/**
 * @file ui_status.c
 * @brief Standalone LCD/button frontend for profile-driven operation.
 *
 * Architectural note:
 * This service owns all user-facing status formatting and button debouncing.
 * The application core pushes state into this module, while this module
 * returns high-level events such as "select next profile".
 */

#include "ui_status.h"

#include <stdbool.h>
#include <stdio.h>
#include <string.h>

#include "board_io.h"
#include "lcd1602_display.h"

#define UI_STATUS_LCD_COLUMNS 16u
#define UI_STATUS_BUTTON_DEBOUNCE_TICKS_10MS 3u

typedef struct ui_button_state_t {
    bool raw_pressed;
    bool stable_pressed;
    uint32_t last_change_tick_10ms;
} ui_button_state_t;

static char g_profile_name[APP_PROFILE_NAME_LENGTH];
static app_mode_t g_mode = APP_MODE_IDLE;
static uint8_t g_error_flags = 0u;
static uint8_t g_initialised = 0u;
static uint8_t g_display_dirty = 0u;
static ui_button_state_t g_button = {false, false, 0u};

static void ui_status_mark_dirty(void);
static void ui_status_copy_padded(char *destination, const char *source);
static const char *ui_status_mode_name(app_mode_t mode);
static void ui_status_build_line_1(char *line_buffer);
static void ui_status_build_line_2(char *line_buffer);
static void ui_status_refresh_display(void);

void ui_status_init(void)
{
    bool raw_pressed;

    memset(g_profile_name, 0, sizeof(g_profile_name));
    g_mode = APP_MODE_IDLE;
    g_error_flags = 0u;

    board_io_init_standalone_ui();
    raw_pressed = board_io_is_standalone_ui_button_pressed();

    /*
     * Synchronise the debounce state with the physical input level at boot.
     * This prevents a stuck-low or already-held button from generating a
     * synthetic "next profile" event immediately after startup.
     */
    g_button.raw_pressed = raw_pressed;
    g_button.stable_pressed = raw_pressed;
    g_button.last_change_tick_10ms = 0u;

    lcd1602_display_init();

    g_initialised = 1u;
    g_display_dirty = 1u;
    ui_status_refresh_display();
}

void ui_status_set_profile_name(const char *profile_name)
{
    char next_name[APP_PROFILE_NAME_LENGTH] = {0};

    if (profile_name != NULL)
    {
        strncpy(next_name, profile_name, sizeof(next_name) - 1u);
    }

    if (strncmp(g_profile_name, next_name, sizeof(g_profile_name)) != 0)
    {
        memcpy(g_profile_name, next_name, sizeof(g_profile_name));
        ui_status_mark_dirty();
    }
}

void ui_status_set_mode(app_mode_t mode)
{
    /*
     * TX_CURRENT is a transient transport state rather than a user-visible
     * operating mode. Ignoring it prevents needless LCD churn during polling.
     */
    if (mode == APP_MODE_TX_CURRENT)
    {
        return;
    }

    if (g_mode != mode)
    {
        g_mode = mode;
        ui_status_mark_dirty();
    }
}

void ui_status_set_error(uint8_t error_flags)
{
    if (g_error_flags != error_flags)
    {
        g_error_flags = error_flags;
        ui_status_mark_dirty();
    }
}

app_event_t ui_status_poll_event(uint32_t tick_10ms)
{
    bool raw_pressed;
    app_event_t event = APP_EVENT_NONE;

    if (g_initialised == 0u)
    {
        return APP_EVENT_NONE;
    }

    raw_pressed = board_io_is_standalone_ui_button_pressed();

    if (raw_pressed != g_button.raw_pressed)
    {
        g_button.raw_pressed = raw_pressed;
        g_button.last_change_tick_10ms = tick_10ms;
    }
    else if ((tick_10ms - g_button.last_change_tick_10ms) >= UI_STATUS_BUTTON_DEBOUNCE_TICKS_10MS)
    {
        if (g_button.stable_pressed != g_button.raw_pressed)
        {
            g_button.stable_pressed = g_button.raw_pressed;
            if (g_button.stable_pressed)
            {
                event = APP_EVENT_PROFILE_NEXT;
            }
        }
    }

    if (g_display_dirty != 0u)
    {
        ui_status_refresh_display();
    }

    return event;
}

static void ui_status_mark_dirty(void)
{
    g_display_dirty = 1u;
}

static void ui_status_copy_padded(char *destination, const char *source)
{
    size_t index;

    for (index = 0u; index < UI_STATUS_LCD_COLUMNS; ++index)
    {
        destination[index] = ' ';
    }
    destination[UI_STATUS_LCD_COLUMNS] = '\0';

    if (source == NULL)
    {
        return;
    }

    for (index = 0u; (index < UI_STATUS_LCD_COLUMNS) && (source[index] != '\0'); ++index)
    {
        destination[index] = source[index];
    }
}

static const char *ui_status_mode_name(app_mode_t mode)
{
    switch (mode)
    {
        case APP_MODE_WORK:
            return "WORK";

        case APP_MODE_ERROR:
            return "ERROR";

        case APP_MODE_IDLE:
        default:
            return "IDLE";
    }
}

static void ui_status_build_line_1(char *line_buffer)
{
    const char *label = g_profile_name;

    if (line_buffer == NULL)
    {
        return;
    }

    if (label[0] == '\0')
    {
        label = (g_mode == APP_MODE_WORK) ? "Manual control" : "No profile";
    }

    ui_status_copy_padded(line_buffer, label);
}

static void ui_status_build_line_2(char *line_buffer)
{
    char status_text[UI_STATUS_LCD_COLUMNS + 1u];

    if (line_buffer == NULL)
    {
        return;
    }

    if (g_error_flags == 0u)
    {
        (void)snprintf(status_text, sizeof(status_text), "%s OK", ui_status_mode_name(g_mode));
    }
    else
    {
        (void)snprintf(status_text, sizeof(status_text), "%s ERR %02X", ui_status_mode_name(g_mode), g_error_flags);
    }

    ui_status_copy_padded(line_buffer, status_text);
}

static void ui_status_refresh_display(void)
{
    char line_1[UI_STATUS_LCD_COLUMNS + 1u];
    char line_2[UI_STATUS_LCD_COLUMNS + 1u];

    if (g_initialised == 0u)
    {
        return;
    }

    ui_status_build_line_1(line_1);
    ui_status_build_line_2(line_2);
    lcd1602_display_set_lines(line_1, line_2);
    g_display_dirty = 0u;
}