/**
 * @file chunk_client.c
 * @brief Chunk Transfer Client Implementation
 * 
 * Note: This implementation requires an HTTP client library.
 * For ESP32, use ESP-IDF's HTTP Client or Arduino's HTTPClient.
 * For POSIX systems, use libcurl.
 */

#include "protocol.h"
#include <string.h>
#include <stdio.h>

/* HTTP client interface (to be implemented per platform) */
typedef struct {
    /**
     * Send HTTP GET request
     * @param url Full URL
     * @param response Buffer for response data
     * @param response_len Buffer size
     * @param actual_len Actual response length (output)
     * @param status_code HTTP status code (output)
     * @return 0 on success, error code otherwise
     */
    int (*http_get)(const char *url, uint8_t *response, size_t response_len,
                    size_t *actual_len, int *status_code);
    
    /**
     * Get header value from last response
     * @param name Header name
     * @return Header value or NULL
     */
    const char *(*http_get_header)(const char *name);
    
    void *ctx;  /* Platform-specific context */
} http_client_t;

/* Client state */
typedef struct {
    chunk_client_config_t config;
    http_client_t http;
    
    char current_file[256];
    uint32_t file_size;
    uint16_t total_chunks;
    uint16_t current_chunk;
    chunk_state_t state;
    chunk_err_t error_code;
    bool cancel_requested;
} chunk_client_state_t;

static chunk_client_state_t client_state;

/**
 * Initialize chunk client
 */
chunk_err_t chunk_client_init(const chunk_client_config_t *config) {
    if (!config || !config->server_url) {
        return CHUNK_ERR_INVALID_PARAM;
    }
    
    memset(&client_state, 0, sizeof(client_state));
    memcpy(&client_state.config, config, sizeof(chunk_client_config_t));
    
    /* Set default chunk size if not specified */
    if (client_state.config.chunk_size == 0) {
        client_state.config.chunk_size = CHUNK_DEFAULT_SIZE;
    }
    
    client_state.state = CHUNK_STATE_IDLE;
    client_state.error_code = CHUNK_ERR_OK;
    
    return CHUNK_ERR_OK;
}

/**
 * Get file size from server
 */
static chunk_err_t get_file_size(const char *filename, uint32_t *size) {
    char url[512];
    snprintf(url, sizeof(url), "%s/ota?file=%s", 
             client_state.config.server_url, filename);
    
    /* Send HEAD or GET request to get Content-Length */
    uint8_t dummy[1];
    size_t actual_len;
    int status_code;
    
    int ret = client_state.http.http_get(url, dummy, sizeof(dummy), 
                                         &actual_len, &status_code);
    if (ret != 0) {
        return CHUNK_ERR_NETWORK;
    }
    
    if (status_code != 200) {
        return (status_code == 404) ? CHUNK_ERR_FILE_NOT_FOUND : CHUNK_ERR_SERVER_ERROR;
    }
    
    /* Parse Content-Length from headers */
    const char *cl = client_state.http.http_get_header("X-File-Size");
    if (!cl) {
        cl = client_state.http.http_get_header("Content-Length");
    }
    
    if (cl) {
        *size = (uint32_t)atoi(cl);
    } else {
        /* Fallback: estimate from first chunk */
        *size = client_state.config.chunk_size;
    }
    
    return CHUNK_ERR_OK;
}

/**
 * Download a single chunk
 */
static chunk_err_t download_chunk(uint16_t chunk_idx, uint8_t *buffer, 
                                   uint16_t *payload_len, uint32_t *crc32) {
    char url[512];
    snprintf(url, sizeof(url), "%s/ota?file=%s&chunk=%u",
             client_state.config.server_url, 
             client_state.current_file, chunk_idx);
    
    /* Allocate buffer for chunk response */
    size_t response_size = 2 + client_state.config.chunk_size + 4;
    uint8_t *response = (uint8_t *)malloc(response_size);
    if (!response) {
        return CHUNK_ERR_MEMORY;
    }
    
    size_t actual_len;
    int status_code;
    
    int ret = client_state.http.http_get(url, response, response_size,
                                         &actual_len, &status_code);
    
    if (ret != 0) {
        free(response);
        return CHUNK_ERR_NETWORK;
    }
    
    if (status_code == 416) {
        free(response);
        return CHUNK_ERR_RANGE_INVALID;
    }
    
    if (status_code != 200 && status_code != 206) {
        free(response);
        return CHUNK_ERR_SERVER_ERROR;
    }
    
    /* Parse chunk: [chunk_idx: 2B][payload: N B][crc32: 4B] */
    if (actual_len < 6) {  /* Minimum: 2 + 0 + 4 */
        free(response);
        return CHUNK_ERR_NETWORK;
    }
    
    uint16_t received_idx = (response[0] << 8) | response[1];
    if (received_idx != chunk_idx) {
        free(response);
        return CHUNK_ERR_NETWORK;  /* Chunk index mismatch */
    }
    
    /* Calculate payload length */
    uint16_t total_chunk_size = client_state.config.chunk_size;
    uint32_t remaining = client_state.file_size - (uint32_t)chunk_idx * total_chunk_size;
    uint16_t expected_payload = (uint16_t)(remaining < total_chunk_size ? remaining : total_chunk_size);
    
    if (actual_len != 2 + expected_payload + 4) {
        /* Last chunk might have different size */
        if (chunk_idx == client_state.total_chunks - 1) {
            *payload_len = (uint16_t)(actual_len - 6);
        } else {
            free(response);
            return CHUNK_ERR_NETWORK;
        }
    } else {
        *payload_len = expected_payload;
    }
    
    /* Copy payload */
    memcpy(buffer, response + 2, *payload_len);
    
    /* Extract CRC32 */
    *crc32 = (response[2 + *payload_len] << 24) |
             (response[3 + *payload_len] << 16) |
             (response[4 + *payload_len] << 8) |
             response[5 + *payload_len];
    
    free(response);
    return CHUNK_ERR_OK;
}

/**
 * Start file download
 */
chunk_err_t chunk_client_download(const char *filename) {
    if (!filename) {
        return CHUNK_ERR_INVALID_PARAM;
    }
    
    /* Store filename */
    strncpy(client_state.current_file, filename, sizeof(client_state.current_file) - 1);
    client_state.current_file[sizeof(client_state.current_file) - 1] = '\0';
    
    /* Get file size */
    chunk_err_t err = get_file_size(filename, &client_state.file_size);
    if (err != CHUNK_ERR_OK) {
        client_state.state = CHUNK_STATE_ERROR;
        client_state.error_code = err;
        if (client_state.config.on_error) {
            client_state.config.on_error(err, client_state.config.user_ctx);
        }
        return err;
    }
    
    /* Calculate total chunks */
    client_state.total_chunks = chunk_calc_total_chunks(
        client_state.file_size, client_state.config.chunk_size);
    
    client_state.current_chunk = 0;
    client_state.state = CHUNK_STATE_TRANSFERRING;
    client_state.cancel_requested = false;
    
    /* Buffer for chunk payload */
    uint8_t *payload = (uint8_t *)malloc(client_state.config.chunk_size);
    if (!payload) {
        client_state.state = CHUNK_STATE_ERROR;
        client_state.error_code = CHUNK_ERR_MEMORY;
        return CHUNK_ERR_MEMORY;
    }
    
    /* Download all chunks */
    for (uint16_t i = 0; i < client_state.total_chunks; i++) {
        if (client_state.cancel_requested) {
            free(payload);
            client_state.state = CHUNK_STATE_IDLE;
            return CHUNK_ERR_OK;  /* Cancel is not an error */
        }
        
        uint16_t payload_len;
        uint32_t crc32;
        
        err = download_chunk(i, payload, &payload_len, &crc32);
        if (err != CHUNK_ERR_OK) {
            free(payload);
            client_state.state = CHUNK_STATE_ERROR;
            client_state.error_code = err;
            if (client_state.config.on_error) {
                client_state.config.on_error(err, client_state.config.user_ctx);
            }
            return err;
        }
        
        /* Verify CRC32 */
        uint32_t calculated_crc = chunk_crc32(payload, payload_len);
        if (calculated_crc != crc32) {
            free(payload);
            client_state.state = CHUNK_STATE_ERROR;
            client_state.error_code = CHUNK_ERR_CRC;
            if (client_state.config.on_error) {
                client_state.config.on_error(CHUNK_ERR_CRC, client_state.config.user_ctx);
            }
            return CHUNK_ERR_CRC;
        }
        
        /* Call chunk received callback */
        if (client_state.config.on_chunk_received) {
            client_state.config.on_chunk_received(i, payload, payload_len, 
                                                   client_state.config.user_ctx);
        }
        
        /* Progress callback */
        if (client_state.config.on_progress) {
            client_state.config.on_progress(i + 1, client_state.total_chunks,
                                            client_state.config.user_ctx);
        }
        
        client_state.current_chunk = i + 1;
    }
    
    free(payload);
    
    /* Transfer complete */
    client_state.state = CHUNK_STATE_COMPLETE;
    if (client_state.config.on_complete) {
        client_state.config.on_complete(client_state.file_size, 
                                        client_state.config.user_ctx);
    }
    
    return CHUNK_ERR_OK;
}

/**
 * Resume download from specific chunk
 */
chunk_err_t chunk_client_resume(const char *filename, uint16_t start_chunk) {
    if (!filename) {
        return CHUNK_ERR_INVALID_PARAM;
    }
    
    /* Store filename */
    strncpy(client_state.current_file, filename, sizeof(client_state.current_file) - 1);
    client_state.current_file[sizeof(client_state.current_file) - 1] = '\0';
    
    /* Get file size */
    chunk_err_t err = get_file_size(filename, &client_state.file_size);
    if (err != CHUNK_ERR_OK) {
        client_state.state = CHUNK_STATE_ERROR;
        client_state.error_code = err;
        if (client_state.config.on_error) {
            client_state.config.on_error(err, client_state.config.user_ctx);
        }
        return err;
    }
    
    /* Calculate total chunks */
    client_state.total_chunks = chunk_calc_total_chunks(
        client_state.file_size, client_state.config.chunk_size);
    
    /* Validate start chunk */
    if (start_chunk >= client_state.total_chunks) {
        return CHUNK_ERR_RANGE_INVALID;
    }
    
    client_state.current_chunk = start_chunk;
    client_state.state = CHUNK_STATE_RESUMING;
    client_state.cancel_requested = false;
    
    /* Buffer for chunk payload */
    uint8_t *payload = (uint8_t *)malloc(client_state.config.chunk_size);
    if (!payload) {
        client_state.state = CHUNK_STATE_ERROR;
        client_state.error_code = CHUNK_ERR_MEMORY;
        return CHUNK_ERR_MEMORY;
    }
    
    /* Download remaining chunks */
    for (uint16_t i = start_chunk; i < client_state.total_chunks; i++) {
        if (client_state.cancel_requested) {
            free(payload);
            client_state.state = CHUNK_STATE_IDLE;
            return CHUNK_ERR_OK;
        }
        
        uint16_t payload_len;
        uint32_t crc32;
        
        err = download_chunk(i, payload, &payload_len, &crc32);
        if (err != CHUNK_ERR_OK) {
            free(payload);
            client_state.state = CHUNK_STATE_ERROR;
            client_state.error_code = err;
            if (client_state.config.on_error) {
                client_state.config.on_error(err, client_state.config.user_ctx);
            }
            return err;
        }
        
        /* Verify CRC32 */
        uint32_t calculated_crc = chunk_crc32(payload, payload_len);
        if (calculated_crc != crc32) {
            free(payload);
            client_state.state = CHUNK_STATE_ERROR;
            client_state.error_code = CHUNK_ERR_CRC;
            if (client_state.config.on_error) {
                client_state.config.on_error(CHUNK_ERR_CRC, client_state.config.user_ctx);
            }
            return CHUNK_ERR_CRC;
        }
        
        /* Call chunk received callback */
        if (client_state.config.on_chunk_received) {
            client_state.config.on_chunk_received(i, payload, payload_len,
                                                   client_state.config.user_ctx);
        }
        
        /* Progress callback */
        if (client_state.config.on_progress) {
            client_state.config.on_progress(i + 1, client_state.total_chunks,
                                            client_state.config.user_ctx);
        }
        
        client_state.current_chunk = i + 1;
    }
    
    free(payload);
    
    /* Transfer complete */
    client_state.state = CHUNK_STATE_COMPLETE;
    if (client_state.config.on_complete) {
        client_state.config.on_complete(client_state.file_size,
                                        client_state.config.user_ctx);
    }
    
    return CHUNK_ERR_OK;
}

/**
 * Cancel current transfer
 */
void chunk_client_cancel(void) {
    client_state.cancel_requested = true;
}

/**
 * Get current transfer state
 */
chunk_state_t chunk_client_get_state(void) {
    return client_state.state;
}

/**
 * Get current progress
 */
chunk_err_t chunk_client_get_progress(uint16_t *current_chunk, uint16_t *total_chunks) {
    if (!current_chunk || !total_chunks) {
        return CHUNK_ERR_INVALID_PARAM;
    }
    
    *current_chunk = client_state.current_chunk;
    *total_chunks = client_state.total_chunks;
    
    return CHUNK_ERR_OK;
}

/**
 * Cleanup client resources
 */
void chunk_client_cleanup(void) {
    memset(&client_state, 0, sizeof(client_state));
}