/*
 * Simple USB Serial Echo Program with Timeout, Reconnect, and Backspace Logic.
 * Converted to C++ so the project can use the `pico-ssd1306` C++ library.
 * Integrated with e-ink display support via Pico_ePaper library.
 */

#include "pico/stdlib.h"
#include "pico/time.h" // Needed for time_us_64()
#include "pico/multicore.h"
#include <stdio.h>
#include <ctype.h>
#include <cstring>
#include <stdlib.h>

#include "display.h"
#include "commands/echo.h"

// e-Paper library includes
extern "C" {
    #include "DEV_Config.h"
    #include "EPD_7in5b_V2.h"
    #include "GUI_Paint.h"
}

// Holds last echoed line for display
static char g_last_echo[128] = "";

// e-Paper display buffers
static UBYTE *g_epd_image = NULL;  // Black image buffer
static UBYTE *g_epd_red = NULL;    // Red image buffer

// Synchronization flag for multicore initialization
static volatile bool g_display_ready = false;

// Display update message structure for inter-core communication
typedef struct {
    char line1[64];
    char line2[64];
} DisplayMessage;

void init_epaper_display() {
    printf("Initializing 7.5\" e-Paper display (B V2)...\r\n");
    
    // Initialize the hardware
    if (DEV_Module_Init() != 0) {
        printf("Failed to initialize e-Paper hardware!\r\n");
        return;
    }
    
    // Initialize the display
    printf("EPD_7IN5B_V2_Init()\r\n");
    EPD_7IN5B_V2_Init_Fast();
    printf("EPD_7IN5B_V2_Clear()\r\n");
    EPD_7IN5B_V2_ClearBlack();
    DEV_Delay_ms(500);
    
    // Create image buffers for black and red content
    // 7.5" display: 800x480, 8 pixels per byte, so (800/8) * 480 = 48000 bytes each
    UWORD imagesize = (EPD_7IN5B_V2_WIDTH / 8) * EPD_7IN5B_V2_HEIGHT;
    
    g_epd_image = (UBYTE *)malloc(imagesize);
    g_epd_red = (UBYTE *)malloc(imagesize);
    
    if (g_epd_image == NULL || g_epd_red == NULL) {
        printf("Failed to allocate memory for e-Paper image buffers!\r\n");
        return;
    }
    
    // Initialize red buffer to all white (0xFF = no red pixels)
    for (UWORD i = 0; i < imagesize; i++) {
        g_epd_red[i] = 0xFF;
    }
    
    // Setup paint buffer for black content
    printf("White background\r\n");
    Paint_NewImage(g_epd_image, EPD_7IN5B_V2_WIDTH, EPD_7IN5B_V2_HEIGHT, 0, WHITE);
    Paint_SelectImage(g_epd_image);
    Paint_Clear(WHITE);
    
    // Draw "Hello World" on the display
    printf("Drawing\r\n");
    Paint_DrawString_EN(10, 10, "Hello World!", &Font24, WHITE, BLACK);
    Paint_DrawString_EN(10, 60, "7.5\" e-Paper Initialized", &Font16, WHITE, BLACK);
    
    // Display the image with both black and red buffers
    printf("display text\r\n");
    EPD_7IN5B_V2_Display(g_epd_image, g_epd_red);
    printf("delay\r\n");
    DEV_Delay_ms(2000);
    
    printf("e-Paper display ready!\r\n");
    // EPD_7IN5B_V2_Sleep();
}

void update_epaper_display(const char *line1, const char *line2) {
    if (g_epd_image == NULL || g_epd_red == NULL) return;
    
    // Clear and prepare buffers
    UWORD imagesize = (EPD_7IN5B_V2_WIDTH / 8) * EPD_7IN5B_V2_HEIGHT;
    for (UWORD i = 0; i < imagesize; i++) {
        g_epd_red[i] = 0xFF;  // No red pixels
    }
    
    Paint_SelectImage(g_epd_image);
    Paint_Clear(WHITE);
    
    if (line1) {
        Paint_DrawString_EN(50, 100, (char *)line1, &Font16, BLACK, WHITE);
    }
    if (line2) {
        Paint_DrawString_EN(50, 150, (char *)line2, &Font16, BLACK, WHITE);
    }
    
    EPD_7IN5B_V2_Display(g_epd_image, g_epd_red);
}

// Define the maximum size for the input string buffer
#define MAX_INPUT_LEN 64
// Define the timeout period: 5 seconds in microseconds
#define TIMEOUT_US 5000000
// ASCII code for Backspace (often sent as 0x08)
#define ASCII_BACKSPACE 8

/**
 * Send a display update message to core 1 via FIFO
 */
void send_display_update(const char *line1, const char *line2) {
    if (!g_display_ready) return;  // Don't send if display isn't ready
    
    // Allocate message structure
    DisplayMessage *msg = (DisplayMessage *)malloc(sizeof(DisplayMessage));
    if (msg == NULL) {
        printf("Failed to allocate display message!\n");
        return;
    }
    
    // Copy strings into message
    strncpy(msg->line1, line1 ? line1 : "", sizeof(msg->line1) - 1);
    msg->line1[sizeof(msg->line1) - 1] = '\0';
    
    strncpy(msg->line2, line2 ? line2 : "", sizeof(msg->line2) - 1);
    msg->line2[sizeof(msg->line2) - 1] = '\0';
    
    // Send message pointer to core 1
    multicore_fifo_push_blocking((uint32_t)msg);
    
    // Wait for core 1 to complete the update
    // multicore_fifo_pop_blocking();
}

/**
 * Core 1 function: Runs display initialization and update handling
 */
void core1_display_init() {
    init_epaper_display();
    g_display_ready = true;
    
    printf("[Core 1] Display ready, waiting for update messages...\n");
    
    // Core 1 main loop: handle display updates via FIFO
    while (true) {
        // Check if there's a message from core 0
        if (multicore_fifo_rvalid()) {
            // Read the message pointer
            uint32_t msg_addr = multicore_fifo_pop_blocking();
            DisplayMessage *msg = (DisplayMessage *)msg_addr;
            
            printf("[Core 1] Updating display: '%s' / '%s'\n", msg->line1, msg->line2);
            
            // Update the e-Paper display
            if (g_epd_image != NULL && g_epd_red != NULL) {
                UWORD imagesize = (EPD_7IN5B_V2_WIDTH / 8) * EPD_7IN5B_V2_HEIGHT;
                for (UWORD i = 0; i < imagesize; i++) {
                    g_epd_red[i] = 0xFF;
                }
                
                // Paint_SelectImage(g_epd_image);
                // Paint_Clear(WHITE);
                
                if (msg->line1[0] != '\0') {
                    Paint_DrawString_EN(50, 100, msg->line1, &Font16, BLACK, WHITE);
                }
                if (msg->line2[0] != '\0') {
                    Paint_DrawString_EN(50, 150, msg->line2, &Font16, BLACK, WHITE);
                }
                
                EPD_7IN5B_V2_Display(g_epd_image, g_epd_red);
            }
            
            // Free the message (it was allocated by core 0)
            free(msg);
            
            // Signal back to core 0 that update is complete
            multicore_fifo_push_blocking(1);
        }
        
        sleep_ms(10);
    }
}

void wait_for_usb_connection(DisplayManager &display) {
    printf("Waiting for USB host to connect...\n");
    while (!stdio_usb_connected()) {
        sleep_ms(100);
    }
    printf("\nConnection Established! Starting Echo Session...\n");
    display.refresh(">", nullptr);
}

void run_echo_session(DisplayManager &display) {
    char input_buffer[MAX_INPUT_LEN];
    int buffer_index = 0;

    printf("--- Welcome User! ---\n");
    printf("Type a command (or write help):\n");
    printf("--------------------------------------------\n");
    printf("> ");

    while (stdio_usb_connected()) {
        int c = getchar_timeout_us(0);
        if (c != PICO_ERROR_TIMEOUT) {
            char input_char = (char)c;
            if (input_char == ASCII_BACKSPACE || input_char == 127) {
                if (buffer_index > 0) {
                    buffer_index--;
                    printf("\b \b");
                    // update displays to reflect removed char
                    input_buffer[buffer_index] = '\0';
                    display.refresh(input_buffer, g_last_echo);
                    // send_display_update(input_buffer, g_last_echo);
                }
            } else if (input_char == '\r' || input_char == '\n') {
                echo_and_reset(input_buffer, &buffer_index);
                // Save last echoed (all caps) for display
                size_t i = 0;
                for (; input_buffer[i] != '\0' && i < sizeof(g_last_echo) - 1; ++i) {
                    g_last_echo[i] = input_buffer[i];
                }
                g_last_echo[i] = '\0';
                // Update both displays to show cleared input and last echo
                display.set_last_echo(g_last_echo);
                display.refresh("", g_last_echo);
                send_display_update("", g_last_echo);
            } else if (buffer_index < (MAX_INPUT_LEN - 1) && isprint(input_char)) {
                printf("%c", input_char);
                input_buffer[buffer_index] = input_char;
                buffer_index++;
                // update both displays with current input
                input_buffer[buffer_index] = '\0';
                display.refresh(input_buffer, g_last_echo);
                // send_display_update(input_buffer, g_last_echo);
            }
        }
        sleep_us(100);
    }
    
    printf("\nHost disconnected. Ending Echo Session.\n");
}

int main() {
    stdio_init_all();
    // Launch display initialization on core 1
    printf("Launching e-Paper display init on core 1...\n");
    multicore_launch_core1(core1_display_init);
    
    DisplayManager display;
    display.init();
    display.refresh("Waiting for USB/Serial", nullptr);

    while (true) {
        wait_for_usb_connection(display);
        run_echo_session(display);
    }

    return 0;
}