/* This file is part of DarkFi (https://dark.fi)
 *
 * Copyright (C) 2020-2022 Dyne.org foundation
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

use std::{
    env,
    ffi::{CStr, OsString},
    fs, mem,
    os::unix::prelude::OsStringExt,
    path::{Path, PathBuf},
    ptr,
};

use crate::{Error, Result};

/// Returns the path to the user's home directory.
/// Use `$HOME`, fallbacks to `libc::getpwuid_r`, otherwise `None`.
pub fn home_dir() -> Option<PathBuf> {
    env::var_os("HOME")
        .and_then(|h| if h.is_empty() { None } else { Some(h) })
        .or_else(|| unsafe { home_fallback() })
        .map(PathBuf::from)
}

/// Get the home directory from the passwd entry of the current user using
/// `getpwuid_r(3)`. If it manages, returns an `OsString`, otherwise returns `None`.
unsafe fn home_fallback() -> Option<OsString> {
    let amt = match libc::sysconf(libc::_SC_GETPW_R_SIZE_MAX) {
        n if n < 0 => 512 as usize,
        n => n as usize,
    };

    let mut buf = Vec::with_capacity(amt);
    let mut passwd: libc::passwd = mem::zeroed();
    let mut result = ptr::null_mut();

    let r = libc::getpwuid_r(
        libc::getuid(),
        &mut passwd,
        buf.as_mut_ptr(),
        buf.capacity(),
        &mut result,
    );

    match r {
        0 if !result.is_null() => {
            let ptr = passwd.pw_dir as *const _;
            let bytes = CStr::from_ptr(ptr).to_bytes();
            if bytes.is_empty() {
                return None
            }

            Some(OsStringExt::from_vec(bytes.to_vec()))
        }

        _ => None,
    }
}

/// Returns `$XDG_CONFIG_HOME`, `$HOME/.config`, or `None`.
pub fn config_dir() -> Option<PathBuf> {
    env::var_os("XDG_CONFIG_HOME")
        .and_then(is_absolute_path)
        .or_else(|| home_dir().map(|h| h.join(".config")))
}

fn is_absolute_path(path: OsString) -> Option<PathBuf> {
    let path = PathBuf::from(path);
    if path.is_absolute() {
        Some(path)
    } else {
        None
    }
}

pub fn expand_path(path: &str) -> Result<PathBuf> {
    let ret: PathBuf;

    if path.starts_with("~/") {
        if let Some(homedir) = home_dir() {
            let remains = PathBuf::from(path.strip_prefix("~/").unwrap());
            ret = [homedir, remains].iter().collect();
        } else {
            panic!("Could not fetch path for home directory");
        }
    } else if path.starts_with('~') {
        if let Some(homedir) = home_dir() {
            ret = homedir
        } else {
            panic!("Could not fetch path for home directory");
        }
    } else {
        ret = PathBuf::from(path);
    }

    Ok(ret)
}

/// Join a path with `config_dir()/darkfi`.
pub fn join_config_path(file: &Path) -> Result<PathBuf> {
    let mut path = PathBuf::new();
    let dfi_path = Path::new("darkfi");

    if let Some(v) = config_dir() {
        path.push(v);
    }

    path.push(dfi_path);
    path.push(file);

    Ok(path)
}

pub fn get_config_path(arg: Option<String>, fallback: &str) -> Result<PathBuf> {
    if let Some(a) = arg {
        expand_path(&a)
    } else {
        join_config_path(&PathBuf::from(fallback))
    }
}

pub fn load_keypair_to_str(path: PathBuf) -> Result<String> {
    if Path::new(&path).exists() {
        let key = fs::read(&path)?;
        let str_buff = std::str::from_utf8(&key)?;
        Ok(str_buff.to_string())
    } else {
        println!("Could not parse keypair path");
        Err(Error::KeypairPathNotFound)
    }
}