//! Image panes. Decoding is zstbi (C stb_image) to RGBA, downscaled; the kept
//! pixels render as PETSCII glyph art directly into the Surface — or, when the
//! host has kitty graphics (and Petscii isn't toggled), ride the Surface as a
//! pixel attachment the shell transmits/places (tty: vaxis kitty; SDL: blit).
const std = @import("std");
const zstbi = @import("zstbi");
const ghostty_vt = @import("ghostty-vt");
pub const petscii = @import("petscii.zig");

/// the terminal's own 16 ANSI colors — what the `terminal` palette mode
/// scores against; cells then paint as indexed colors so the real terminal
/// resolves the RGB
pub fn ansiPalette() [16][3]u8 {
    var p: [16][3]u8 = undefined;
    for (0..16) |i| {
        const c = ghostty_vt.color.default[i];
        p[i] = .{ c.r, c.g, c.b };
    }
    return p;
}

/// cap the longest side before keeping/transmitting: a pane is at most a
/// screenful of cells, multi-thousand-pixel photos waste decode/transmit time
const MAX_DIM: u32 = 1280;

pub const PaletteMode = enum { commodore, terminal };

/// call once at startup / exit (stb_image's allocator shim)
pub fn start(io: std.Io, gpa: std.mem.Allocator) void {
    zstbi.init(io, gpa);
}
pub fn stop() void {
    zstbi.deinit();
}

/// decode + downscale to RGBA, gpa-owned. Returns null on any failure — the
/// pane then simply shows a blank body.
pub fn decode(gpa: std.mem.Allocator, bytes: []const u8) ?struct { rgba: []u8, w: usize, h: usize } {
    if (bytes.len == 0) return null;
    var img = zstbi.Image.loadFromMemory(bytes, 4) catch return null; // 4 = RGBA
    defer img.deinit();
    var scaled: ?zstbi.Image = null;
    defer if (scaled) |*s| s.deinit();
    const longest = @max(img.width, img.height);
    const src: *const zstbi.Image = if (longest > MAX_DIM) blk: {
        const nw = @max(1, img.width * MAX_DIM / longest);
        const nh = @max(1, img.height * MAX_DIM / longest);
        scaled = img.resize(nw, nh);
        break :blk &scaled.?;
    } else &img;
    const rgba = gpa.dupe(u8, src.data) catch return null;
    return .{ .rgba = rgba, .w = src.width, .h = src.height };
}