use std::sync::{Arc, Mutex};

use anyhow::{Error};
use lazy_static::lazy_static;
use openssl::sha;
use regex::Regex;
use serde_json::{json, Value};

use proxmox::api::{api, ApiMethod, Router, RpcEnvironment, Permission};
use proxmox::tools::fs::{file_get_contents, replace_file, CreateOptions};
use proxmox::{IPRE, IPV4RE, IPV6RE, IPV4OCTET, IPV6H16, IPV6LS32};

use crate::api2::types::*;
use crate::config::acl::{PRIV_SYS_AUDIT, PRIV_SYS_MODIFY};

static RESOLV_CONF_FN: &str = "/etc/resolv.conf";

pub fn read_etc_resolv_conf() -> Result<Value, Error> {

    let mut result = json!({});

    let mut nscount = 0;

    let raw = file_get_contents(RESOLV_CONF_FN)?;

    result["digest"] = Value::from(proxmox::tools::digest_to_hex(&sha::sha256(&raw)));

    let data = String::from_utf8(raw)?;

    lazy_static! {
        static ref DOMAIN_REGEX: Regex = Regex::new(r"^\s*(?:search|domain)\s+(\S+)\s*").unwrap();
        static ref SERVER_REGEX: Regex = Regex::new(
            concat!(r"^\s*nameserver\s+(", IPRE!(),  r")\s*")).unwrap();
    }

    for line in data.lines() {

        if let Some(caps) = DOMAIN_REGEX.captures(&line) {
            result["search"] = Value::from(&caps[1]);
        } else if let Some(caps) = SERVER_REGEX.captures(&line) {
            nscount += 1;
            if nscount > 3 { continue };
            let nameserver = &caps[1];
            let id = format!("dns{}", nscount);
            result[id] = Value::from(nameserver);
        }
    }

    Ok(result)
}

#[api(
    protected: true,
    input: {
        description: "Update DNS settings.",
        properties: {
            node: {
                schema: NODE_SCHEMA,
            },
            search: {
                schema: SEARCH_DOMAIN_SCHEMA,
            },
            dns1: {
                optional: true,
                schema: FIRST_DNS_SERVER_SCHEMA,
            },
            dns2: {
                optional: true,
                schema: SECOND_DNS_SERVER_SCHEMA,
            },
            dns3: {
                optional: true,
                schema: THIRD_DNS_SERVER_SCHEMA,
            },
            digest: {
                optional: true,
                schema: PROXMOX_CONFIG_DIGEST_SCHEMA,
            },
        },
    },
    access: {
        permission: &Permission::Privilege(&[], PRIV_SYS_MODIFY, false),
    }
)]
/// Update DNS settings
fn update_dns(
    param: Value,
    _info: &ApiMethod,
    _rpcenv: &mut dyn RpcEnvironment,
) -> Result<Value, Error> {

    lazy_static! {
        static ref MUTEX: Arc<Mutex<usize>> = Arc::new(Mutex::new(0));
    }

    let _guard = MUTEX.lock();

    let search = crate::tools::required_string_param(&param, "search")?;

    let raw = file_get_contents(RESOLV_CONF_FN)?;
    let old_digest = proxmox::tools::digest_to_hex(&sha::sha256(&raw));

    if let Some(digest) = param["digest"].as_str() {
        crate::tools::assert_if_modified(&old_digest, &digest)?;
    }

    let old_data = String::from_utf8(raw)?;

    let mut data = format!("search {}\n", search);

    for opt in &["dns1", "dns2", "dns3"] {
        if let Some(server) = param[opt].as_str() {
            data.push_str(&format!("nameserver {}\n", server));
        }
    }

    // append other data
    lazy_static! {
        static ref SKIP_REGEX: Regex = Regex::new(r"^(search|domain|nameserver)\s+").unwrap();
    }
    for line in old_data.lines() {
        if SKIP_REGEX.is_match(line) { continue; }
        data.push_str(line);
        data.push('\n');
    }

    replace_file(RESOLV_CONF_FN, data.as_bytes(), CreateOptions::new())?;

    Ok(Value::Null)
}

#[api(
    input: {
        properties: {
            node: {
                schema: NODE_SCHEMA,
            },
        },
    },
    returns: {
        description: "Returns DNS server IPs and sreach domain.",
        type: Object,
        properties: {
            digest: {
                schema: PROXMOX_CONFIG_DIGEST_SCHEMA,
            },
            search: {
                optional: true,
                schema: SEARCH_DOMAIN_SCHEMA,
            },
            dns1: {
                optional: true,
                schema: FIRST_DNS_SERVER_SCHEMA,
            },
            dns2: {
                optional: true,
                schema: SECOND_DNS_SERVER_SCHEMA,
            },
            dns3: {
                optional: true,
                schema: THIRD_DNS_SERVER_SCHEMA,
            },
        },
    },
    access: {
        permission: &Permission::Privilege(&[], PRIV_SYS_AUDIT, false),
    }
)]
/// Read DNS settings.
fn get_dns(
    _param: Value,
    _info: &ApiMethod,
    _rpcenv: &mut dyn RpcEnvironment,
) -> Result<Value, Error> {

    read_etc_resolv_conf()
}

pub const ROUTER: Router = Router::new()
    .get(&API_METHOD_GET_DNS)
    .put(&API_METHOD_UPDATE_DNS);