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use anyhow::{anyhow,Context};
use std::ops::Deref;
use std::convert::AsRef;
use std::fmt::Debug;
use std::sync::Arc;
use std::fs;
use serde::de::Deserialize;
use tokio::process::Command;

use crate::local::CollarKey;

type E = anyhow::Error;

pub struct ParsedConfig {
  t : toml::Value,
  filename : String,
}

pub type Config = Arc<ParsedConfig>;

impl Deref for ParsedConfig {
  type Target = toml::Value;
  fn deref(&self) -> &toml::Value { &self.t }
}

pub const NO_MORE : [&str;0] = [];

const DEFAULT_KEY_FILE : &str = "/etc/tau.key";

pub trait Key : Debug {
  fn get<'t>(&self, t : &'t toml::Value) -> Option<&'t toml::value::Value>;
}
impl Key for str {
  fn get<'t>(&self, t : &'t toml::Value) -> Option<&'t toml::value::Value> {
    t.get(self)
  }
}
impl<K> Key for [&K] where K : Key + ?Sized {
  fn get<'t>(&self, t0 : &'t toml::Value) -> Option<&'t toml::value::Value> {
    let mut t = t0;
    for k in self { t = k.get(t)? }
    Some(t)
  }
}
impl<'s, R : Debug + AsRef<[&'s str]>> Key for R {
  fn get<'t>(&self, t : &'t toml::Value) -> Option<&'t toml::value::Value> {
    Key::get(self.as_ref(), t)
  }
}

//impl Key for [&str] {
//}

impl ParsedConfig {
  pub fn lookup<'l, K : Key + ?Sized, T : Deserialize<'l>>
    (&self, k : &K, def : T) -> Result<T,E>
  {
    let s = k.get(self);
    if s.is_none() { return Ok(def) }
    Ok( s.unwrap().clone().try_into()
        .context(format!("config key {:?}",k))? )
  }

  pub fn need<'l, K : Key + ?Sized, T : Deserialize<'l>>
    (&self, k : &K) -> Result<T,E>
  {
    Ok((||{
      let s = k.get(self).ok_or_else(|| anyhow!("missing config"))?;
      <Result<T,E>>::Ok(s.clone().try_into()?)
    })().context(format!("config key {:?}",&k))?)
  }

  fn command_from_strs<K : Key + ?Sized,
                       S : Debug + AsRef<str>, M : Debug + AsRef<str>>
                       (k : &K, cmd : &[S], more : &[M])
     -> Result<Command,E>
  {
    let l : Vec<&str> =
      cmd.iter().map(|s| s.as_ref())
      .chain( more.iter().map(|s| <M as AsRef<str>>::as_ref(s)) )
      .collect();
    println!("config: command for {:?}: {:?}", k, l);
    let mut c : Command = Command::new(
      l.first().ok_or_else(|| anyhow!("missing command") )?
    );
    c.args(l.iter().skip(1));
    <Result<Command,E>>::Ok(c)
  }

  pub fn command_general<K : Key + ?Sized,
                        S : Debug + AsRef<str>, M : Debug + AsRef<str>>
                        (&self, k : &K, def : &[S], more_args : &[M])
     -> Result<Command,E>
  {
    let c = (||{
      let l = k.get(self);
      if l.is_some() {
        let l : Vec<String> = l.unwrap().clone().try_into()?;
        Self::command_from_strs(k, &l,   more_args)
      } else {
        Self::command_from_strs(k, &def, more_args)
      }
    })().context(format!("command from config key {:?}",k))?;
    Ok(c)
  }

  pub fn command_simple<K : Key + ?Sized,
                        M : Debug + AsRef<str>>
                        (&self, k : &K, def : &str, more : &[M])
                         -> Result<Command,E> {
    self.command_general(k, &[def, &self.filename], more)
  }

  pub fn collar_key(&self) -> Result<CollarKey,E> {
    let key_file = self.lookup::<str, String>("key_file", DEFAULT_KEY_FILE.to_owned())?;
    let key = (||{
      let content = fs::read_to_string(&key_file)?;
      let key = content.trim().parse().context("parse key")?;
      <Result<CollarKey,E>>::Ok(key)
    })().context(format!("read key file {:?}",key_file))?;
    Ok(key)
  }
}

pub fn read() -> Result<Config, E> {
  let filename = std::env::args().nth(1)
    .ok_or_else(|| anyhow!("need config file arg"))?;
  let content = fs::read_to_string(&filename).context("config file")?;
  parse(&content, filename)
}

pub fn parse(content : &str, filename : String) -> Result<Config, E> {
  Ok(Arc::new( ParsedConfig{ t : content.parse()?, filename } ))
}