/**
 * @file gpio_linux.c
 * @brief GPIO implementation for Linux using libgpiod and KED callback injection.
 */

#include "../../ked/peripherals/gpio/gpio.h"
#include <gpiod.h>
#include <stdlib.h>
#include <stdio.h>

/**
 * @brief Internal Linux GPIO context.
 *
 * Holds pointers to the open GPIO chip and the requested line.
 */
typedef struct {
    struct gpiod_chip* chip; /**< File descriptor to the opened GPIO chip */
    struct gpiod_line* line; /**< Reference to the requested GPIO line */
} gpio_linux_ctx_t;

static gpio_linux_ctx_t gpio_ctx;

/**
 * @brief Set the output level of the GPIO line.
 *
 * @param value Logic level to set (true for HIGH, false for LOW).
 */
static void gpio_linux_set(bool value) {
    gpiod_line_set_value(gpio_ctx.line, value);
}

/**
 * @brief Read the current logic level of the GPIO line.
 *
 * @return Logic level (true for HIGH, false for LOW).
 */
static bool gpio_linux_read(void) {
    return gpiod_line_get_value(gpio_ctx.line);
}

/**
 * @brief Toggle the current state of the GPIO output.
 */
static void gpio_linux_toggle(void) {
    int current = gpiod_line_get_value(gpio_ctx.line);
    gpiod_line_set_value(gpio_ctx.line, !current);
}

/**
 * @brief Release the GPIO line and chip.
 *
 * Called during deinitialization to free resources.
 */
static void gpio_linux_deinit(void) {
    if (gpio_ctx.line) {
        gpiod_line_release(gpio_ctx.line);
        gpio_ctx.line = NULL;
    }
    if (gpio_ctx.chip) {
        gpiod_chip_close(gpio_ctx.chip);
        gpio_ctx.chip = NULL;
    }
}

/**
 * @brief Default error handling function.
 *
 * @param err The GPIO error code to report.
 */
static void gpio_linux_handle_error(gpio_error_t err) {
    fprintf(stderr, "[GPIO ERROR] Code: %d\n", err);
}

/**
 * @brief Initialize a GPIO using a Linux-specific gpio_config.
 *
 * Sets the direction and bias of the line according to the config.
 *
 * @param gpio Pointer to a gpio_t handle to be configured.
 * @param config Pointer to a Linux-specific gpio_config structure.
 * @return GPIO_OK on success or an appropriate gpio_error_t on failure.
 */
gpio_error_t ked_gpio_init(gpio_t* gpio, const gpio_config* config) {
    gpio_ctx.chip = gpiod_chip_open(config->chipname);
    if (!gpio_ctx.chip) {
        gpio->on_error(GPIO_ERR_NOT_AVAILABLE);
        return GPIO_ERR_NOT_AVAILABLE;
    }

    gpio_ctx.line = gpiod_chip_get_line(gpio_ctx.chip, config->line_offset);
    if (!gpio_ctx.line) {
        gpiod_chip_close(gpio_ctx.chip);
        gpio->on_error(GPIO_ERR_NOT_AVAILABLE);
        return GPIO_ERR_NOT_AVAILABLE;
    }

    struct gpiod_line_request_config req_cfg = {
        .consumer = "ked",
        .request_type = (config->direction == GPIO_DIRECTION_OUTPUT)
            ? GPIOD_LINE_REQUEST_DIRECTION_OUTPUT
            : GPIOD_LINE_REQUEST_DIRECTION_INPUT,
        .flags = 0
    };

    if (config->bias == GPIO_BIAS_PULL_UP) {
        req_cfg.flags |= GPIOD_LINE_REQUEST_FLAG_BIAS_PULL_UP;
    } else if (config->bias == GPIO_BIAS_PULL_DOWN) {
        req_cfg.flags |= GPIOD_LINE_REQUEST_FLAG_BIAS_PULL_DOWN;
    } else if (config->bias == GPIO_BIAS_DISABLE) {
        req_cfg.flags |= GPIOD_LINE_REQUEST_FLAG_BIAS_DISABLE;
    } else if (config->bias == GPIO_BIAS_NONE) {
        req_cfg.request_type = GPIOD_LINE_REQUEST_DIRECTION_AS_IS;
    }

    if (gpiod_line_request(gpio_ctx.line, &req_cfg, 0) < 0) {
        gpiod_chip_close(gpio_ctx.chip);
        gpio->on_error(GPIO_ERR_LINE_BUSY);
        return GPIO_ERR_LINE_BUSY;
    }

    gpio->set = gpio_linux_set;
    gpio->read = gpio_linux_read;
    gpio->toggle = gpio_linux_toggle;
    gpio->deinit = gpio_linux_deinit;
    gpio->on_error = gpio_linux_handle_error;

    return GPIO_OK;
}

/**
 * @brief Generic GPIO deinitialization entry point.
 *
 * @param gpio Pointer to the gpio_t structure with deinit function populated.
 */
void ked_gpio_deinit(gpio_t* gpio) {
    if (gpio && gpio->deinit) {
        gpio->deinit();
    }
}