use anyhow::{anyhow, Context, Result};
use async_stream::stream;
use clap::Parser;
use encoding::{label::encoding_from_whatwg_label, EncoderTrap};
use std::{
    collections::BTreeMap,
    fmt::Display,
    path::{Path, PathBuf},
    str::FromStr,
};
use tokio::{
    fs::{self, File},
    io::{AsyncBufReadExt, BufReader},
};

use futures_core::stream::Stream;

pub(crate) type VarsMap = BTreeMap<String, String>;

#[derive(Debug, Clone, PartialEq)]
pub enum OpenSSLProviderArg {
    Internal,
    ExternalBin(String),
}

impl FromStr for OpenSSLProviderArg {
    type Err = anyhow::Error;
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s.to_ascii_lowercase().as_str() {
            "internal" => Ok(OpenSSLProviderArg::Internal),
            x => Ok(OpenSSLProviderArg::ExternalBin(x.to_string())),
        }
    }
}

impl Display for OpenSSLProviderArg {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            OpenSSLProviderArg::ExternalBin(x) => write!(f, "{}", x),
            _ => write!(f, "internal"),
        }
    }
}

#[derive(Parser)]
#[command(author, version, about, long_about = None)]
pub(crate) struct Args {
    /// new client name
    pub(crate) name: String,

    /// pki directory
    #[arg(short, long)]
    pub(crate) directory: Option<String>,

    /// client email
    #[arg(short, long)]
    pub(crate) email: Option<String>,

    /// files encoding
    #[arg(short = 'c', long)]
    pub(crate) encoding: Option<String>,

    /// keys subdir
    #[arg(long, default_value = "keys")]
    pub(crate) keys_dir: String,

    /// config subdir
    #[arg(long, default_value = "config")]
    pub(crate) config_dir: String,

    /// valid days
    #[arg(long, default_value = "3650")]
    pub(crate) days: u32,

    /// openssl binary or (internal)
    #[arg(long, short, default_value = "internal")]
    pub(crate) openssl: OpenSSLProviderArg,

    /// template file
    #[arg(long, default_value = "template.ovpn")]
    pub(crate) template_file: String,
}

pub(crate) struct AppConfig {
    pub(crate) encoding: String,
    pub(crate) req_days: u32,
    pub(crate) keys_subdir: String,
    pub(crate) config_subdir: String,
    pub(crate) template_file: String,
    pub(crate) openssl_default_cnf: String,
    pub(crate) openssl_cnf_env: String,
    pub(crate) ca_filename: String,
    pub(crate) default_email_domain: String,
    pub(crate) openssl: OpenSSLProviderArg,
    pub(crate) base_directory: String,
    pub(crate) email: String,
    pub(crate) name: String,
}

impl Default for AppConfig {
    fn default() -> Self {
        Self {
            encoding: "cp866".into(),
            req_days: 30650,
            keys_subdir: "keys".into(),
            config_subdir: "config".into(),
            template_file: "template.ovpn".into(),
            openssl_default_cnf: "openssl-1.0.0.cnf".into(),
            openssl_cnf_env: "KEY_CONFIG".into(),
            ca_filename: "ca.crt".into(),
            default_email_domain: "example.com".into(),
            openssl: OpenSSLProviderArg::Internal,
            base_directory: ".".into(),
            email: "name@example.com".into(),
            name: "user".into(),
        }
    }
}

impl From<&Args> for AppConfig {
    fn from(args: &Args) -> Self {
        let defaults = Self::default();

        let base_directory = args
            .directory
            .as_ref()
            .unwrap_or(&defaults.base_directory)
            .clone();
        let email = args.email.clone().unwrap_or(format!(
            "{}@{}",
            &args.name,
            defaults.default_email_domain.clone()
        ));
        let encoding = if let Some(enc) = args.encoding.clone() {
            enc.to_string()
        } else {
            defaults.encoding.clone()
        };
        let name = args.name.clone();
        let openssl = args.openssl.clone();
        let template_file = args.template_file.clone();
        let req_days = args.days;
        let keys_subdir = args.keys_dir.clone();
        let config_subdir = args.config_dir.clone();

        Self {
            base_directory,
            email,
            encoding,
            name,
            openssl,
            template_file,
            req_days,
            keys_subdir,
            config_subdir,
            ..defaults
        }
    }
}

pub(crate) async fn is_file_exist(filepath: &PathBuf) -> bool {
    let metadata = tokio::fs::metadata(&filepath).await;
    if metadata.is_err() {
        return false;
    }

    if !metadata.unwrap().is_file() {
        return false;
    }

    true
}

pub(crate) async fn read_file<'a, S, P>(filepath: P, encoding: S) -> Result<String>
where
    S: AsRef<str> + std::cmp::PartialEq<&'a str>,
    P: AsRef<Path>,
{
    let filepath = PathBuf::from(filepath.as_ref());
    if encoding == "utf8" {
        return Ok(fs::read_to_string(filepath).await?);
    }

    let enc = encoding_from_whatwg_label(encoding.as_ref()).ok_or(anyhow!("encoding not found"))?;

    let bytes = fs::read(filepath).await?;
    enc.decode(&bytes, encoding::DecoderTrap::Ignore)
        .map_err(|_| anyhow!("could not read file"))
}

pub(crate) async fn write_file(filepath: &PathBuf, text: String, encoding: &str) -> Result<()> {
    if encoding == "utf8" {
        return Ok(fs::write(filepath, text).await?);
    }

    let enc = encoding_from_whatwg_label(encoding).ok_or(anyhow!("encoding not found"))?;
    let mut bytes = Vec::new();
    enc.encode_to(&text, EncoderTrap::Ignore, &mut bytes)
        .map_err(|_| anyhow!("can't encode"))?;

    fs::write(filepath, bytes).await.context("can't write file")
}

pub(crate) async fn read_file_by_lines(
    filepath: &PathBuf,
    encoding: &str,
) -> Result<Box<dyn Stream<Item = String>>> {
    Ok(if encoding == "utf8" {
        let f = File::open(filepath).await?;
        let reader = BufReader::new(f);
        let mut lines = reader.lines();
        Box::new(stream! {
            while let Ok(Some(line)) = lines.next_line().await {
                yield line
            }
        })
    } else {
        let text = read_file(filepath, encoding).await?;
        Box::new(stream! {
            for line in text.lines() {
                yield line.to_string()
            }
        })
    })
}