// config_parser.c - Configuration parser for utun application
#define _POSIX_C_SOURCE 200809L
#include "config_parser.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <ctype.h>
#include <errno.h>

#define MAX_LINE_LEN 1024
#define INITIAL_CONNECTION_CAPACITY 4

// Helper function to trim whitespace
static char* trim(char *str) {
    if (!str) return NULL;
    
    // Trim leading spaces
    while (isspace((unsigned char)*str)) str++;
    
    // Trim trailing spaces
    char *end = str + strlen(str) - 1;
    while (end > str && isspace((unsigned char)*end)) end--;
    *(end + 1) = '\0';
    
    return str;
}

// Parse a key-value pair
static int parse_key_value(const char *line, char *key, size_t key_len, 
                           char *value, size_t value_len) {
    char *equal = strchr(line, '=');
    if (!equal) return -1;
    
    // Extract key
    size_t key_size = equal - line;
    if (key_size >= key_len) return -1;
    strncpy(key, line, key_size);
    key[key_size] = '\0';
    trim(key);
    
    // Extract value
    const char *val_start = equal + 1;
    size_t val_len = strlen(val_start);
    if (val_len >= value_len) return -1;
    strcpy(value, val_start);
    trim(value);
    
    return 0;
}

// Parse connection mode string
static config_conn_mode_t parse_mode(const char *mode_str) {
    if (!mode_str) return CONFIG_MODE_UNKNOWN;
    
    if (strcasecmp(mode_str, "client") == 0) {
        return CONFIG_MODE_CLIENT;
    } else if (strcasecmp(mode_str, "server") == 0) {
        return CONFIG_MODE_SERVER;
    }
    
    return CONFIG_MODE_UNKNOWN;
}

// Add a connection to the config
static int add_connection(utun_config_t *config, const connection_config_t *conn) {
    if (config->connection_count >= config->connection_capacity) {
        // Resize array
        int new_capacity = config->connection_capacity * 2;
        connection_config_t *new_connections = realloc(config->connections, 
                                                      new_capacity * sizeof(connection_config_t));
        if (!new_connections) return -1;
        
        config->connections = new_connections;
        config->connection_capacity = new_capacity;
    }
    
    // Copy connection data
    memcpy(&config->connections[config->connection_count], conn, sizeof(connection_config_t));
    config->connection_count++;
    
    return 0;
}

// Parse configuration file
utun_config_t* parse_config(const char *filename) {
    FILE *fp = fopen(filename, "r");
    if (!fp) {
        fprintf(stderr, "Failed to open config file: %s\n", filename);
        return NULL;
    }
    
    // Allocate config structure
    utun_config_t *config = calloc(1, sizeof(utun_config_t));
    if (!config) {
        fclose(fp);
        return NULL;
    }
    
    // Initialize connection array
    config->connection_capacity = INITIAL_CONNECTION_CAPACITY;
    config->connections = malloc(config->connection_capacity * sizeof(connection_config_t));
    if (!config->connections) {
        free(config);
        fclose(fp);
        return NULL;
    }
    
    char line[MAX_LINE_LEN];
    char current_section[128] = "";
    connection_config_t current_conn = {0};
    int in_connection_section = 0;
    
    while (fgets(line, sizeof(line), fp)) {
        // Remove newline
        line[strcspn(line, "\n")] = '\0';
        
        char *trimmed = trim(line);
        
        // Skip empty lines and comments
        if (strlen(trimmed) == 0 || trimmed[0] == ';' || trimmed[0] == '#') {
            continue;
        }
        
        // Check for section header
        if (trimmed[0] == '[' && trimmed[strlen(trimmed) - 1] == ']') {
            // End previous connection section if any
            if (in_connection_section) {
                if (strlen(current_conn.name) > 0) {
                    if (add_connection(config, &current_conn) != 0) {
                        fprintf(stderr, "Failed to add connection: %s\n", current_conn.name);
                    }
                }
                memset(&current_conn, 0, sizeof(current_conn));
                in_connection_section = 0;
            }
            
            // Extract section name
            strncpy(current_section, trimmed + 1, sizeof(current_section) - 1);
            current_section[sizeof(current_section) - 1] = '\0';
            current_section[strcspn(current_section, "]")] = '\0';
            trim(current_section);
            
            // Check if it's a connection section
            if (strncmp(current_section, "connection:", 11) == 0) {
                in_connection_section = 1;
                // Extract connection name
                char *name = trim(current_section + 11);
                if (strlen(name) > 0) {
                    strncpy(current_conn.name, name, sizeof(current_conn.name) - 1);
                }
            }
            
            continue;
        }
        
        // Parse key-value pair
        char key[256], value[256];
        if (parse_key_value(trimmed, key, sizeof(key), value, sizeof(value)) != 0) {
            fprintf(stderr, "Invalid key-value line: %s\n", trimmed);
            continue;
        }
        
        // Process based on current section
        if (strcasecmp(current_section, "global") == 0) {
            if (strcasecmp(key, "my_private_key") == 0) {
                strncpy(config->global.my_private_key_hex, value, sizeof(config->global.my_private_key_hex) - 1);
            } else if (strcasecmp(key, "my_public_key") == 0) {
                strncpy(config->global.my_public_key_hex, value, sizeof(config->global.my_public_key_hex) - 1);
            } else if (strcasecmp(key, "option") == 0) {
                strncpy(config->global.option_value, value, sizeof(config->global.option_value) - 1);
            } else if (strcasecmp(key, "control_ip") == 0) {
                strncpy(config->global.control_ip, value, sizeof(config->global.control_ip) - 1);
            } else if (strcasecmp(key, "control_port") == 0) {
                config->global.control_port = atoi(value);
            } else if (strcasecmp(key, "net_debug") == 0) {
                config->global.net_debug = atoi(value);
            }
        } else if (strcasecmp(current_section, "routing") == 0) {
            if (strcasecmp(key, "allowed_subnet") == 0) {
                if (config->allowed_subnet_count < MAX_ALLOWED_SUBNETS) {
                    strncpy(config->allowed_subnets[config->allowed_subnet_count].subnet, value, sizeof(config->allowed_subnets[0].subnet) - 1);
                    config->allowed_subnet_count++;
                } else {
                    fprintf(stderr, "Too many allowed subnets, maximum is %d\n", MAX_ALLOWED_SUBNETS);
                }
            }
        } else if (in_connection_section) {
            if (strcasecmp(key, "mode") == 0) {
                current_conn.mode = parse_mode(value);
            } else if (strcasecmp(key, "addr") == 0) {
                // For server mode
                if (current_conn.mode == CONFIG_MODE_SERVER) {
                    strncpy(current_conn.local_addr, value, sizeof(current_conn.local_addr) - 1);
                }
            } else if (strcasecmp(key, "from_addr") == 0) {
                // For client mode
                if (current_conn.mode == CONFIG_MODE_CLIENT) {
                    strncpy(current_conn.local_addr, value, sizeof(current_conn.local_addr) - 1);
                }
            } else if (strcasecmp(key, "to_addr") == 0) {
                // For client mode
                if (current_conn.mode == CONFIG_MODE_CLIENT) {
                    strncpy(current_conn.remote_addr, value, sizeof(current_conn.remote_addr) - 1);
                }
            } else if (strcasecmp(key, "peer_public_key") == 0) {
                strncpy(current_conn.peer_public_key_hex, value, sizeof(current_conn.peer_public_key_hex) - 1);
            } else if (strcasecmp(key, "so_mark") == 0) {
                current_conn.so_mark = atoi(value);
            } else if (strcasecmp(key, "netif") == 0) {
                strncpy(current_conn.netif, value, sizeof(current_conn.netif) - 1);
            } else if (strcasecmp(key, "tun") == 0) {
                strncpy(current_conn.tun_ifname, value, sizeof(current_conn.tun_ifname) - 1);
            } else if (strcasecmp(key, "tun_ip") == 0) {
                strncpy(current_conn.tun_ip, value, sizeof(current_conn.tun_ip) - 1);
            }
        }
    }
    
    // Add last connection if any
    if (in_connection_section && strlen(current_conn.name) > 0) {
        if (add_connection(config, &current_conn) != 0) {
            fprintf(stderr, "Failed to add connection: %s\n", current_conn.name);
        }
    }
    
    fclose(fp);
    return config;
}

// Free configuration structure
void free_config(utun_config_t *config) {
    if (!config) return;
    
    if (config->connections) {
        free(config->connections);
    }
    free(config);
}

// Print configuration for debugging
void print_config(const utun_config_t *config) {
    if (!config) {
        printf("Configuration is NULL\n");
        return;
    }
    
    printf("Global configuration:\n");
    printf("  my_private_key: %s\n", config->global.my_private_key_hex);
    printf("  my_public_key: %s\n", config->global.my_public_key_hex);
    printf("  option: %s\n", config->global.option_value);
    printf("  control_ip: %s\n", config->global.control_ip);
    printf("  control_port: %u\n", config->global.control_port);
    printf("  net_debug: %d\n", config->global.net_debug);
    printf("\n");
    printf("Allowed subnets (%d):\n", config->allowed_subnet_count);
    for (int i = 0; i < config->allowed_subnet_count; i++) {
        printf("  %s\n", config->allowed_subnets[i].subnet);
    }
    printf("\n");
    
    printf("Connections (%d):\n", config->connection_count);
    for (int i = 0; i < config->connection_count; i++) {
        const connection_config_t *conn = &config->connections[i];
        printf("  [%d] %s:\n", i, conn->name);
        printf("    mode: %s\n", 
               conn->mode == CONFIG_MODE_CLIENT ? "client" : 
               conn->mode == CONFIG_MODE_SERVER ? "server" : "unknown");
        printf("    local_addr: %s\n", conn->local_addr);
        printf("    remote_addr: %s\n", conn->remote_addr);
        printf("    peer_public_key: %s\n", conn->peer_public_key_hex);
        printf("    so_mark: %d\n", conn->so_mark);
        printf("    netif: %s\n", conn->netif);
        printf("    tun: %s\n", conn->tun_ifname);
        printf("    tun_ip: %s\n", conn->tun_ip);
    }
}

// Update keys in configuration file
int update_config_keys(const char *filename, 
                       const char *private_key_hex, 
                       const char *public_key_hex) {
    if (!filename || !private_key_hex || !public_key_hex) {
        errno = EINVAL;
        return -1;
    }
    
    // Read entire file
    FILE *fp = fopen(filename, "r");
    if (!fp) {
        // Try to create new file
        fp = fopen(filename, "w");
        if (!fp) return -1;
        
        fprintf(fp, "[global]\n");
        fprintf(fp, "my_private_key=%s\n", private_key_hex);
        fprintf(fp, "my_public_key=%s\n", public_key_hex);
        fclose(fp);
        return 0;
    }
    
    // Read all lines
    char **lines = NULL;
    size_t line_count = 0;
    size_t capacity = 0;
    char line[MAX_LINE_LEN];
    int in_global_section = 0;
    int private_key_found = 0;
    int public_key_found = 0;
    size_t private_key_line = 0;
    size_t public_key_line = 0;
    
    while (fgets(line, sizeof(line), fp)) {
        // Add line to array
        if (line_count >= capacity) {
            size_t new_capacity = capacity ? capacity * 2 : 16;
            char **new_lines = realloc(lines, new_capacity * sizeof(char *));
            if (!new_lines) {
                // Cleanup
                for (size_t i = 0; i < line_count; i++) free(lines[i]);
                free(lines);
                fclose(fp);
                return -1;
            }
            lines = new_lines;
            capacity = new_capacity;
        }
        
        lines[line_count] = strdup(line);
        if (!lines[line_count]) {
            // Cleanup
            for (size_t i = 0; i < line_count; i++) free(lines[i]);
            free(lines);
            fclose(fp);
            return -1;
        }
        
        char *trimmed = trim(line);
        
        // Track global section
        if (trimmed[0] == '[' && trimmed[strlen(trimmed) - 1] == ']') {
            char section[128];
            strncpy(section, trimmed + 1, sizeof(section) - 1);
            section[sizeof(section) - 1] = '\0';
            section[strcspn(section, "]")] = '\0';
            trim(section);
            
            in_global_section = (strcasecmp(section, "global") == 0);
        }
        
        // Check for keys in global section
        if (in_global_section) {
            char key[256], value[256];
            if (parse_key_value(trimmed, key, sizeof(key), value, sizeof(value)) == 0) {
                if (strcasecmp(key, "my_private_key") == 0) {
                    private_key_found = 1;
                    private_key_line = line_count;
                } else if (strcasecmp(key, "my_public_key") == 0) {
                    public_key_found = 1;
                    public_key_line = line_count;
                }
            }
        }
        
        line_count++;
    }
    fclose(fp);
    
    // Update or add keys
    if (private_key_found) {
        free(lines[private_key_line]);
        char new_line[MAX_LINE_LEN];
        snprintf(new_line, sizeof(new_line), "my_private_key=%s\n", private_key_hex);
        lines[private_key_line] = strdup(new_line);
    } else {
        // Add after [global] line or at beginning
        // Simplified: add at end
        // We'll need to insert after [global] but for simplicity, append
    }
    
    if (public_key_found) {
        free(lines[public_key_line]);
        char new_line[MAX_LINE_LEN];
        snprintf(new_line, sizeof(new_line), "my_public_key=%s\n", public_key_hex);
        lines[public_key_line] = strdup(new_line);
    }
    
    // Write back to file
    fp = fopen(filename, "w");
    if (!fp) {
        // Cleanup
        for (size_t i = 0; i < line_count; i++) free(lines[i]);
        free(lines);
        return -1;
    }
    
    for (size_t i = 0; i < line_count; i++) {
        fputs(lines[i], fp);
        free(lines[i]);
    }
    
    // Add missing keys
    if (!private_key_found) {
        fprintf(fp, "my_private_key=%s\n", private_key_hex);
    }
    if (!public_key_found) {
        fprintf(fp, "my_public_key=%s\n", public_key_hex);
    }
    
    free(lines);
    fclose(fp);
    return 0;
}