#ifndef GBAEXP_TILES_H
#define GBAEXP_TILES_H

#include <stdarg.h>

#include "common.h"
#include "bd-font.c"

typedef struct TextEngine {
    // Currently working on tiled backgrounds only. The X and Y positions
    // correspond to the tile X and Y starting from the top left of the screen.
    // For a 240x160 screen, we have 30x20 tiles available.
    size_t cursor_x;
    size_t cursor_y;
    // Pointer to the screenblock being used for writing to the screen.
    u16 *screenblock;
} TextEngine;

static TextEngine text_engine = {0};

void
txt_putc(char c) {
    if (c == '\0') {
        return;
    }
    if (c == '\n') {
        text_engine.cursor_x = 0;
        text_engine.cursor_y++;
    } else {
        text_engine.screenblock[text_engine.cursor_x + 32 * text_engine.cursor_y] = c;
        text_engine.cursor_x++;
        if (text_engine.cursor_x >= 30) {
            text_engine.cursor_x = 0;
            text_engine.cursor_y++;
        }
    }
    if (text_engine.cursor_y >= 20) {
        text_engine.cursor_y = 0;
    }
}

static inline void
txt_puts(char *msg) {
    while (*msg) {
        txt_putc(*msg++);
    }
}

void
txt_init(size_t bg, Color clr, size_t cb_idx) {
    // The screenblock for the tile map should start after the tile memory
    // (MEM_VRAM + 0x2000 for 256 characters). Since each screenblock is
    // composed of 1024 screenblock entries of u16 (2 bytes), we need an
    // screenblock index offset of 8192 / (1024 * 2) = 4 screen blocks.
    size_t sb_idx = cb_idx * 8 + 4;

    // Set the background parameters for the text layer.
    BG_CTRL(bg) = BG_CHARBLOCK(cb_idx) | BG_SCREENBLOCK(sb_idx) | BG_PRIORITY(3);

    // Load font data in video memory. Each character is unpacked into a tile of
    // 8 32bit values (4bpp), meaning that for the full ASCII set of 256
    // characters, we need 8192 bytes of VRAM (8 * 4 * 256).
    unpack_tiles(&bd_font, &CHARBLOCK_MEM[cb_idx], 256);

    // Load palette color.
    PAL_BUFFER_BG[1] = clr;

    // Update text_engine variables.
    text_engine.screenblock = SCREENBLOCK_MEM[sb_idx];
}

// Print text to the screen with formatting.
void
txt_printf(char *msg, ...) {
    va_list arg_list;
    va_start(arg_list, msg);
    char c;
    char prev_c;
    while ((c = *msg++) != '\0') {
        if (c != '%') {
            txt_putc(c);
            prev_c = c;
            continue;
        }
        c = *msg++;
        switch (c) {
            case 's': {
                txt_puts(va_arg(arg_list, char *));
            } break;
            case 'd': {
                char buf[32] = {0};
                int x = va_arg(arg_list, int);
                sprintf(buf, "%d", x);
                txt_puts(buf);
            } break;
            case 'u': {
                char buf[32] = {0};
                unsigned int x = va_arg(arg_list, unsigned int);
                sprintf(buf, "%u", x);
                txt_puts(buf);
            } break;
            case 'x': {
                char buf[32] = {0};
                unsigned int x = va_arg(arg_list, unsigned int);
                sprintf(buf, "%x", x);
                txt_puts(buf);
            } break;
            default: {
                txt_putc('%');
                txt_putc(c);
            } break;
        }
    }
}

void
txt_clear_line(void) {
    for (size_t i = 0; i < 30; ++i) {
        text_engine.screenblock[i + 32 * text_engine.cursor_y] = ' ';
    }
    text_engine.cursor_x = 0;
}

void
txt_clear_screen(void) {
    for (size_t j = 0; j < 20; ++j) {
        for (size_t i = 0; i < 30; ++i) {
            text_engine.screenblock[i + 32 * j] = ' ';
        }
    }
    text_engine.cursor_x = 0;
    text_engine.cursor_y = 0;
}

void
txt_position(size_t tile_x, size_t tile_y) {
    text_engine.cursor_x = tile_x;
    text_engine.cursor_y = tile_y;
}

#endif // GBAEXP_TILES_H