx];
        const fg: pardes.Color = switch (state.pmode) {
            .commodore => .{ .rgb = image.petscii.commodore[cell.fg] },
            .terminal => .{ .index = cell.fg },
        };
        const bg: pardes.Color = switch (state.pmode) {
            .commodore => .{ .rgb = image.petscii.commodore[cell.bg] },
            .terminal => .{ .index = cell.bg },
        };
        const sx = x + @as(u16, @intCast(offx + cx));
        const sy = y + @as(u16, @intCast(offy + cy));
        if (sx < p.surface.cols and sy < p.surface.rows)
            p.surface.set(sx, sy, cell.glyph[0..cell.glen], .{ .fg = fg, .bg = bg });
    };
}

test "pane-local renderer choices are visible in the image tag" {
    var state: State = .{ .path = @constCast("/tmp/picture.ppm") };
    togglePetscii(&state);
    togglePalette(&state);
    toggleAscii(&state);
    const tag = try tagPrefix(std.testing.allocator, &state);
    defer std.testing.allocator.free(tag);
    try std.testing.expectEqualStrings(
        config.tag_image ++ " petscii:on palette:terminal ascii:off /tmp/picture.ppm",
        tag,
    );
    try std.testing.expectEqualStrings(
        "img /tmp/picture.ppm",
        legacySavedPrefix(&state, "img /tmp/picture.ppm Keep Del").?,
    );
}

test "dump restore propagates malformed embedded image bytes" {
    const p = try pardes.Pardes.init(std.testing.allocator, .{ .tty_only = true });
    defer p.deinit();
    try std.testing.expect(p.panes[1] == null);
    try std.testing.expectError(error.InvalidCharacter, restore(p, 1, .{
        .kind = .image,
        .tag = "img /tmp/bad.ppm",
        .body = "",
        .image = .{ .path = "/tmp/bad.ppm", .bytes_b64 = "A..A" },
    }));
    try std.testing.expect(p.panes[1] == null);
}