/*
 * 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

// Entry list for display
#define MAX_ENTRIES 15
#define ENTRY_LENGTH 64
typedef struct {
    char entries[MAX_ENTRIES][ENTRY_LENGTH];
    int count;
} EntryList;
static EntryList g_entry_list = {{}, 0};
static bool g_force_full_refresh = false;  // Flag to force full refresh when list is full

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

// Display update message structure for inter-core communication
typedef struct {
    EntryList entries;
    bool use_partial;  // Use partial refresh instead of full refresh
    UWORD xstart;      // Partial refresh region
    UWORD ystart;
    UWORD xend;
    UWORD yend;
} 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_Clear();
    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 header
    EPD_7IN5B_V2_Init_Part();
    Paint_SelectImage(g_epd_red);
    printf("Drawing header\r\n");
    Paint_DrawString_EN(10, 10, "What's new today:", &Font24, WHITE, RED);
    
    // Display the image with both black and red buffers
    // printf("display text\r\n");
    EPD_7IN5B_V2_Display_Partial(g_epd_red, 0, 0, EPD_7IN5B_V2_WIDTH, EPD_7IN5B_V2_HEIGHT);
    // printf("delay\r\n");
    // DEV_Delay_ms(1000);
    
    printf("e-Paper display ready!\r\n");
    // EPD_7IN5B_V2_Sleep();
}

// 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

/**
 * Add an entry to the display list and send update to core 1
 */
void send_display_update(const char *entry) {
    if (!g_display_ready) return;  // Don't send if display isn't ready
    
    // Check if list is at capacity
    if (g_entry_list.count >= MAX_ENTRIES) {
        // List is full - clear all entries and start fresh
        printf("[Core 0] List is FULL - clearing all entries and starting fresh\n");
        g_entry_list.count = 0;
        g_force_full_refresh = true;
    }
    
    // Add entry to global list
    strncpy(g_entry_list.entries[g_entry_list.count], entry, ENTRY_LENGTH - 1);
    g_entry_list.entries[g_entry_list.count][ENTRY_LENGTH - 1] = '\0';
    g_entry_list.count++;
    
    // Allocate message structure
    DisplayMessage *msg = (DisplayMessage *)malloc(sizeof(DisplayMessage));
    if (msg == NULL) {
        printf("Failed to allocate display message!\n");
        return;
    }
    
    // Copy entry list to message
    msg->entries = g_entry_list;
    
    // Decide whether to use partial or full refresh
    msg->use_partial = !g_force_full_refresh;
    
    if (g_force_full_refresh) {
        printf("[Core 0] Forcing full refresh this update\n");
        g_force_full_refresh = false;  // Reset flag after setting it in message
    }
    
    // Setup partial refresh region (text area at top of display)
    msg->xstart = 0;
    msg->ystart = 50;      // Start below the header
    msg->xend = 800;       // Full width
    msg->yend = 480;       // Full height from header onwards
    
    // 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");
    
    // Initialize for partial refresh on second call
    EPD_7IN5B_V2_Init_Part();
    
    // 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 with %d entries\n", msg->entries.count);
            
            // 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 partial refresh, only clear the text area
                UWORD width = (EPD_7IN5B_V2_WIDTH / 8);
                UWORD y_start = msg->ystart;
                UWORD y_end = msg->yend;
                
                Paint_SelectImage(g_epd_image);
                Paint_Clear(WHITE);
                if(!msg->use_partial){
                    // for loop 5 times display white partial
                    int i = 0;
                    for(i = 0; i < 1; i++){
                        EPD_7IN5B_V2_Display_Partial(g_epd_image, msg->xstart, msg->ystart, msg->xend, msg->yend);
                    }
                }
                
                // Draw all entries starting below header
                UWORD y_pos = 0;
                /*for (int i = 0; i < msg->entries.count; i++) {
                    if (y_pos + 20 < 480) {  // Don't draw beyond screen
                        Paint_DrawString_EN(20, y_pos, msg->entries.entries[i], &Font16, WHITE, BLACK);
                        y_pos += 25;  // Space between entries
                    }
                }*/
                // paint only the last 3 entries
                int start_index = msg->entries.count > 2 ? msg->entries.count - 2 : 0;
                for (int i = start_index; i < msg->entries.count; i++) {
                    if (y_pos + 25 < 480) {  //Don't draw beyond screen
                        Paint_DrawString_EN(20, i*25, msg->entries.entries[i], &Font16, WHITE, BLACK);
                        y_pos += 25;  // Space between entries
                    } else {
                        printf("Skipping entry to avoid overflow\n");
                    }
                }
                // Use partial or full refresh
                //if (msg->use_partial) {
                    printf("[Core 1] Using partial refresh\n");
                    EPD_7IN5B_V2_Display_Partial(g_epd_image, msg->xstart, msg->ystart, msg->xend, msg->yend);
                /*} else {
                    printf("[Core 1] Using full refresh\n");
                    // EPD_7IN5B_V2_Init();
                    // EPD_7IN5B_V2_Clear();
                    // DEV_Delay_ms(500);
                    
                    // Re-initialize partial refresh mode after full refresh
                    printf("[Core 1] Reinitializing partial refresh mode\n");
                    EPD_7IN5B_V2_Init_Part();
                    Paint_SelectImage(g_epd_image);
                    EPD_7IN5B_V2_Display_Partial(g_epd_image, msg->xstart, msg->ystart, msg->xend, msg->yend);
                }*/
            }
            
            // 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;
}