use std::mem::{self, MaybeUninit};

use chrono::prelude::*;
use failure::*;
use serde_json::{json, Value};

use proxmox::api::{api, Router, Permission};
use proxmox::tools::fs::{file_read_firstline, replace_file, CreateOptions};

use crate::api2::types::*;

fn read_etc_localtime() -> Result<String, Error> {
    // use /etc/timezone
    if let Ok(line) = file_read_firstline("/etc/timezone") {
        return Ok(line.trim().to_owned());
    }

    // otherwise guess from the /etc/localtime symlink
    let mut buf = MaybeUninit::<[u8; 64]>::uninit();
    let len = unsafe {
        libc::readlink(
            "/etc/localtime".as_ptr() as *const _,
            buf.as_mut_ptr() as *mut _,
            mem::size_of_val(&buf),
        )
    };
    if len <= 0 {
        bail!("failed to guess timezone");
    }
    let len = len as usize;
    let buf = unsafe {
        (*buf.as_mut_ptr())[len] = 0;
        buf.assume_init()
    };
    let link = std::str::from_utf8(&buf[..len])?;
    match link.rfind("/zoneinfo/") {
        Some(pos) => Ok(link[(pos + 10)..].to_string()),
        None => Ok(link.to_string()),
    }
}

#[api(
    input: {
        properties: {
            node: {
                schema: NODE_SCHEMA,
            },
        },
    },
    returns: {
        description: "Returns server time and timezone.",
        properties: {
            timezone: {
                schema: TIME_ZONE_SCHEMA,
            },
            time: {
                type: i64,
                description: "Seconds since 1970-01-01 00:00:00 UTC.",
                minimum: 1_297_163_644,
            },
            localtime: {
                type: i64,
                description: "Seconds since 1970-01-01 00:00:00 UTC. (local time)",
                minimum: 1_297_163_644,
            },
        }
    },
    access: {
        permission: &Permission::Anybody,
    },
)]
/// Read server time and time zone settings.
fn get_time(_param: Value) -> Result<Value, Error> {
    let datetime = Local::now();
    let offset = datetime.offset();
    let time = datetime.timestamp();
    let localtime = time + (offset.fix().local_minus_utc() as i64);

    Ok(json!({
        "timezone": read_etc_localtime()?,
        "time": time,
        "localtime": localtime,
    }))
}

#[api(
    protected: true,
    reload_timezone: true,
    input: {
        properties: {
            node: {
                schema: NODE_SCHEMA,
            },
            timezone: {
                schema: TIME_ZONE_SCHEMA,
            },
        },
    },
)]
/// Set time zone
fn set_timezone(
    timezone: String,
    _param: Value,
) -> Result<Value, Error> {
    let path = std::path::PathBuf::from(format!("/usr/share/zoneinfo/{}", timezone));

    if !path.exists() {
        bail!("No such timezone.");
    }

    replace_file("/etc/timezone", timezone.as_bytes(), CreateOptions::new())?;

    let _ = std::fs::remove_file("/etc/localtime");

    use std::os::unix::fs::symlink;
    symlink(path, "/etc/localtime")?;

    Ok(Value::Null)
}

pub const ROUTER: Router = Router::new()
    .get(&API_METHOD_GET_TIME)
    .put(&API_METHOD_SET_TIMEZONE);