#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include <errno.h>

#include "./assets/tsodinPog.c"
#include "./assets/tsodinCup.c"

#define NOB_IMPLEMENTATION
#define NOB_STRIP_PREFIX
#include "nob.h"

#define PI 3.14159265359

#define ARENA_IMPLEMENTATION
#include "./arena.h"

static Arena default_arena = {0};
static Arena *context_arena = &default_arena;

static void *context_alloc(size_t size)
{
    assert(context_arena);
    return arena_alloc(context_arena, size);
}

static void *context_realloc(void *oldp, size_t oldsz, size_t newsz)
{
    if (newsz <= oldsz) return oldp;
    return memcpy(context_alloc(newsz), oldp, oldsz);
}

#define STBI_MALLOC context_alloc
#define STBI_FREE UNUSED
#define STBI_REALLOC_SIZED context_realloc
#define STB_IMAGE_IMPLEMENTATION
#include "./stb_image.h"

#define STBIW_MALLOC STBI_MALLOC
#define STBIW_FREE STBI_FREE
#define STBIW_REALLOC_SIZED STBI_REALLOC_SIZED
#define STB_IMAGE_WRITE_IMPLEMENTATION
#include "./stb_image_write.h"

#define OLIVEC_IMPLEMENTATION
#include "olive.c"

#define BACKGROUND_COLOR 0xFF202020
#define FOREGROUND_COLOR 0xFF2020FF
#define WHITE_COLOR 0xFFAAAAAA
#define RED_COLOR 0xFF2020AA
#define GREEN_COLOR 0xFF20AA20
#define BLUE_COLOR 0xFFAA2020
#define ERROR_COLOR 0xFFFF00FF

#define TEST_DIR_PATH "./test"

bool canvas_stbi_load(const char *file_path, Olivec_Canvas *oc)
{
    int width, height;
    uint32_t *pixels = (uint32_t*) stbi_load(file_path, &width, &height, NULL, 4);
    if (pixels == NULL) return false;
    *oc = olivec_canvas(pixels, width, height, width);
    return true;
}

bool canvas_stbi_save(Olivec_Canvas oc, const char *file_path)
{
    return stbi_write_png(file_path, oc.width, oc.height, 4, oc.pixels, sizeof(uint32_t)*oc.stride);
}

typedef struct {
    Olivec_Canvas (*generate_actual_canvas)(void);
    const char *id;
    const char *expected_file_path;
    const char *actual_file_path;
    const char *diff_file_path;
} Test_Case;

#define DEFINE_TEST_CASE(name) \
    { \
        .generate_actual_canvas = test_##name, \
        .id = #name, \
        .expected_file_path = TEST_DIR_PATH "/" #name "_expected.png", \
        .actual_file_path = TEST_DIR_PATH "/" #name "_actual.png", \
        .diff_file_path = TEST_DIR_PATH "/" #name "_diff.png", \
    }

bool update_test_case(const Test_Case *tc)
{
    Olivec_Canvas actual_canvas = tc->generate_actual_canvas();
    const char *expected_file_path = tc->expected_file_path;

    if (!canvas_stbi_save(actual_canvas, expected_file_path)) {
        fprintf(stderr, "ERROR: could not write file %s: %s\n", expected_file_path, strerror(errno));
        return(false);
    }
    printf("%s: Generated %s\n", tc->id, expected_file_path);
    return(true);
}

Olivec_Canvas canvas_alloc(size_t width, size_t height)
{
    uint32_t *pixels = context_alloc(sizeof(uint32_t)*width*height);
    return olivec_canvas(pixels, width, height, width);
}

typedef enum {
    REPLAY_PASSED,
    REPLAY_FAILED,
    REPLAY_ERRORED,
} Replay_Result;

static inline size_t min_size(size_t a, size_t b)
{
    if (a < b) return a;
    return b;
}

static inline size_t max_size(size_t a, size_t b)
{
    if (a > b) return a;
    return b;
}

Replay_Result run_test_case(const char *program_path, const Test_Case *tc)
{
    printf("%s:", tc->id);
    fflush(stdout);

    const char *expected_file_path = tc->expected_file_path;
    const char *actual_file_path = tc->actual_file_path;
    const char *diff_file_path = tc->diff_file_path;

    Olivec_Canvas actual_canvas = tc->generate_actual_canvas();

    Olivec_Canvas expected_canvas;
    if (!canvas_stbi_load(expected_file_path, &expected_canvas)) {
        fprintf(stderr, "\n");
        fprintf(stderr, "  ERROR: could not read %s: %s\n", expected_file_path, stbi_failure_reason());
        if (errno == ENOENT) {
            fprintf(stderr, "  HINT: Consider running `$ %s update %s` to create it\n", program_path, tc->id);
        }
        return(REPLAY_ERRORED);
    }

    bool failed = false;

    if (expected_canvas.width != actual_canvas.width || expected_canvas.height != actual_canvas.height) {
        failed = true;
    }

    Olivec_Canvas diff_canvas =
        canvas_alloc(
            max_size(expected_canvas.width, actual_canvas.width),
            max_size(expected_canvas.height, actual_canvas.height));
    olivec_fill(diff_canvas, ERROR_COLOR);

    for (size_t y = 0; y < min_size(expected_canvas.height, actual_canvas.height); ++y) {
        for (size_t x = 0; x < min_size(expected_canvas.width, actual_canvas.width); ++x) {
            uint32_t expected_pixel = OLIVEC_PIXEL(expected_canvas, x, y);
            uint32_t actual_pixel = OLIVEC_PIXEL(actual_canvas, x, y);
            if (expected_pixel != actual_pixel) {
                OLIVEC_PIXEL(diff_canvas, x, y) = ERROR_COLOR;
                failed = true;
            } else {
                OLIVEC_PIXEL(diff_canvas, x, y) = expected_pixel;
            }
        }
    }

    if (failed) {
        fprintf(stderr, "\n");

        if (!canvas_stbi_save(actual_canvas, actual_file_path)) {
            fprintf(stderr, "  ERROR: could not write image file with actual pixels %s: %s\n", actual_file_path, strerror(errno));
            return(REPLAY_ERRORED);
        }

        if (!canvas_stbi_save(diff_canvas, diff_file_path)) {
            fprintf(stderr, "  ERROR: could not wrilte diff image file %s: %s\n", diff_file_path, strerror(errno));
            return(REPLAY_ERRORED);
        }

        fprintf(stderr, "  TEST FAILURE: unexpected pixels in generated image\n");
        fprintf(stderr, "    Expected: %s\n", expected_file_path);
        fprintf(stderr, "    Actual:   %s\n", actual_file_path);
        fprintf(stderr, "    Diff:     %s\n", diff_file_path);
        fprintf(stderr, "  HINT: If this behaviour is intentional confirm that by updating the image with `$ %s update`\n", program_path);
        return(REPLAY_FAILED);
    }

    printf(" OK\n");

    return(REPLAY_PASSED);
}

Olivec_Canvas test_fill_rect(void)
{
    size_t width = 128;
    size_t height = 128;
    Olivec_Canvas oc = canvas_alloc(width, height);
    olivec_fill(oc, BACKGROUND_COLOR);
    olivec_rect(oc, width/2 - width/8, height/2 - height/8, width/4, height/4, RED_COLOR);
    olivec_rect(oc, width - 1, height - 1, -width/2, -height/2, GREEN_COLOR);
    olivec_rect(oc, -width/4, -height/4, width/2, height/2, BLUE_COLOR);
    return oc;
}

Olivec_Canvas test_fill_circle(void)
{
    size_t width = 128;
    size_t height = 128;
    Olivec_Canvas oc = canvas_alloc(width, height);
    olivec_fill(oc, BACKGROUND_COLOR);
    olivec_circle(oc, 0, 0, width/2, RED_COLOR);
    olivec_circle(oc, width/2, height/2, width/4, BLUE_COLOR);
    olivec_circle(oc, width*3/4, height*3/4, -width/4, GREEN_COLOR);
    return oc;
}

Olivec_Canvas test_draw_line(void)
{
    size_t width = 128;
    size_t height = 128;
    Olivec_Canvas oc = canvas_alloc(width, height);
    olivec_fill(oc, BACKGROUND_COLOR);
    olivec_line(oc, 0, 0, width, height, RED_COLOR);
    olivec_line(oc, width, 0, 0, height, BLUE_COLOR);
    olivec_line(oc, width/2, 0, width/2, height, GREEN_COLOR);
    return oc;
}

Olivec_Canvas test_fill_triangle(void)
{
    size_t width = 128;
    size_t height = 128;
    Olivec_Canvas oc = canvas_alloc(width, height);

    olivec_fill(oc, BACKGROUND_COLOR);

    {
        int x1 = width/2,   y1 = height/8;
        int x2 = width/8,   y2 = height/2;
        int x3 = width*7/8, y3 = height*7/8;
        olivec_triangle(oc, x1, y1, x2, y2, x3, y3, RED_COLOR);
    }

    {
        int x1 = width/2,   y1 = height*2/8;
        int x2 = width*2/8, y2 = height/2;
        int x3 = width*6/8, y3 = height/2;
        olivec_triangle(oc, x1, y1, x2, y2, x3, y3, GREEN_COLOR);
    }

    {
        int x1 = width/8,   y1 = height/8;
        int x2 = width/8,   y2 = height*3/8;
        int x3 = width*3/8, y3 = height*3/8;
        olivec_triangle(oc, x1, y1, x2, y2, x3, y3, BLUE_COLOR);
    }

    return oc;
}

Olivec_Canvas test_alpha_blending(void)
{
    size_t width = 128;
    size_t height = 128;
    Olivec_Canvas oc = canvas_alloc(width, height);
    olivec_fill(oc, BACKGROUND_COLOR);
    olivec_rect(oc, 0, 0, width*3/4, height*3/4, RED_COLOR);
    olivec_rect(oc, width-1, height-1, -width*3/4, -height*3/4, 0x5520AA20);
    olivec_circle(oc, width/2, height/2, width/4, 0xBBAA2020);
    olivec_triangle(oc, 0, height-1, width-1, height-1, width/2, 0, 0xBB20AAAA);
    olivec_triangle3c(oc, 0, 0, width-1, 0, width/2, height-1, 0xBB2020AA, 0xBB20AA20, 0xBBAA2020);
    return oc;
}

Olivec_Canvas test_checker_example(void)
{
    int width = 800/2;
    int height = 600/2;
    int cols = (8*2);
    int rows = (6*2);
    int cell_width = (width/cols);
    int cell_height = (height/rows);
    Olivec_Canvas oc = canvas_alloc(width, height);

    olivec_fill(oc, BACKGROUND_COLOR);

    for (int y = 0; y < rows; ++y) {
        for (int x = 0; x < cols; ++x) {
            uint32_t color = BACKGROUND_COLOR;
            if ((x + y)%2 == 0) {
                color = 0xFF2020FF;
            }
            olivec_rect(oc, x*cell_width, y*cell_height, cell_width, cell_height, color);
        }
    }

    return oc;
}

Olivec_Canvas test_circle_example(void)
{
    int width = 800/2;
    int height = 600/2;
    int cols = (8*2);
    int rows = (6*2);
    int cell_width = (width/cols);
    int cell_height = (height/rows);
    Olivec_Canvas oc = canvas_alloc(width, height);
    olivec_fill(oc, BACKGROUND_COLOR);

    for (int y = 0; y < rows; ++y) {
        for (int x = 0; x < cols; ++x) {
            float u = (float)x/cols;
            float v = (float)y/rows;
            float t = (u + v)/2;

            int radius = cell_width;
            if (cell_height < radius) radius = cell_height;

            olivec_circle(oc,
                          x*cell_width + cell_width/2, y*cell_height + cell_height/2,
                          (size_t) (radius/8*(1 - t) + radius/2*t),
                          FOREGROUND_COLOR);
        }
    }

    return oc;
}

Olivec_Canvas test_lines_circle(void)
{
    int width = 800/2;
    int height = 600/2;
    Olivec_Canvas oc = canvas_alloc(width, height);
    olivec_fill(oc, BACKGROUND_COLOR);

    size_t n = 20;
    float angle = 2*PI/n;
    float length = width;
    if (length > height) length = height;
    length /= 3;
    float x1 = width/2;
    float y1 = height/2;
    for (size_t i = 0; i < n; ++i) {
        float x2 = x1 + cosf(angle*i)*length;
        float y2 = y1 + sinf(angle*i)*length;
        olivec_line(oc, x1, y1, x2, y2, 0xFF1818FF);
    }

    return oc;
}

Olivec_Canvas test_lines_example(void)
{
    int width = 800/2;
    int height = 600/2;
    Olivec_Canvas oc = canvas_alloc(width, height);

    olivec_fill(oc, BACKGROUND_COLOR);
    olivec_line(oc, 0, 0, width, height, FOREGROUND_COLOR);
    olivec_line(oc, width, 0, 0, height, FOREGROUND_COLOR);
    olivec_line(oc, 0, 0, width/4, height, 0xFF20FF20);
    olivec_line(oc, width/4, 0, 0, height, 0xFF20FF20);
    olivec_line(oc, width, 0, width/4*3, height, 0xFF20FF20);
    olivec_line(oc, width/4*3, 0, width, height, 0xFF20FF20);
    olivec_line(oc, 0, height/2, width, height/2, 0xFFFF3030);
    olivec_line(oc, width/2, 0, width/2, height, 0xFFFF3030);

    return oc;
}

Olivec_Canvas test_hello_world_text_rendering(void)
{
    size_t size = 5;
    const char *text = "hello, world";
    size_t text_len = strlen(text);
    Olivec_Canvas oc = canvas_alloc(400, 150);
    olivec_fill(oc, BACKGROUND_COLOR);
    olivec_text(oc, text, oc.width/2 - OLIVEC_DEFAULT_FONT_WIDTH*size*text_len/2, oc.height/2 - OLIVEC_DEFAULT_FONT_HEIGHT*size/2, olivec_default_font, size, FOREGROUND_COLOR);
    return oc;
}

Olivec_Canvas test_line_edge_cases(void)
{
    size_t width = 10;
    size_t height = 10;
    Olivec_Canvas oc = canvas_alloc(width, height);
    olivec_fill(oc, BACKGROUND_COLOR);
    // One pixel line
    olivec_line(oc, width/2, height/2, width/2, height/2, FOREGROUND_COLOR);
    // Out-of-bounds horizontally
    olivec_line(oc, width + 10, height/2, width + 20, height/2, FOREGROUND_COLOR);
    // Out-of-bounds vertically
    olivec_line(oc, width/2, height + 10, width/2, height + 20, FOREGROUND_COLOR);
    return oc;
}

Olivec_Canvas test_frame(void)
{
    size_t width = 256;
    size_t height = 128;
    Olivec_Canvas oc = canvas_alloc(width, height);
    olivec_fill(oc, BACKGROUND_COLOR);

    {
        size_t w = width/2;
        size_t h = height/2;
        olivec_frame(oc, 0, 0, w, h, 1, RED_COLOR);
    }

    {
        olivec_frame(oc, width/2, height/2, width, height, 1, GREEN_COLOR);
    }

    // Odd thiccness
    {
        size_t w = width/2;
        size_t h = height/2;
        size_t t = 5;
        olivec_frame(oc, width/2 - w/2, height/2 - h/2, w, h, t, WHITE_COLOR);
        olivec_frame(oc, width/2 - w/2, height/2 - h/2, w, h, 1, RED_COLOR);
    }

    // Even thiccness
    {
        size_t w = width/4 + 1;
        size_t h = height/4;
        size_t t = 6;
        olivec_frame(oc, width/2 - w/2, height/2 - h/2, w, h, t, WHITE_COLOR);
        olivec_frame(oc, width/2 - w/2, height/2 - h/2, w, h, 1, RED_COLOR);
    }

    // Zero thiccness
    {
        size_t w = width/8;
        size_t h = height/8;
        size_t t = 0;
        olivec_frame(oc, width/2 - w/2, height/2 - h/2, w, h, t, WHITE_COLOR);
    }

    return oc;
}

Olivec_Canvas test_sprite_blend(void)
{
    size_t width = 128;
    size_t height = 128;
    Olivec_Canvas dst = canvas_alloc(width, height);
    olivec_fill(dst, RED_COLOR);
    Olivec_Canvas src = canvas_alloc(width, height);

    for (size_t y = 0; y < src.height; ++y) {
        for (size_t x = 0; x < src.width; ++x) {
            if ((x + y)%2 == 0) {
                OLIVEC_PIXEL(src, x, y) = 0;
            } else {
                OLIVEC_PIXEL(src, x, y) = GREEN_COLOR;
            }
        }
    }

    olivec_sprite_blend(dst, 0, 0, width, height, src);

    return dst;
}

Olivec_Canvas test_sprite_blend_out_of_bounds_cut(void)
{
    size_t width = 128;
    size_t height = 128;
    Olivec_Canvas dst = canvas_alloc(width, height);
    Olivec_Canvas src = olivec_canvas(tsodinPog_pixels, tsodinPog_width, tsodinPog_height, tsodinPog_width);
    olivec_fill(dst, RED_COLOR);
    olivec_sprite_blend(dst, -width/2, -height/2, width, height, src);
    olivec_sprite_blend(dst, width/2, -height/2, width, height, src);
    olivec_sprite_blend(dst, -width/2, height/2, width, height, src);
    olivec_sprite_blend(dst, width/2, height/2, width, height, src);
    return dst;
}

Olivec_Canvas test_sprite_blend_flip(void)
{
    size_t width = 128;
    size_t height = 128;
    Olivec_Canvas dst = canvas_alloc(width, height);
    Olivec_Canvas src = olivec_canvas(tsodinPog_pixels, tsodinPog_width, tsodinPog_height, tsodinPog_width);
    olivec_fill(dst, RED_COLOR);
    olivec_sprite_blend(dst, 0, 0, width/2, height/2, src);
    olivec_sprite_blend(dst, width - 1, 0, -width/2, height/2, src);
    olivec_sprite_blend(dst, 0, height - 1, width/2, -height/2, src);
    olivec_sprite_blend(dst, width - 1, height - 1, -width/2, -height/2, src);
    return dst;
}

Olivec_Canvas test_sprite_blend_flip_cut(void)
{
    size_t width = 128;
    size_t height = 128;
    Olivec_Canvas dst = canvas_alloc(width, height);
    Olivec_Canvas src = olivec_canvas(tsodinPog_pixels, tsodinPog_width, tsodinPog_height, tsodinPog_width);
    olivec_fill(dst, RED_COLOR);
    olivec_sprite_blend(dst, -width/2, -height/2, width, height, src);
    olivec_sprite_blend(dst, width - 1 + width/2, -height/2, -width, height, src);
    olivec_sprite_blend(dst, -width/2, height - 1 + height/2, width, -height, src);
    olivec_sprite_blend(dst, width - 1 + width/2, height - 1 + height/2, -width, -height, src);
    return dst;
}

Olivec_Canvas test_empty_rect(void)
{
    size_t w = 8;
    size_t h = 8;
    Olivec_Canvas dst = canvas_alloc(w, h);
    olivec_fill(dst, BACKGROUND_COLOR);
    olivec_rect(dst, w/2, h/2, 0, 0, FOREGROUND_COLOR);
    return dst;
}

Olivec_Canvas test_sprite_blend_empty_rect(void)
{
    size_t w = 8;
    size_t h = 8;
    Olivec_Canvas dst = canvas_alloc(w, h);
    Olivec_Canvas src = olivec_canvas(tsodinPog_pixels, tsodinPog_width, tsodinPog_height, tsodinPog_width);
    olivec_fill(dst, BACKGROUND_COLOR);
    olivec_sprite_blend(dst, 0, 0, 0, 0, src);
    return dst;
}

Olivec_Canvas test_sprite_blend_null(void)
{
    size_t w = 8;
    size_t h = 8;
    Olivec_Canvas dst = canvas_alloc(w, h);
    olivec_fill(dst, BACKGROUND_COLOR);
    olivec_sprite_blend(dst, 0, 0, w, h, OLIVEC_CANVAS_NULL);
    return dst;
}

Olivec_Canvas test_sprite_blend_vs_copy(void)
{
    Olivec_Canvas tsodinCup = olivec_canvas(tsodinCup_pixels, tsodinCup_width, tsodinCup_height, tsodinCup_width);
    size_t w = tsodinCup.width;
    size_t h = tsodinCup.height*2;
    Olivec_Canvas dst = canvas_alloc(w, h);
    olivec_fill(dst, RED_COLOR);
    olivec_sprite_blend(dst, 0, 0, tsodinCup.width, tsodinCup.height, tsodinCup);
    olivec_sprite_copy(dst, 0, tsodinCup.height, tsodinCup.width, tsodinCup.height, tsodinCup);
    return dst;
}

Olivec_Canvas test_barycentric_overflow(void)
{
    size_t w = 256;
    size_t h = 256;
    Olivec_Canvas dst = canvas_alloc(w, h);
    olivec_fill(dst, 0xFF181818);
    olivec_triangle3c(dst, w/4, h/4, w/2, 0, 0, h, 0xFF0000FF, 0xFF00FF00, 0xFFFF0000);
    return dst;
}

Olivec_Canvas test_triangle_order_flip(void)
{
    size_t w = 256;
    size_t h = 256;
    Olivec_Canvas dst = canvas_alloc(w, h);
    olivec_fill(dst, 0xFF181818);
    olivec_triangle3c(
        dst,
        w/4, h/4,
        0, h,
        w, 0,
        0xFF00FF00,
        0xFFFF0000,
        0xFF0000FF);
    return dst;
}

Olivec_Canvas test_bilinear_interpolation(void)
{
    size_t factor = 2;
    Olivec_Canvas src = olivec_canvas(tsodinPog_pixels, tsodinPog_width, tsodinPog_height, tsodinPog_width);
    Olivec_Canvas dst = canvas_alloc(src.width*factor*2, src.height*factor);
    olivec_fill(dst, RED_COLOR);
    olivec_sprite_copy(dst, 0, 0, src.width*factor, src.height*factor, src);
    olivec_sprite_copy_bilinear(dst, src.width*factor, 0, src.width*factor, src.height*factor, src);
    return dst;
}

Olivec_Canvas test_fill_ellipse(void)
{
    size_t factor = 3;
    Olivec_Canvas dst = canvas_alloc(100*factor, 50*factor);
    olivec_fill(dst, BACKGROUND_COLOR);
    olivec_ellipse(dst, dst.width/2, dst.height/2, dst.width/3, dst.height/3, RED_COLOR);
    return dst;
}

Olivec_Canvas test_line_bug_offset(void)
{
    size_t factor = 3;
    size_t width = 100*factor;
    size_t height = 50*factor;
    Olivec_Canvas dst = canvas_alloc(width, height);
    olivec_fill(dst, BACKGROUND_COLOR);
    int x1 = 50;
    int y1 = 100;
    int x2 = 0;
    int y2 = -100;
    olivec_line(dst, x1, y1, x2, y2, GREEN_COLOR);
    olivec_circle(dst, x1, y1, 5, RED_COLOR);
    return dst;
}

Test_Case test_cases[] = {
    DEFINE_TEST_CASE(fill_rect),
    DEFINE_TEST_CASE(fill_circle),
    DEFINE_TEST_CASE(draw_line),
    DEFINE_TEST_CASE(fill_triangle),
    DEFINE_TEST_CASE(alpha_blending),
    DEFINE_TEST_CASE(checker_example),
    DEFINE_TEST_CASE(circle_example),
    DEFINE_TEST_CASE(lines_example),
    DEFINE_TEST_CASE(hello_world_text_rendering),
    DEFINE_TEST_CASE(lines_circle),
    DEFINE_TEST_CASE(line_edge_cases),
    DEFINE_TEST_CASE(frame),
    DEFINE_TEST_CASE(sprite_blend),
    DEFINE_TEST_CASE(sprite_blend_out_of_bounds_cut),
    DEFINE_TEST_CASE(sprite_blend_flip),
    DEFINE_TEST_CASE(sprite_blend_flip_cut),
    DEFINE_TEST_CASE(sprite_blend_empty_rect),
    DEFINE_TEST_CASE(empty_rect),
    DEFINE_TEST_CASE(sprite_blend_null),
    DEFINE_TEST_CASE(sprite_blend_vs_copy),
    DEFINE_TEST_CASE(triangle_order_flip),
    DEFINE_TEST_CASE(barycentric_overflow),
    DEFINE_TEST_CASE(bilinear_interpolation),
    DEFINE_TEST_CASE(fill_ellipse),
    DEFINE_TEST_CASE(line_bug_offset),
};
#define TEST_CASES_COUNT (sizeof(test_cases)/sizeof(test_cases[0]))

void list_available_tests(void)
{
    fprintf(stderr, "Available tests:\n");
    for (size_t i = 0; i < TEST_CASES_COUNT; ++i) {
        fprintf(stderr, "    %s\n", test_cases[i].id);
    }
}

Test_Case *find_test_case_by_id(const char *id)
{
    for (size_t i = 0; i < TEST_CASES_COUNT; ++i) {
        if (strcmp(test_cases[i].id, id) == 0) {
            return &test_cases[i];
        }
    }
    return NULL;
}
typedef struct {
    int (*run)(const char *program_path, int argc, char **argv);
    const char *id;
    const char *description;
} Subcmd;

void usage(const char *program_path);

int subcmd_run(const char *program_path, int argc, char **argv)
{
    if (argc <= 0) {
        for (size_t i = 0; i < TEST_CASES_COUNT; ++i) {
            if (run_test_case(program_path, &test_cases[i]) == REPLAY_ERRORED) return(1);
            arena_reset(&default_arena);
        }
    } else {
        const char *test_case_id = shift(argv, argc);
        Test_Case *tc = find_test_case_by_id(test_case_id);
        if (tc == NULL) {
            list_available_tests();
            fprintf(stderr, "ERROR: could not find test case `%s`\n", test_case_id);
            return(1);
        }

        if (run_test_case(program_path, tc) == REPLAY_ERRORED) return(1);
    }

    return 0;
}

int subcmd_update(const char *program_path, int argc, char **argv)
{
    UNUSED(program_path);

    if (argc <= 0) {
        for (size_t i = 0; i < TEST_CASES_COUNT; ++i) {
            if (!update_test_case(&test_cases[i])) return(1);
            arena_reset(&default_arena);
        }
    } else {
        const char *test_case_id = shift(argv, argc);
        Test_Case *tc = find_test_case_by_id(test_case_id);
        if (tc == NULL) {
            list_available_tests();
            fprintf(stderr, "ERROR: could not find test case `%s`\n", test_case_id);
            return(1);
        }

        if (!update_test_case(tc)) return(1);
    }

    return 0;
}

int subcmd_list(const char *program_path, int argc, char **argv)
{
    UNUSED(program_path);
    UNUSED(argc);
    UNUSED(argv);
    list_available_tests();
    return 0;
}

int subcmd_help(const char *program_path, int argc, char **argv)
{
    UNUSED(argc);
    UNUSED(argv);
    usage(program_path);
    return 0;
}

#define DEFINE_SUBCMD(name, desc) \
    { \
        .run = subcmd_##name, \
        .id = #name, \
        .description = desc, \
    }

Subcmd subcmds[] = {
    DEFINE_SUBCMD(run, "Run the tests"),
    DEFINE_SUBCMD(update, "Update the tests"),
    DEFINE_SUBCMD(list, "List all available tests"),
    DEFINE_SUBCMD(help, "Print this help message"),
};
#define SUBCMDS_COUNT (sizeof(subcmds)/sizeof(subcmds[0]))

Subcmd *find_subcmd_by_id(const char *id)
{
    for (size_t i = 0; i < SUBCMDS_COUNT; ++i) {
        if (strcmp(subcmds[i].id, id) == 0) {
            return &subcmds[i];
        }
    }
    return NULL;
}

void usage(const char *program_path)
{
    fprintf(stderr, "Usage: %s [Subcommand]\n", program_path);
    fprintf(stderr, "Subcommands:\n");

    int width = 0;
    for (size_t i = 0; i < SUBCMDS_COUNT; ++i) {
        int len = strlen(subcmds[i].id);
        if (width < len) width = len;
    }

    for (size_t i = 0; i < SUBCMDS_COUNT; ++i) {
        fprintf(stderr, "    %-*s - %s\n", width, subcmds[i].id, subcmds[i].description);
    }
}

int main(int argc, char **argv)
{
    int result = 0;

    {
        const char *program_path = shift(argv, argc);

        if (argc <= 0) {
            usage(program_path);
            fprintf(stderr, "ERROR: no subcommand is provided\n");
            return_defer(1);
        }

        const char *subcmd_id = shift(argv, argc);
        Subcmd *subcmd = find_subcmd_by_id(subcmd_id);
        if (subcmd != NULL) {
            return_defer(subcmd->run(program_path, argc, argv));
        } else {
            usage(program_path);
            fprintf(stderr, "ERROR: unknown subcommand `%s`\n", subcmd_id);
            return_defer(1);
        }
    }

defer:
    arena_free(&default_arena);
    return result;
}