// 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 "../lib/platform_compat.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <ctype.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <errno.h>
#include "../lib/mem.h"

#define PRIV_HEXKEY_LEN 65    // 32 bytes * 2 hex chars + null
#define PUB_HEXKEY_LEN 65    // 32 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) != 64) return 0;
    for (int i = 0; i < 64; 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 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;
}

// Смещение байта сразу после ']' заголовка секции "[name]" (регистронезависимо), -1 если нет.
static long find_section_header(const char *buf, size_t buf_len, const char *name) {
    size_t name_len = strlen(name);
    size_t i = 0;
    while (i < buf_len) {
        if (buf[i] == '[' && i + name_len + 2 <= buf_len &&
            strncasecmp(buf + i + 1, name, name_len) == 0 && buf[i + name_len + 1] == ']') {
            return (long)(i + name_len + 2);
        }
        const char *nl = memchr(buf + i, '\n', buf_len - i);
        if (!nl) break;
        i = (size_t)(nl - buf) + 1;
    }
    return -1;
}

// Смещение строки, начинающейся с "option=", в диапазоне [start, end), -1 если нет.
static long find_option_in_range(const char *buf, size_t start, size_t end, const char *option) {
    size_t olen = strlen(option);
    size_t i = start;
    while (i < end) {
        if (i + olen <= end && strncmp(buf + i, option, olen) == 0 && buf[i + olen] == '=') {
            return (long)i;
        }
        const char *nl = memchr(buf + i, '\n', end - i);
        if (!nl) break;
        i = (size_t)(nl - buf) + 1;
    }
    return -1;
}

// Заменить строку option=value внутри секции [section], либо вставить её сразу после
// строки заголовка секции (без пустых строк). Возвращает 0 / -1.
static int insert_or_replace_in_section(char **buf, size_t *buf_len, size_t *buf_capacity,
                                        const char *section, const char *option, const char *value) {
    if (!buf || !*buf || !buf_len || !buf_capacity || !section || !option || !value) return -1;

    long hdr_off = find_section_header(*buf, *buf_len, section);
    if (hdr_off < 0) return -1;
    size_t sec_start = (size_t)hdr_off;

    char *next_sec = memchr(*buf + sec_start, '[', *buf_len - sec_start);
    size_t sec_end = next_sec ? (size_t)(next_sec - *buf) : *buf_len;

    long opt_off = find_option_in_range(*buf, sec_start, sec_end, option);

    if (opt_off >= 0) {
        size_t opos = (size_t)opt_off;
        char *nl = memchr(*buf + opos, '\n', sec_end - opos);
        int has_trailing_nl = (nl != NULL);
        size_t line_end = nl ? (size_t)(nl - *buf) + 1 : sec_end;
        size_t old_len = line_end - opos;

        char new_line[MAX_LINE_LEN];
        int new_len = snprintf(new_line, sizeof(new_line), "%s=%s%s", option, value, has_trailing_nl ? "\n" : "");
        if (new_len <= 0 || new_len >= (int)sizeof(new_line)) return -1;

        long len_diff = (long)new_len - (long)old_len;
        if ((long)*buf_len + len_diff + 1 > (long)*buf_capacity) {
            *buf_capacity = *buf_len + len_diff + 1024;
            char *new_buf = u_realloc(*buf, *buf_capacity);
            if (!new_buf) return -1;
            *buf = new_buf;
            hdr_off = find_section_header(*buf, *buf_len, section);
            if (hdr_off < 0) return -1;
            sec_start = (size_t)hdr_off;
            next_sec = memchr(*buf + sec_start, '[', *buf_len - sec_start);
            sec_end = next_sec ? (size_t)(next_sec - *buf) : *buf_len;
            opt_off = find_option_in_range(*buf, sec_start, sec_end, option);
            if (opt_off < 0) return -1;
            opos = (size_t)opt_off;
            nl = memchr(*buf + opos, '\n', sec_end - opos);
            has_trailing_nl = (nl != NULL);
            line_end = nl ? (size_t)(nl - *buf) + 1 : sec_end;
        }

        memmove(*buf + opos + new_len, *buf + line_end, *buf_len - line_end + 1);
        memcpy(*buf + opos, new_line, new_len);
        *buf_len += len_diff;
    } else {
        size_t ins = sec_start;
        int need_leading_nl = 0;
        if (ins < *buf_len && (*buf)[ins] == '\n') {
            ins += 1;
        } else {
            need_leading_nl = 1;
        }

        char new_line[MAX_LINE_LEN];
        int new_len = snprintf(new_line, sizeof(new_line), "%s%s=%s\n", need_leading_nl ? "\n" : "", option, value);
        if (new_len <= 0 || new_len >= (int)sizeof(new_line)) return -1;

        if (*buf_len + (size_t)new_len + 1 > *buf_capacity) {
            *buf_capacity = *buf_len + (size_t)new_len + 1024;
            char *new_buf = u_realloc(*buf, *buf_capacity);
            if (!new_buf) return -1;
            *buf = new_buf;
            hdr_off = find_section_header(*buf, *buf_len, section);
            if (hdr_off < 0) return -1;
            ins = (size_t)hdr_off;
            need_leading_nl = 0;
            if (ins < *buf_len && (*buf)[ins] == '\n') {
                ins += 1;
            } else {
                need_leading_nl = 1;
            }
            new_len = snprintf(new_line, sizeof(new_line), "%s%s=%s\n", need_leading_nl ? "\n" : "", option, value);
            if (new_len <= 0 || new_len >= (int)sizeof(new_line)) return -1;
        }

        memmove(*buf + ins + new_len, *buf + ins, *buf_len - ins + 1);
        memcpy(*buf + ins, new_line, new_len);
        *buf_len += new_len;
    }
    return 0;
}

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) {
        // Determine end of old line (1 byte after \n or end of buffer)
        char *nl = strchr(opt_pos, '\n');
        int has_trailing_nl = (nl != NULL);
        char *line_end = nl ? nl + 1 : *buf + *buf_len;

        // Prepare new line
        char new_line[MAX_LINE_LEN];
        int new_len;
        if (has_trailing_nl) {
            new_len = snprintf(new_line, sizeof(new_line), "%s=%s\n", option, value);
        } else {
            new_len = snprintf(new_line, sizeof(new_line), "%s=%s", 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;
        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 = u_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;
            nl = strchr(opt_pos, '\n');
            has_trailing_nl = (nl != NULL);
            line_end = nl ? nl + 1 : *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, '[');
        int need_leading_nl = 0;

        if (!insert_pos) {
            insert_pos = *buf + *buf_len;
            if (*buf_len > 0 && (*buf)[*buf_len - 1] != '\n')
                need_leading_nl = 1;
        } 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;
        if (need_leading_nl)
            new_len = snprintf(new_line, sizeof(new_line), "\n%s=%s\n", option, value);
        else
            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 = u_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, '[');
            need_leading_nl = 0;

            if (!insert_pos) {
                insert_pos = *buf + *buf_len;
                if (*buf_len > 0 && (*buf)[*buf_len - 1] != '\n')
                    need_leading_nl = 1;
            } 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) {
    // ── Read config file into memory (single open) ──
    FILE *fp = fopen(filename, "rb");
    char *file_buf = NULL;
    size_t file_size = 0;
    struct utun_config *config = NULL;

    if (fp) {
        fseek(fp, 0, SEEK_END); long fsz = ftell(fp); fseek(fp, 0, SEEK_SET);
        if (fsz < 0) { fclose(fp); return -1; }
        file_size = (size_t)fsz;
        file_buf = u_malloc(file_size + 1);
        if (!file_buf || fread(file_buf, 1, file_size, fp) != file_size) { u_free(file_buf); fclose(fp); return -1; }
        file_buf[file_size] = '\0';
        fclose(fp);
        config = parse_config_from_buf(file_buf, file_size, filename);
        if (!config) { DEBUG_ERROR(DEBUG_CATEGORY_CONFIG, "Failed to parse config from buffer: %s", filename); u_free(file_buf); return -1; }
    } else {
        // No file — create minimal config
        DEBUG_WARN(DEBUG_CATEGORY_CONFIG, "Config file not found, creating new: %s (errno=%d)", filename, errno);
        config = u_calloc(1, sizeof(struct utun_config));
        if (!config) return -1;
        config->global.my_node_id = 0;
        config->global.my_private_key_hex[0] = '\0';
        config->global.my_public_key_hex[0] = '\0';
        config->global.name[0] = '\0';
        config->global.keepalive_timeout = 2000;
        config->global.keepalive_interval = 200;
        config->global.keepalive_adaptive = 1;
        config->global.bbr_max_cwnd = 1048576;
    }

    struct global_config *global = &config->global;

    DEBUG_DEBUG(DEBUG_CATEGORY_CONFIG, "Checking config - priv_key='%s' (len=%zu), pub_key='%s' (len=%zu), node_id=%016llx",
           global->my_private_key_hex[0] ? global->my_private_key_hex : "NULL",
           global->my_private_key_hex[0] ? strlen(global->my_private_key_hex) : 0,
           global->my_public_key_hex[0] ? global->my_public_key_hex : "NULL",
           global->my_public_key_hex[0] ? strlen(global->my_public_key_hex) : 0,
           (unsigned long long)global->my_node_id);

    int need_priv_key = !is_valid_priv_key(global->my_private_key_hex);
    int need_pub_key  = 0;
    int need_node_id  = 0;
    char new_priv_key[PRIV_HEXKEY_LEN] = {0};
    char new_pub_key[PUB_HEXKEY_LEN] = {0};
    uint64_t new_node_id = 0;
    uint8_t priv_bin[SC_PRIVKEY_SIZE];

    // ── Step 1: ensure valid privkey ──
    if (need_priv_key) {
        DEBUG_WARN(DEBUG_CATEGORY_CONFIG, "Generating NEW keypair — private key was invalid/missing in %s", filename);
        struct SC_MYKEYS mykeys;
        if (sc_generate_keypair(&mykeys) != SC_OK) { free_config(config); u_free(file_buf); return -1; }
        bytes_to_hex(mykeys.private_key, SC_PRIVKEY_SIZE, new_priv_key, sizeof(new_priv_key));
        memcpy(priv_bin, mykeys.private_key, SC_PRIVKEY_SIZE);
    } else {
        for (int i = 0; i < SC_PRIVKEY_SIZE; i++) {
            unsigned int byte;
            if (sscanf(global->my_private_key_hex + i * 2, "%2x", &byte) != 1) { free_config(config); u_free(file_buf); return -1; }
            priv_bin[i] = (uint8_t)byte;
        }
        bytes_to_hex(priv_bin, SC_PRIVKEY_SIZE, new_priv_key, sizeof(new_priv_key));
    }

    // ── Step 2: derive pubkey from privkey ──
    uint8_t pub_bin[SC_PUBKEY_SIZE];
    if (sc_compute_public_key_from_private(priv_bin, pub_bin) != SC_OK) { free_config(config); u_free(file_buf); return -1; }
    bytes_to_hex(pub_bin, SC_PUBKEY_SIZE, new_pub_key, sizeof(new_pub_key));
    if (!is_valid_pub_key(global->my_public_key_hex) || strcmp(global->my_public_key_hex, new_pub_key) != 0) {
        need_pub_key = 1;
        DEBUG_WARN(DEBUG_CATEGORY_CONFIG, "Pubkey mismatch (or missing), fixing: config=%s derived=%s",
                   global->my_public_key_hex[0] ? global->my_public_key_hex : "NULL", new_pub_key);
    }

    // ── Step 3: derive node_id from pubkey ──
    new_node_id = sc_derive_node_id_from_pubkey(pub_bin);
    if (!is_valid_node_id(global->my_node_id) || global->my_node_id != new_node_id) {
        need_node_id = 1;
        DEBUG_WARN(DEBUG_CATEGORY_CONFIG, "Node_id mismatch (or missing), fixing: config=%016llx derived=%016llx file=%s",
                   (unsigned long long)global->my_node_id, (unsigned long long)new_node_id, filename);
    }

    // ── Step 4: reality-камуфляж — private_key и short_ids при enabled=1 ──
    int need_reality_priv = 0, need_reality_ids = 0;
    char new_reality_priv_hex[REALITY_AUTH_KEY_SIZE * 2 + 1] = {0};
    char new_short_ids_str[4 * (REALITY_SHORT_ID_SIZE * 2) + 4] = {0};

    if (global->reality.enabled) {
        if (!global->reality.has_private_key) {
            need_reality_priv = 1;
            DEBUG_WARN(DEBUG_CATEGORY_CONFIG, "Reality private_key missing, generating new one in %s", filename);
            uint8_t rpriv[REALITY_AUTH_KEY_SIZE], rpub[REALITY_AUTH_KEY_SIZE];
            if (reality_generate_keypair(rpriv, rpub) != REALITY_OK) { free_config(config); u_free(file_buf); return -1; }
            bytes_to_hex(rpriv, REALITY_AUTH_KEY_SIZE, new_reality_priv_hex, sizeof(new_reality_priv_hex));
        }
        if (global->reality.short_id_count == 0) {
            need_reality_ids = 1;
            DEBUG_WARN(DEBUG_CATEGORY_CONFIG, "Reality short_ids missing, generating 4 ids in %s", filename);
            char *p = new_short_ids_str;
            size_t remain = sizeof(new_short_ids_str);
            for (int i = 0; i < 4; i++) {
                uint8_t sid[REALITY_SHORT_ID_SIZE];
                if (random_bytes(sid, sizeof(sid)) != 0) { free_config(config); u_free(file_buf); return -1; }
                char hex[REALITY_SHORT_ID_SIZE * 2 + 1];
                bytes_to_hex(sid, REALITY_SHORT_ID_SIZE, hex, sizeof(hex));
                int w = snprintf(p, remain, "%s%s", i ? "," : "", hex);
                if (w < 0 || (size_t)w >= remain) { free_config(config); u_free(file_buf); return -1; }
                p += w; remain -= (size_t)w;
            }
        }
    }

    DEBUG_DEBUG(DEBUG_CATEGORY_CONFIG, "Validation results - need_priv_key=%d, need_pub_key=%d, need_node_id=%d, need_reality_priv=%d, need_reality_ids=%d",
           need_priv_key, need_pub_key, need_node_id, need_reality_priv, need_reality_ids);

    if (!need_priv_key && !need_pub_key && !need_node_id && !need_reality_priv && !need_reality_ids) {
        free_config(config); u_free(file_buf); return 0;
    }

    char cfg_name[MAX_CONN_NAME_LEN]; snprintf(cfg_name, sizeof(cfg_name), "%s", global->name[0] ? global->name : "utun");

    free_config(config);

    char node_id_hex[HEXNODEID_LEN + 1];
    snprintf(node_id_hex, sizeof(node_id_hex), "%016llx", (unsigned long long)new_node_id);

    // ── Modify/create config buffer ──
    char *work_buf = NULL; size_t work_len = 0; size_t buf_capacity = 0;
    int is_new_file = (!file_buf || !file_size);

    if (is_new_file) {
        buf_capacity = 2048;
        work_buf = u_malloc(buf_capacity);
        if (!work_buf) { u_free(file_buf); return -1; }
        work_len = (size_t)snprintf(work_buf, buf_capacity,
            "[global]\nmy_node_name=%s\nmy_private_key=%s\nmy_public_key=%s\nmy_node_id=%s\n",
            cfg_name, new_priv_key, new_pub_key, node_id_hex);
        u_free(file_buf); file_buf = NULL;
    } else {
        buf_capacity = file_size + 1024;
        work_buf = u_malloc(buf_capacity);
        if (!work_buf) { u_free(file_buf); return -1; }
        memcpy(work_buf, file_buf, file_size + 1); /* Helpers use strchr; preserve the terminating NUL. */
        work_len = file_size;
        u_free(file_buf); file_buf = NULL;
    }

    int ret = 0;

    if (!is_new_file) {
        int write_keys = (need_priv_key || need_pub_key || need_node_id);

        if (need_node_id) {
            DEBUG_WARN(DEBUG_CATEGORY_CONFIG, "Writing my_node_id=%s to %s", node_id_hex, filename);
            if (insert_or_replace_option(&work_buf, &work_len, &buf_capacity, "my_node_id", node_id_hex) < 0) ret = -1;
        }
        if (write_keys && ret == 0) {
            DEBUG_WARN(DEBUG_CATEGORY_CONFIG, "Writing my_private_key to %s", filename);
            if (insert_or_replace_option(&work_buf, &work_len, &buf_capacity, "my_private_key", new_priv_key) < 0) ret = -1;
        }
        if (write_keys && ret == 0) {
            DEBUG_WARN(DEBUG_CATEGORY_CONFIG, "Writing my_public_key to %s", filename);
            if (insert_or_replace_option(&work_buf, &work_len, &buf_capacity, "my_public_key", new_pub_key) < 0) ret = -1;
        }
        if (need_reality_ids && ret == 0) {
            DEBUG_WARN(DEBUG_CATEGORY_CONFIG, "Writing reality short_ids to %s", filename);
            if (insert_or_replace_in_section(&work_buf, &work_len, &buf_capacity, "reality", "short_ids", new_short_ids_str) < 0) ret = -1;
        }
        if (need_reality_priv && ret == 0) {
            DEBUG_WARN(DEBUG_CATEGORY_CONFIG, "Writing reality private_key to %s", filename);
            if (insert_or_replace_in_section(&work_buf, &work_len, &buf_capacity, "reality", "private_key", new_reality_priv_hex) < 0) ret = -1;
        }
    }

    if (ret == 0 && work_buf) {
        if (write_mem_to_file(filename, work_buf, work_len) < 0) {
            DEBUG_ERROR(DEBUG_CATEGORY_CONFIG, "Failed to write updated config file: %s", filename);
            ret = -1;
        } else {
            DEBUG_WARN(DEBUG_CATEGORY_CONFIG, "Config file updated: %s (gen_priv=%d gen_pub=%d gen_nodeid=%d gen_reality_priv=%d gen_reality_ids=%d)", filename, need_priv_key, need_pub_key, need_node_id, need_reality_priv, need_reality_ids);
        }
    }
    u_free(work_buf);
    return ret;
}