// config_updater.c - Configuration file updater implementation
#define _POSIX_C_SOURCE 200809L
#include "config_updater.h"
#include "config_parser.h"
#include "secure_channel.h"
#include "debug_config.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>

#define PRIV_HEXKEY_LEN 65    // 32 bytes * 2 hex chars + null
#define PUB_HEXKEY_LEN 129    // 64 bytes * 2 hex chars + null
#define HEXNODEID_LEN 17      // 8 bytes * 2 hex chars + null
#define MAX_LINE_LEN 1024

void bytes_to_hex(const uint8_t *bytes, size_t len, char *hex_str, size_t hex_len) {
    if (!bytes || !hex_str || hex_len < len * 2 + 1) {
        if (hex_str && hex_len > 0) hex_str[0] = '\0';
        return;
    }
    for (size_t i = 0; i < len; i++) {
        snprintf(hex_str + i * 2, hex_len - i * 2, "%02x", bytes[i]);

    }
    hex_str[len * 2] = '\0';
}


static int is_valid_priv_key(const char *key) {
    if (!key || strlen(key) != 64) return 0;
    for (int i = 0; i < 64; i++) {
        if (!isxdigit((unsigned char)key[i])) return 0;
    }
    return 1;
}

static int is_valid_pub_key(const char *key) {
    if (!key || strlen(key) != 128) return 0;
    for (int i = 0; i < 128; i++) {
        if (!isxdigit((unsigned char)key[i])) return 0;
    }
    return 1;
}

static int is_valid_node_id(uint64_t node_id) {
    return node_id != 0;
}

static int read_file_to_mem(const char *filename, char **buffer, size_t *size) {
    FILE *fp = fopen(filename, "r");

    if (!fp) return -1;
    
    fseek(fp, 0, SEEK_END);

    long file_size = ftell(fp);

    if (file_size < 0) {
        fclose(fp);

        return -1;
    }
    fseek(fp, 0, SEEK_SET);

    
    *buffer = malloc(file_size + 1);

    if (!*buffer) {
        fclose(fp);

        return -1;
    }
    
    size_t read_size = fread(*buffer, 1, file_size, fp);

    if (read_size != (size_t)file_size) {
        free(*buffer);

        fclose(fp);

        return -1;
    }
    
    (*buffer)[file_size] = '\0';
    *size = file_size;
    fclose(fp);

    return 0;
}

static int write_mem_to_file(const char *filename, const char *buffer, size_t size) {
    FILE *fp = fopen(filename, "w");

    if (!fp) return -1;
    
    size_t written = fwrite(buffer, 1, size, fp);

    if (written != size) {
        fclose(fp);

        return -1;
    }
    
    fclose(fp);

    return 0;
}

static char* find_section_global(char *buf, size_t buf_len) {
    char *p = buf;
    while (p < buf + buf_len) {
        if (p[0] == '[' && strncmp(p + 1, "global", 6) == 0) {
            char *end = strchr(p, ']');

            if (end) return end + 1;
        }
        p = strchr(p, '\n');

        if (!p) break;
        p++;  // skip '\n'
    }
    return NULL;
}

static char* find_option(char *buf, size_t buf_len, const char *option) {
    char *p = buf;
    while (p < buf + buf_len) {
        if (strncmp(p, option, strlen(option)) == 0) {
            char *after_key = p + strlen(option);

            if (after_key[0] == '=') return p;
        }
        p = strchr(p, '\n');

        if (!p) break;
        p++;
    }
    return NULL;
}

static int insert_or_replace_option(char **buf, size_t *buf_len, size_t *buf_capacity, const char *option, const char *value) {
    if (!buf || !*buf || !buf_len || !buf_capacity || !option || !value) return -1;
    
    // Check if option already exists
    char *opt_pos = find_option(*buf, *buf_len, option);

    if (opt_pos) {
        // Find option line end
        char *line_end = strchr(opt_pos, '\n');

        if (!line_end) line_end = *buf + *buf_len;
        
        // Prepare new line
        char new_line[MAX_LINE_LEN];
        int new_len = snprintf(new_line, sizeof(new_line), "%s=%s\n", option, value);

        if (new_len <= 0 || new_len >= (int)sizeof(new_line)) return -1;
        
        // Calculate length difference
        size_t old_line_len = line_end - opt_pos + 1;
        long len_diff = new_len - old_line_len;
        
        // Ensure buffer capacity
        if (*buf_len + len_diff + 1 > *buf_capacity) {
            *buf_capacity = *buf_len + len_diff + 1024;
            char *new_buf = realloc(*buf, *buf_capacity);

            if (!new_buf) return -1;
            *buf = new_buf;
            // Recalculate positions after realloc
            opt_pos = find_option(*buf, *buf_len, option);

            if (!opt_pos) return -1;
            line_end = strchr(opt_pos, '\n');

            if (!line_end) line_end = *buf + *buf_len;
        }
        
        // Move content and insert new line
        memmove(opt_pos + new_len, line_end, *buf_len - (line_end - *buf) + 1);

        memcpy(opt_pos, new_line, new_len);

        *buf_len += len_diff;
        
    } else {
        // Insert after [global] section
        char *section_end = find_section_global(*buf, *buf_len);

        if (!section_end) return -1;
        
        // Find end of global section (next [ or end of buffer)
        char *insert_pos = strchr(section_end, '[');

        if (!insert_pos) insert_pos = *buf + *buf_len;
        else {
            // Move to beginning of next line
            char *prev_nl = insert_pos;
            while (prev_nl > *buf && *prev_nl != '\n') prev_nl--;
            if (*prev_nl == '\n') insert_pos = prev_nl + 1;
        }
        
        // Prepare new line
        char new_line[MAX_LINE_LEN];
        int new_len = snprintf(new_line, sizeof(new_line), "%s=%s\n", option, value);

        if (new_len <= 0 || new_len >= (int)sizeof(new_line)) return -1;
        
        // Ensure buffer capacity
        if (*buf_len + new_len + 1 > *buf_capacity) {
            *buf_capacity = *buf_len + new_len + 1024;
            char *new_buf = realloc(*buf, *buf_capacity);

            if (!new_buf) return -1;
            *buf = new_buf;
            // Recalculate insert position after realloc
            section_end = find_section_global(*buf, *buf_len);

            if (!section_end) return -1;
            insert_pos = strchr(section_end, '[');

            if (!insert_pos) insert_pos = *buf + *buf_len;
            else {
                char *prev_nl = insert_pos;
                while (prev_nl > *buf && *prev_nl != '\n') prev_nl--;
                if (*prev_nl == '\n') insert_pos = prev_nl + 1;
            }
        }
        
        // Move content and insert new line
        memmove(insert_pos + new_len, insert_pos, *buf_len - (insert_pos - *buf) + 1);

        memcpy(insert_pos, new_line, new_len);

        *buf_len += new_len;
    }
    
    return 0;
}

int config_ensure_keys_and_node_id(const char *filename) {
    struct utun_config *config = parse_config(filename);

    if (!config) {
        printf("[CONFIG ERROR] Failed to parse config: %s\n", filename);

        return -1;
    }
    
    struct global_config *global = &config->global;
    
    // Debug: print what we found
    printf("[CONFIG DEBUG] Checking config - priv_key='%s' (len=%zu), pub_key='%s' (len=%zu), node_id=%llu\n",
           global->my_private_key_hex ? global->my_private_key_hex : "NULL",
           global->my_private_key_hex ? strlen(global->my_private_key_hex) : 0,
           global->my_public_key_hex ? global->my_public_key_hex : "NULL", 
           global->my_public_key_hex ? strlen(global->my_public_key_hex) : 0,
           (unsigned long long)global->my_node_id);

    
    // Check if we need to generate anything
    int need_priv_key = !is_valid_priv_key(global->my_private_key_hex);

    int need_pub_key = !is_valid_pub_key(global->my_public_key_hex);

    int need_node_id = !is_valid_node_id(global->my_node_id);

    
    printf("[CONFIG DEBUG] Validation results - need_priv_key=%d, need_pub_key=%d, need_node_id=%d\n",
           need_priv_key, need_pub_key, need_node_id);

    
    if (!need_priv_key && !need_pub_key && !need_node_id) {
        free_config(config);

        return 0;
    }
    
    // Generate keys if needed
    char new_priv_key[PRIV_HEXKEY_LEN] = {0};
    char new_pub_key[PUB_HEXKEY_LEN] = {0};
    uint64_t new_node_id = 0;
    
    if (need_priv_key) {
        // Generate new keypair if private key is invalid
        struct SC_MYKEYS mykeys;
        if (sc_generate_keypair(&mykeys) != SC_OK) {
            printf( "Failed to generate keypair");

            free_config(config);

            return -1;
        }
        bytes_to_hex(mykeys.private_key, SC_PRIVKEY_SIZE, new_priv_key, sizeof(new_priv_key));

        bytes_to_hex(mykeys.public_key, SC_PUBKEY_SIZE, new_pub_key, sizeof(new_pub_key));

    } else if (need_pub_key) {
        // Compute public key from existing private key
        uint8_t priv_bin[SC_PRIVKEY_SIZE];
        uint8_t pub_bin[SC_PUBKEY_SIZE];
        
        // Convert private key from hex to binary
        for (int i = 0; i < SC_PRIVKEY_SIZE; i++) {
            unsigned int byte;
            if (sscanf(global->my_private_key_hex + i * 2, "%2x", &byte) != 1) {
                printf( "Invalid private key hex format");

                free_config(config);

                return -1;
            }
            priv_bin[i] = (uint8_t)byte;
        }
        
        // Compute public key
        if (sc_compute_public_key_from_private(priv_bin, pub_bin) != SC_OK) {
            printf( "Failed to compute public key from private key");

            free_config(config);

            return -1;
        }
        
        // Convert to hex
        bytes_to_hex(priv_bin, SC_PRIVKEY_SIZE, new_priv_key, sizeof(new_priv_key));

        bytes_to_hex(pub_bin, SC_PUBKEY_SIZE, new_pub_key, sizeof(new_pub_key));

    }
    
    if (need_node_id) {
        int fd = open("/dev/urandom", O_RDONLY);

        if (fd < 0) {
            printf( "Failed to open /dev/urandom");

            free_config(config);

            return -1;
        }
        if (read(fd, &new_node_id, sizeof(new_node_id)) != sizeof(new_node_id)) {
            close(fd);

            printf( "Failed to read random bytes for node_id");

            free_config(config);

            return -1;
        }
        close(fd);

        new_node_id &= 0x7FFFFFFFFFFFFFFF;
    }
    
    free_config(config);

    
    // Read entire config file to memory
    char *file_buf = NULL;
    size_t file_size = 0;
    if (read_file_to_mem(filename, &file_buf, &file_size) < 0) {
        printf( "Failed to read config file: %s", filename);

        return -1;
    }
    
    // Update config file
    size_t buf_capacity = file_size + 1024;
    char *work_buf = malloc(buf_capacity);

    if (!work_buf) {
        free(file_buf);

        return -1;
    }
    memcpy(work_buf, file_buf, file_size);

    size_t work_len = file_size;
    
    int ret = 0;
    
    if (need_node_id) {
        char node_id_hex[HEXNODEID_LEN + 1];
        snprintf(node_id_hex, sizeof(node_id_hex), "%llx", (unsigned long long)new_node_id);

        if (insert_or_replace_option(&work_buf, &work_len, &buf_capacity, "my_node_id", node_id_hex) < 0) {
            ret = -1;
        }
    }
    
    if (need_priv_key && ret == 0) {
        if (insert_or_replace_option(&work_buf, &work_len, &buf_capacity, "my_private_key", new_priv_key) < 0) {
            ret = -1;
        }
    }
    
    if (need_pub_key && ret == 0) {
        if (insert_or_replace_option(&work_buf, &work_len, &buf_capacity, "my_public_key", new_pub_key) < 0) {
            ret = -1;
        }
    }
    
    if (ret == 0) {
        printf("[CONFIG DEBUG] Writing updated config file, work_len=%zu\n", work_len);

        if (write_mem_to_file(filename, work_buf, work_len) < 0) {
            printf( "Failed to write updated config file: %s", filename);

            ret = -1;
        } else {
            printf("[CONFIG DEBUG] Successfully updated config file: %s\n", filename);

        }
    }
    
    free(file_buf);

    free(work_buf);

    
    return ret;
}