// BoardView (P4.3) — render the seeded match-3 board with real gem sprites.
//
// Modeled on game/chess/board_view.sx: a `View` that lays out an 8×8 grid and
// draws tiles/sprites through RenderContext.add_image / add_image_uv, sampling
// the gem sprite sheet by UV column. The background image fills the whole view;
// the grid is a centered square inside the safe-area inset.
#import "modules/std.sx";
#import "modules/math";
#import "modules/opengl.sx";
#import "modules/stb.sx";
#import "modules/gpu/types.sx";
#import "modules/gpu/api.sx";
#import "modules/ui/types.sx";
#import "modules/ui/render.sx";
#import "modules/ui/events.sx";
#import "modules/ui/view.sx";
#import "board.sx";

// Fraction of a cell each gem occupies; the remainder is margin so a gem sits
// inside its cell tile rather than touching the tile's edges.
GEM_FILL_FRAC :f32: 0.84;

// UV sub-rect of one gem column, spanning the sheet's full height.
GemUV :: struct {
    uv_min: Point;
    uv_max: Point;
}

// Loads and holds the three board textures (background, cell tile, gem sheet)
// and maps a gem index to its column UV. Modeled on chess's ChessPieces.
BoardAssets :: struct {
    bg_tex: u32;
    cell_tex: u32;
    gems_tex: u32;
    cell_u: f32;
    loaded: bool;

    init :: (self: *BoardAssets) {
        self.bg_tex = 0;
        self.cell_tex = 0;
        self.gems_tex = 0;
        // gems.png is GEM_COUNT columns wide and one row tall, so a gem's UV
        // column IS its gem index (0=red … 5=purple); cell_u is one column wide.
        self.cell_u = 1.0 / cast(f32) GEM_COUNT;
        self.loaded = false;
    }

    load :: (self: *BoardAssets, gpu: ?GPU) {
        self.bg_tex = load_texture("assets/board/background.png", gpu);
        self.cell_tex = load_texture("assets/board/cell.png", gpu);
        self.gems_tex = load_texture("assets/gems/gems.png", gpu);
        self.loaded = self.bg_tex != 0 and self.cell_tex != 0 and self.gems_tex != 0;
    }

    gem_uv :: (self: *BoardAssets, index: s64) -> GemUV {
        u0 : f32 = xx index * self.cell_u;
        GemUV.{
            uv_min = Point.{ x = u0, y = 0.0 },
            uv_max = Point.{ x = u0 + self.cell_u, y = 1.0 }
        }
    }
}

// Decode an RGBA image and upload it as a texture, returning the handle (0 on
// failure). When a GPU backend is bound (iOS Metal) it owns the upload; the
// desktop GL path falls back to a plain GL_TEXTURE_2D.
load_texture :: (path: [:0]u8, gpu: ?GPU) -> u32 {
    w : s32 = 0;
    h : s32 = 0;
    ch : s32 = 0;
    pixels := stbi_load(path, @w, @h, @ch, 4);
    if pixels == null {
        out("WARNING: could not load texture: ");
        out(path);
        out("\n");
        return 0;
    }

    tex : u32 = 0;
    if gpu != null {
        tex = gpu.create_texture(w, h, .rgba8, xx pixels);
    } else {
        glGenTextures(1, @tex);
        glBindTexture(GL_TEXTURE_2D, tex);
        glTexImage2D(GL_TEXTURE_2D, 0, xx GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, xx GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, xx GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, xx GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, xx GL_CLAMP_TO_EDGE);
    }

    stbi_image_free(pixels);
    return tex;
}

BoardView :: struct {
    board: *Board;
    assets: *BoardAssets;
    safe: EdgeInsets;

    cell_size: f32;
    origin: Point;

    // Center a square 8×8 grid inside the safe-area-inset region of `frame`.
    compute_layout :: (self: *BoardView, frame: Frame) {
        avail := frame.inset(self.safe);
        cols : f32 = xx BOARD_COLS;
        board_dim := min(avail.size.width, avail.size.height);
        self.cell_size = board_dim / cols;
        total := self.cell_size * cols;
        self.origin = Point.{
            x = avail.origin.x + (avail.size.width - total) * 0.5,
            y = avail.origin.y + (avail.size.height - total) * 0.5
        };
    }

    cell_frame :: (self: *BoardView, col: s64, row: s64) -> Frame {
        Frame.make(
            self.origin.x + xx col * self.cell_size,
            self.origin.y + xx row * self.cell_size,
            self.cell_size,
            self.cell_size
        )
    }
}

impl View for BoardView {
    size_that_fits :: (self: *BoardView, proposal: ProposedSize) -> Size {
        Size.{ width = proposal.width ?? 0.0, height = proposal.height ?? 0.0 }
    }

    layout :: (self: *BoardView, bounds: Frame) {
        self.compute_layout(bounds);
    }

    render :: (self: *BoardView, ctx: *RenderContext, frame: Frame) {
        self.compute_layout(frame);

        // 1. Background image fills the whole view, behind the grid.
        if self.assets.bg_tex != 0 {
            ctx.add_image(frame, self.assets.bg_tex);
        }

        // 2. One cell tile per board cell, then its gem sampled by index column.
        gem_inset := self.cell_size * (1.0 - GEM_FILL_FRAC) * 0.5;
        gem_dim := self.cell_size * GEM_FILL_FRAC;
        for 0..BOARD_ROWS: (row) {
            for 0..BOARD_COLS: (col) {
                cf := self.cell_frame(col, row);

                if self.assets.cell_tex != 0 {
                    ctx.add_image(cf, self.assets.cell_tex);
                }

                g := self.board.at(col, row);
                if g != .empty and self.assets.gems_tex != 0 {
                    uv := self.assets.gem_uv(cast(s64) g);
                    gf := Frame.make(
                        cf.origin.x + gem_inset,
                        cf.origin.y + gem_inset,
                        gem_dim,
                        gem_dim
                    );
                    ctx.add_image_uv(gf, self.assets.gems_tex, uv.uv_min, uv.uv_max);
                }
            }
        }
    }

    handle_event :: (self: *BoardView, event: *Event, frame: Frame) -> bool {
        false
    }
}