#include "wapp.h"
#include "common.h"
#include "raylib.h"
#include <stdint.h>
#include <stdbool.h>
#include <assert.h>
#include <string.h>

enum EntityTag {
  ENTITY_TAG_MOVABLE    = 1 << 0,
  ENTITY_TAG_RENDERABLE = 1 << 1,
  ENTITY_TAG_COLLIDER   = 1 << 2,
};

typedef struct Entity Entity;
struct Entity {
  u16 id;
  u8  tag;
};

typedef struct Position Position;
struct Position {
  f32 x;
  f32 y;
};

typedef struct Scale Scale;
struct Scale {
  f32 width;
  f32 height;
};

typedef struct Velocity Velocity;
struct Velocity {
  f32 x;
  f32 y;
};

typedef struct Manager Manager;
struct Manager {
  Entity   *entities;
  Position *positions;
  Scale    *scales;
  Velocity *velocities;
  u64      count;
};

typedef void (*ScaleInitialiser)(Scale *scale, XOR256State *state);
typedef void (*VelocityInitialiser)(Velocity *velocity, XOR256State *state);
typedef void (*RaylibDrawRectFunc)(int posX, int posY, int width, int height, Color color);

void init_manager(const Allocator *allocator, Manager *manager);
void init_position(Position *position, XOR256State *state);
void init_scale_wanderer(Scale *scale, XOR256State *state);
void init_scale_zone(Scale *scale, XOR256State *state);
void init_velocity(Velocity *velocity, XOR256State *state);
void zero_velocity(Velocity *velocity, XOR256State *state);
void update_positions(Position *positions, Scale *scales, Velocity *velocities, u64 count);
void get_colliders();
void render_entities(const Entity *entities, const Position *positions, const Scale *scales, u64 count);
f32 get_random_float(XOR256State *state);

int main(void) {
  InitWindow(WIDTH, HEIGHT, "DOD test");
  SetTargetFPS(120);

  Allocator arena = wapp_mem_arena_allocator_init(MB(20));
  assert(!wapp_mem_allocator_invalid(&arena));

  XOR256State state = wapp_prng_xorshift_init_state();
  Manager manager   = {0};

  init_manager(&arena, &manager);

  ScaleInitialiser scale_initialisers[2]       = {init_scale_wanderer, init_scale_zone};
  VelocityInitialiser velocity_initialisers[2] = {init_velocity, zero_velocity};

  for (u64 i = 0; i < manager.count; ++i) {
    u8 is_zone = i < ZONE_COUNT;

    manager.entities[i].id  = i;
    manager.entities[i].tag = (ENTITY_TAG_COLLIDER & (is_zone << 2)) | ENTITY_TAG_MOVABLE;
#ifndef NDEBUG
    manager.entities[i].tag |= ENTITY_TAG_RENDERABLE;
#else
    manager.entities[i].tag |= ENTITY_TAG_RENDERABLE & ~(is_zone << 1);
#endif

    init_position(&(manager.positions[i]), &state);
    scale_initialisers[is_zone](&(manager.scales[i]), &state);
    velocity_initialisers[is_zone](&(manager.velocities[i]), &state);
  }

  while (!WindowShouldClose()) {
    f64 time = GetTime();
    if (time >= 20.0) {
      break;
    }

    update_positions(manager.positions, manager.scales, manager.velocities, manager.count);

    BeginDrawing();

    ClearBackground(BG_COLOR);

    render_entities(manager.entities, manager.positions, manager.scales, manager.count);

    DrawFPS(10, 10);

    EndDrawing();
  }

  wapp_mem_arena_allocator_destroy(&arena);

  CloseWindow();

  return 0;
}

void init_manager(const Allocator *allocator, Manager *manager) {
  assert(allocator != NULL && manager != NULL);

  u64 total_count      = (u64)WANDERER_COUNT + (u64)ZONE_COUNT;
  u64 entities_size    = sizeof(Entity)   * total_count;
  u64 positions_size   = sizeof(Position) * total_count;
  u64 scales_size      = sizeof(Scale)    * total_count;
  u64 velocities_size  = sizeof(Velocity) * total_count;
  u64 allocation_size  = entities_size + positions_size + scales_size + velocities_size;
  u8 *buffer           = wapp_mem_allocator_alloc(allocator, allocation_size);

  assert(buffer != NULL);

  memset(buffer, 0, allocation_size);

  manager->entities   = (Entity *)buffer;
  manager->positions  = (Position *)(buffer + entities_size);
  manager->scales     = (Scale *)(buffer + entities_size + positions_size);
  manager->velocities = (Velocity *)(buffer + entities_size + positions_size + scales_size);
  manager->count      = total_count;
}

void init_position(Position *position, XOR256State *state) {
  position->x = wapp_prng_xorshift_256(state) % WIDTH;
  position->y = wapp_prng_xorshift_256(state) % HEIGHT;
}

void init_scale_wanderer(Scale *scale, XOR256State *state) {
  f32 value = (f32)((wapp_prng_xorshift_256(state) % (MAX_WANDERER_DIM + 1 - MIN_WANDERER_DIM)) + MIN_WANDERER_DIM);
  scale->width  = value;
  scale->height = value;
}

void init_scale_zone(Scale *scale, XOR256State *state) {
  scale->width  = wapp_prng_xorshift_256(state) % ((u64)HALF_WIDTH - MIN_ZONE_DIM) + MIN_ZONE_DIM;
  scale->height = wapp_prng_xorshift_256(state) % ((u64)HALF_HEIGHT - MIN_ZONE_DIM) + MIN_ZONE_DIM;
}

void init_velocity(Velocity *velocity, XOR256State *state) {
  velocity->x = get_random_float(state);
  velocity->y = get_random_float(state);
}

void zero_velocity(Velocity *velocity, XOR256State *state) {
  velocity->x = 0.0f;
  velocity->y = 0.0f;
}

void update_positions(Position *positions, Scale *scales, Velocity *velocities, u64 count) {
  for (u64 i = 0; i < count; ++i) {
    positions[i].x += velocities[i].x;
    positions[i].y += velocities[i].y;

    f32 max_x = WIDTH - scales[i].width;
    f32 max_y = HEIGHT - scales[i].height;

    if (positions[i].x < 0 || positions[i].x >= max_x) {
      positions[i].x = min(max(positions[i].x, 0), max_x);
      velocities[i].x *= -1;
    }

    if (positions[i].y < 0 || positions[i].y >= max_y) {
      positions[i].y = min(max(positions[i].y, 0), max_y);
      velocities[i].y *= -1;
    }
  }
}

void render_entities(const Entity *entities, const Position *positions, const Scale *scales, u64 count) {
  persistent RaylibDrawRectFunc renderers[2] = {DrawRectangle, DrawRectangleLines};
  persistent Color colors[2]                 = {FG_COLOR, ZONE_COLOR};

  for (u64 i = 0; i < count; ++i) {
    u64 is_collider = (entities[i].tag & ENTITY_TAG_COLLIDER) == ENTITY_TAG_COLLIDER;

    renderers[is_collider](positions[i].x, positions[i].y, scales[i].width, scales[i].height, colors[is_collider]);
  }
}

f32 get_random_float(XOR256State *state) {
  i64 random = (i64)wapp_prng_xorshift_256(state) - INT64_MAX;
  return (f32)(random) / (f32)(INT64_MAX);
}