#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>

#include "lvgl.h"
#include "esp_lvgl_port.h"

#include "lcd/ui_log.h"
#include "lcd/ui_internal.h"

#define UI_LOG_MAX_LINES 41
#define UI_LOG_LINE_MAX_LENGTH 160

static lv_obj_t *log_textarea = NULL;
static char log_lines[UI_LOG_MAX_LINES][UI_LOG_LINE_MAX_LENGTH];
static size_t log_line_length = 0;
static size_t log_line_start = 0;

static size_t ui_log_buffer_index(size_t line_offset){
    return (log_line_start + line_offset) % UI_LOG_MAX_LINES;
}

// Stores text in the ring buffer, sets *out_evicted when the oldest line had to
// be dropped, and returns the stored (possibly truncated) line.
static const char *ui_log_store_line(const char *text, bool *out_evicted){
    size_t line_index;
    bool evicted = false;

    if(log_line_length < UI_LOG_MAX_LINES){
        line_index = ui_log_buffer_index(log_line_length);
        log_line_length++;
    }
    else{
        line_index = log_line_start;
        log_line_start = ui_log_buffer_index(1);
        evicted = true;
    }

    snprintf(log_lines[line_index], sizeof(log_lines[line_index]), "%s", text);
    *out_evicted = evicted;
    return log_lines[line_index];
}

static void ui_log_append_line_locked(const char *line){
    lv_textarea_add_text(log_textarea, line);
    lv_textarea_add_text(log_textarea, "\n");
    lv_textarea_set_cursor_pos(log_textarea, LV_TEXTAREA_CURSOR_LAST);
}

static void ui_log_render_all_locked(void){
    lv_textarea_set_text(log_textarea, "");
    for(size_t line_offset = 0; line_offset < log_line_length; line_offset++){
        lv_textarea_add_text(log_textarea, log_lines[ui_log_buffer_index(line_offset)]);
        lv_textarea_add_text(log_textarea, "\n");
    }
    lv_textarea_set_cursor_pos(log_textarea, LV_TEXTAREA_CURSOR_LAST);
}

void ui_log_append(const char *text){
    if(text == NULL) return;

    bool evicted = false;
    const char *stored_line = ui_log_store_line(text, &evicted);
    if(log_textarea == NULL) return;

    lvgl_port_lock(0);
    // Appending a line is O(1); only a dropped oldest line forces a full rebuild.
    if(evicted) ui_log_render_all_locked();
    else ui_log_append_line_locked(stored_line);
    lvgl_port_unlock();
}

void ui_log_appendf(const char *format, ...){
    if(format == NULL) return;

    char line[UI_LOG_LINE_MAX_LENGTH];
    va_list args;
    va_start(args, format);
    vsnprintf(line, sizeof(line), format, args);
    va_end(args);

    ui_log_append(line);
}

void ui_log_detach(void){
    log_textarea = NULL;
}

void ui_log_build_view(lv_obj_t *screen){
    ui_attach_toggle(screen);
    lv_obj_set_style_bg_color(screen, lv_color_hex(0x101418), 0);

    lv_obj_t *title = lv_label_create(screen);
    ui_attach_toggle(title);
    lv_label_set_text(title, "SD Image Viewer by Timo Niemann");
    lv_obj_set_style_text_color(title, lv_color_white(), 0);
    lv_obj_align(title, LV_ALIGN_TOP_MID, 0, 14);

    log_textarea = lv_textarea_create(screen);
    ui_attach_toggle(log_textarea);
    lv_obj_set_size(log_textarea, 440, 730);
    lv_obj_align(log_textarea, LV_ALIGN_TOP_LEFT, 20, 40);
    lv_textarea_set_one_line(log_textarea, false);
    lv_textarea_set_cursor_click_pos(log_textarea, false);
    lv_textarea_set_text(log_textarea, "");
    lv_obj_set_style_bg_color(log_textarea, lv_color_hex(0x182028), 0);
    lv_obj_set_style_text_color(log_textarea, lv_color_hex(0xdde7ef), 0);
    lv_obj_set_style_border_color(log_textarea, lv_color_hex(0x4b6478), 0);
    lv_obj_set_style_radius(log_textarea, 4, 0);
    lv_obj_set_style_pad_all(log_textarea, 12, 0);

    ui_log_render_all_locked();
}