#include <SDL.h>
#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#include <SDL_ttf.h>
#include <SDL_mixer.h>
#include <stdlib.h>

/* 
 * Global Constants 
 * These define the window dimensions and are used for centering graphics.
 */
const int SCREEN_WIDTH = 800;
const int SCREEN_HEIGHT = 600;

/* 
 * Player Structure
 * Even if invisible, we keep the player state to allow for future gameplay logic.
 */
typedef struct {
    float x, y;
    float speed;
    int size;
    SDL_Color color;
} Player;

/*
 * Game State Structure
 * This is the 'Brain' of the game, containing everything needed to track the current session.
 */
typedef struct {
    bool is_running;            // Controls the main game loop
    // Message 1: "Hello, human."
    const char* message1;
    int visible_chars1;         // Number of characters revealed in message1
    uint32_t last_char_time1;   // Timestamp of last character revealed in message1
    // Message 2: "It is a known fact that C, is superior to every other programming language."
    const char* message2;
    int visible_chars2;         // Number of characters revealed in message2
    uint32_t last_char_time2;   // Timestamp of last character revealed in message2
    int message_stage;          // 0: showing message1, 1: showing message2
    uint32_t message1_finish_time; // Timestamp when message1 finished revealing (0 if not finished)
    // Escape key handling
    uint32_t escape_press_time; // Timestamp when Escape was first pressed (0 if not pressed)
    // Fonts
    TTF_Font* font_large;       // Font for message1 (120pt)
    TTF_Font* font_small;       // Font for message2 (24pt)
    TTF_Font* current_font;     // Currently used font (points to either font_large or font_small)
    // Audio
    Mix_Chunk* beep_chunk;      // Sound effect for each typed character
    // Screen shake effect
    float shake_timer;          // Time remaining for shake effect (ms)
    float shake_duration;       // Total duration of shake effect when triggered (ms)
    float shake_intensity;      // Current intensity of shake (pixels)
    Player player;              // The player object
} Game;

/**
 * Initializes SDL, TTF, and the game state.
 * Returns true if everything started correctly, false otherwise.
 */
bool init_game(Game *game) {
    // Initialize SDL Video subsystem
    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
        printf("SDL could not initialize! SDL_Error: %s\n", SDL_GetError());
        return false;
    }

    // Initialize SDL_ttf for text rendering
    if (TTF_Init() == -1) {
        printf("SDL_ttf could not initialize! TTF_Error: %s\n", TTF_GetError());
        return false;
    }

    // Initialize SDL_mixer for audio with lower frequency (22050 Hz) to lower pitch of beep
    if (Mix_OpenAudio(22050, MIX_DEFAULT_FORMAT, 2, 2048) < 0) {
        printf("SDL_mixer could not open audio! Mix_Error: %s\n", Mix_GetError());
        return false;
    }

    // Load the fonts
    game->font_large = TTF_OpenFont("assets/font.ttf", 120);
    if (!game->font_large) {
        printf("CRITICAL: Failed to load large font! TTF_Error: %s\n", TTF_GetError());
        return false;
    }
    game->font_small = TTF_OpenFont("assets/font.ttf", 24);
    if (!game->font_small) {
        printf("CRITICAL: Failed to load small font! TTF_Error: %s\n", TTF_GetError());
        return false;
    }
    game->current_font = game->font_large; // Start with large font for first message

    // Load the beep sound effect
    game->beep_chunk = Mix_LoadWAV("assets/dialog-beep.wav");
    if (!game->beep_chunk) {
        printf("WARNING: Failed to load beep sound! Mix_Error: %s\n", Mix_GetError());
        // Not critical, continue without sound
    }

    // Setup initial state
    game->is_running = true;
    game->escape_press_time = 0; // Not pressing escape initially
    game->message1 = "Hello, human.";
    game->visible_chars1 = 0;
    game->last_char_time1 = SDL_GetTicks();
    game->message2 = "This is the remake of the popular game\nUndertale, but rewritten and opensourced in\nthe best programming language known\nto man, C. Enjoy this peak of a GPL3.0 game :3";
    game->visible_chars2 = 0;
    game->last_char_time2 = 0; // Not used until we switch to message2
    game->message_stage = 0; // Start with message1
    game->message1_finish_time = 0; // Not finished yet
    // Initialize shake effect
    game->shake_timer = 0.0f;
    game->shake_duration = 300.0f; // 300ms shake duration
    game->shake_intensity = 0.0f;
    // Seed random number generator for shake effect
    srand((unsigned int)SDL_GetTicks());
    game->player = (Player){ .x = 100, .y = 100, .speed = 0.5f, .size = 32, .color = {255, 0, 0, 255} };

    return true;
}

/**
 * Processes keyboard and window events.
 * Handles the 'hold to quit' logic for the Escape key.
 */
void handle_input(Game *game, float delta_time) {
    SDL_Event event;
    while (SDL_PollEvent(&event)) {
        if (event.type == SDL_QUIT) {
            game->is_running = false;
        }
    }

    const uint8_t *state = SDL_GetKeyboardState(NULL);

    // ESCAPE KEY LOGIC:
    if (state[SDL_SCANCODE_ESCAPE]) {
        if (game->escape_press_time == 0) {
            // Just pressed
            game->escape_press_time = SDL_GetTicks();
        } else if (SDL_GetTicks() - game->escape_press_time >= 1000) {
            // Held for 1 second
            game->is_running = false;
        }
    } else {
        // Released
        game->escape_press_time = 0;
    }

    // Player Movement (Invisible for now)
    if (state[SDL_SCANCODE_UP])    game->player.y -= game->player.speed;
    if (state[SDL_SCANCODE_DOWN])  game->player.y += game->player.speed;
    if (state[SDL_SCANCODE_LEFT])   game->player.x -= game->player.speed;
    if (state[SDL_SCANCODE_RIGHT])  game->player.x += game->player.speed;
}

/**
 * Updates game logic independent of rendering.
 * Handles the typewriter timing.
 */
void update(Game *game) {
    // UPDATE SHAKE EFFECT:
    // Decrease shake timer and calculate current intensity
    if (game->shake_timer > 0.0f) {
        game->shake_timer -= 16.67f; // Approximate 60 FPS frame time
        if (game->shake_timer < 0.0f) game->shake_timer = 0.0f;
        // Calculate intensity based on remaining timer (linear fade out)
        game->shake_intensity = (game->shake_timer / game->shake_duration) * 4.0f; // Max 4px shake
    } else {
        game->shake_intensity = 0.0f;
    }

    // TYPEWRITER LOGIC:
    uint32_t current_time = SDL_GetTicks();

    if (game->message_stage == 0) {
        // Handling message1: "Hello, human."
        if (current_time - game->last_char_time1 >= 333) { // Adjusted timing
            if (game->visible_chars1 < (int)strlen(game->message1)) {
                char current_char = game->message1[game->visible_chars1];
                game->visible_chars1++;

                // Play beep for each character except spaces (already lower pitch due to mixer frequency)
                if (game->beep_chunk && current_char != ' ') {
                    Mix_PlayChannel(-1, game->beep_chunk, 0);
                    // Trigger shake effect for non-space characters
                    game->shake_timer = game->shake_duration;
                }
                game->last_char_time1 = current_time;
            }
            // Check if we just finished message1 (transition from not finished to finished)
            if (game->visible_chars1 == (int)strlen(game->message1) &&
                game->message1_finish_time == 0) {
                game->message1_finish_time = current_time;
            }
        }
    } else if (game->message_stage == 1) {
        // Handling message2: "It is a known fact that C, is superior to every other programming language."
        if (current_time - game->last_char_time2 >= 36) { // 1.66x faster timing for second message
            if (game->visible_chars2 < (int)strlen(game->message2)) {
                char current_char = game->message2[game->visible_chars2];
                game->visible_chars2++;

                // Play beep for each character except spaces (already lower pitch due to mixer frequency)
                if (game->beep_chunk && current_char != ' ') {
                    Mix_PlayChannel(-1, game->beep_chunk, 0);
                    // Trigger shake effect for non-space characters
                    game->shake_timer = game->shake_duration;
                }
                game->last_char_time2 = current_time;
            }
        }
    }

    // Check if we should switch to message2 (after 3.5 seconds of finishing message1)
    // This check happens regardless of which message we're currently displaying
    if (game->message_stage == 0 && game->message1_finish_time != 0 &&
        (current_time - game->message1_finish_time >= 3500)) {
        game->message_stage = 1;
        game->visible_chars2 = 0;
        game->last_char_time2 = current_time;
        game->current_font = game->font_small; // Switch to small font
    }

    // Keep player within screen bounds
    if (game->player.x < 0) game->player.x = 0;
    if (game->player.x > SCREEN_WIDTH - game->player.size) game->player.x = SCREEN_WIDTH - game->player.size;
    if (game->player.y < 0) game->player.y = 0;
    if (game->player.y > SCREEN_HEIGHT - game->player.size) game->player.y = SCREEN_HEIGHT - game->player.size;
}

/**
 * Handles all drawing operations.
 * Clears screen and renders centered text.
 */
void render(SDL_Renderer *renderer, Game *game) {
    // 1. Clear the screen to black
    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
    SDL_RenderClear(renderer);

    // 2. Render the revealed portion of the text
    if (game->current_font) {
        // Determine which message to render based on message_stage
        const char* message_to_render;
        int visible_chars_to_render;
        if (game->message_stage == 0) {
            message_to_render = game->message1;
            visible_chars_to_render = game->visible_chars1;
        } else {
            message_to_render = game->message2;
            visible_chars_to_render = game->visible_chars2;
        }

        if (visible_chars_to_render > 0) {
            SDL_Color white = {255, 255, 255, 255};
            int line_height = TTF_FontLineSkip(game->current_font);
            int line_count = 0;
            // First pass: count lines to compute total height
            int i = 0;
            while (i < visible_chars_to_render) {
                const char* line_start = message_to_render + i;
                // Find end of line (newline or end of visible chars)
                int line_len = 0;
                while (i + line_len < visible_chars_to_render && message_to_render[i + line_len] != '\n') {
                    line_len++;
                }
                line_count++;
                i += line_len;
                if (i < visible_chars_to_render && message_to_render[i] == '\n') {
                    i++; // skip newline
                }
            }
            // If no newline encountered, line_count is at least 1
            if (line_count == 0) line_count = 1;

            int total_height = line_count * line_height;
            int start_y = (SCREEN_HEIGHT - total_height) / 2;

            // Second pass: render each line
            i = 0;
            int line_y = 0;
            while (i < visible_chars_to_render) {
                const char* line_start = message_to_render + i;
                int line_len = 0;
                while (i + line_len < visible_chars_to_render && message_to_render[i + line_len] != '\n') {
                    line_len++;
                }
                // Create temporary buffer for this line
                char line_buf[256] = {0};
                strncpy(line_buf, line_start, line_len);
                line_buf[line_len] = '\0';

                SDL_Surface* surface = TTF_RenderText_Blended(game->current_font, line_buf, white);
                if (surface) {
                    SDL_Texture* texture = SDL_CreateTextureFromSurface(renderer, surface);
                    int shake_offset_x = (rand() % (int)(game->shake_intensity * 2 + 1)) - game->shake_intensity;
                    int shake_offset_y = (rand() % (int)(game->shake_intensity * 2 + 1)) - game->shake_intensity;
                    SDL_Rect text_rect = {
                        (SCREEN_WIDTH - surface->w) / 2 + shake_offset_x,
                        start_y + line_y + shake_offset_y,
                        surface->w,
                        surface->h
                    };
                    SDL_RenderCopy(renderer, texture, NULL, &text_rect);
                    SDL_FreeSurface(surface);
                    SDL_DestroyTexture(texture);
                }
                line_y += line_height;
                i += line_len;
                if (i < visible_chars_to_render && message_to_render[i] == '\n') {
                    i++; // skip newline
                }
            }
        }
    }

    // 3. Swap the backbuffer to the screen
    SDL_RenderPresent(renderer);
}

int main(int argc, char* args[]) {
    Game game;
    if (!init_game(&game)) return 1;

    SDL_Window *window = SDL_CreateWindow("C Game Template", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, SCREEN_WIDTH, SCREEN_HEIGHT, SDL_WINDOW_SHOWN);
    SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);

    // FPS Locking variables
    const int TARGET_FPS = 60;
    const uint32_t FRAME_DELAY = 1000 / TARGET_FPS;

    while (game.is_running) {
        uint32_t frame_start = SDL_GetTicks();

        // Calculate Delta Time (time since last frame) in milliseconds
        // Since we lock to 60FPS, this is usually around 16.6ms.
        float delta_time = 1000.0f / TARGET_FPS;

        handle_input(&game, delta_time);
        update(&game);
        render(renderer, &game);

        // FRAME CAPPER:
        // Calculate how long the frame took and sleep the remaining time.
        uint32_t frame_time = SDL_GetTicks() - frame_start;
        if (FRAME_DELAY > frame_time) {
            SDL_Delay(FRAME_DELAY - frame_time);
        }
    }

    // Cleanup memory
    if (game.font_large) TTF_CloseFont(game.font_large);
    if (game.font_small) TTF_CloseFont(game.font_small);
    if (game.beep_chunk) Mix_FreeChunk(game.beep_chunk);
    Mix_CloseAudio();
    Mix_Quit();
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    TTF_Quit();
    SDL_Quit();

    return 0;
}