//! Server config
use super::*;
use std::{
    net::SocketAddr,
    path::Path,
    io,
    borrow::Cow,
    num::NonZeroU64,
    error,
    fmt,
};
use tokio::{
    fs::OpenOptions,
    prelude::*,
    time::Duration,
    io::BufReader,
};
use ipfilt::IpFilter;

pub const DEFAULT_FILE_LOCATION: &'static str = "markov.toml";

#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Hash, Serialize, Deserialize)]
pub struct Config
{
    pub bindpoint: String,
    pub file: String,
    pub max_content_length: u64,
    pub max_gen_size: usize,
    pub save_interval_secs: Option<NonZeroU64>,
    pub trust_x_forwarded_for: bool,
    #[serde(default)]
    pub feed_bounds: String,
    #[serde(default)]
    pub filter: FilterConfig,
    #[serde(default)]
    pub writer: WriterConfig,
    #[serde(default)]
    pub mask: IpFilter,
}

#[derive(Debug, Default, Clone, PartialEq, Eq, PartialOrd, Hash, Serialize, Deserialize)]
pub struct FilterConfig
{
    #[serde(default)]
    inbound: String,
    #[serde(default)]
    outbound: String,
}

#[derive(Debug, Copy,  Clone, PartialEq, Eq, PartialOrd, Hash, Serialize, Deserialize)]
pub struct WriterConfig
{
    pub backlog: usize,
    pub internal_backlog: usize,
    pub capacity: usize,
    pub timeout_ms: Option<u64>,
    pub throttle_ms: Option<u64>,
}

impl Default for WriterConfig
{
    #[inline]
    fn default() -> Self
    {
	Self {
	    backlog: 32,
	    internal_backlog: 8,
	    capacity: 4,
	    timeout_ms: None,
	    throttle_ms: None,
	}
    }
}

impl WriterConfig
{
    fn create_settings(self, bounds: range::DynRange<usize>) -> handle::Settings
    {
	
	handle::Settings{
	    backlog: self.backlog,
	    internal_backlog: self.internal_backlog,
	    capacity: self.capacity,
	    timeout: self.timeout_ms.map(tokio::time::Duration::from_millis).unwrap_or(handle::DEFAULT_TIMEOUT),
	    throttle: self.throttle_ms.map(tokio::time::Duration::from_millis),
	    bounds,
	}
	
    }
}


impl FilterConfig
{
    fn get_inbound_filter(&self) -> sanitise::filter::Filter
    {
	let filt: sanitise::filter::Filter = self.inbound.parse().unwrap();
	if !filt.is_empty()
	{
	    info!("Loaded inbound filter: {:?}", filt.iter().collect::<String>());
	}
	filt
    }
    fn get_outbound_filter(&self) -> sanitise::filter::Filter
    {
	let filt: sanitise::filter::Filter = self.outbound.parse().unwrap();
	if !filt.is_empty()
	{
	    info!("Loaded outbound filter: {:?}", filt.iter().collect::<String>());
	}
	filt
    }
}

impl Default for Config
{
    #[inline]
    fn default() -> Self
    {
	Self {
	    bindpoint: SocketAddr::from(([127,0,0,1], 8001)).to_string(),
	    file: "chain.dat".to_owned(),
	    max_content_length: 1024 * 1024 * 4,
	    max_gen_size: 256,
	    save_interval_secs: Some(unsafe{NonZeroU64::new_unchecked(2)}),
	    trust_x_forwarded_for: false,
	    filter: Default::default(),
	    feed_bounds: "2..".to_owned(),
	    writer: Default::default(),
	    mask: Default::default(),
	}
    }
}

impl Config
{
    /// Try to generate a config cache for this instance.
    pub fn try_gen_cache(&self) -> Result<Cache, InvalidConfigError>
    {
	macro_rules! section {
	    ($name:literal, $expr:expr) => {
		match $expr {
		    Ok(v) => Ok(v),
		    Err(e) => Err(InvalidConfigError($name, Box::new(e))),
		}
	    }
	}
	use std::ops::RangeBounds;

	let feed_bounds = section!("feed_bounds", self.parse_feed_bounds()).and_then(|bounds| if bounds.contains(&0) {
		Err(InvalidConfigError("feed_bounds", Box::new(opaque_error!("Bounds not allowed to contains 0 (they were `{}`)", bounds))))
	    } else {
		Ok(bounds)
	    })?;
	Ok(Cache {
	    handler_settings: self.writer.create_settings(feed_bounds.clone()),
	    feed_bounds,
	    inbound_filter: self.filter.get_inbound_filter(),
	    outbound_filter: self.filter.get_outbound_filter(),
	})
    }
    /// Try to parse the `feed_bounds`
    fn parse_feed_bounds(&self) -> Result<range::DynRange<usize>, range::ParseError>
    {
	if self.feed_bounds.len() == 0 {
	    Ok(feed::DEFAULT_FEED_BOUNDS.into())
	} else {
	    self.feed_bounds.parse()
	}
    }
    pub fn save_interval(&self) -> Option<Duration>
    {
	self.save_interval_secs.map(|x| Duration::from_secs(x.into()))
    }
    pub async fn load(from: impl AsRef<Path>) -> io::Result<Self>
    {
	let file = OpenOptions::new()
	    .read(true)
	    .open(from).await?;

	let mut buffer= String::new();
	let reader = BufReader::new(file);
	let mut lines = reader.lines();
	while let Some(line) = lines.next_line().await? {
	    buffer.push_str(&line[..]);
	    buffer.push('\n');
	}
	toml::de::from_str(&buffer[..]).map_err(|e| io::Error::new(io::ErrorKind::InvalidInput, e))
    }

    pub async fn save(&self, to: impl AsRef<Path>) -> io::Result<()>
    {
	let config = toml::ser::to_string_pretty(self).map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
	let mut file = OpenOptions::new()
	    .write(true)
	    .create(true)
	    .truncate(true)
	    .open(to).await?;
	file.write_all(config.as_bytes()).await?;
	file.shutdown().await?;
	Ok(())
    }
}

/// Try to load config file specified by args, or default config file
pub fn load() -> impl futures::future::Future<Output =Option<Config>>
{
    load_args(std::env::args().skip(1))
}

async fn load_args<I: Iterator<Item=String>>(mut from: I) -> Option<Config>
{
    let place = if let Some(arg) = from.next() {
	trace!("File {:?} provided", arg);
	Cow::Owned(arg)
    } else {
	warn!("No config file provided. Using default location {:?}", DEFAULT_FILE_LOCATION);
	Cow::Borrowed(DEFAULT_FILE_LOCATION)
    };

    match Config::load(place.as_ref()).await {
	Ok(cfg) => {
	    info!("Loaded config file {:?}", place);
	    Some(cfg)
	},
	Err(err) => {
	    error!("Failed to load config file from {:?}: {}", place, err);
	    None
	},
    }
}

#[derive(Debug)]
pub struct InvalidConfigError(&'static str, Box<dyn error::Error+ 'static>);

impl InvalidConfigError
{
    pub fn field(&self) -> &str
    {
	&self.0[..]
    }
}

impl error::Error for InvalidConfigError
{
    fn source(&self) -> Option<&(dyn error::Error + 'static)> {
	Some(self.1.as_ref())
    }
}

impl fmt::Display for InvalidConfigError
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
    {
	write!(f,"failed to parse field `{}`: {}", self.0, self.1)
    }
}


/// Caches some parsed config arguments
#[derive(Clone, PartialEq)]
pub struct Cache
{
    pub feed_bounds: range::DynRange<usize>,
    pub inbound_filter: sanitise::filter::Filter,
    pub outbound_filter: sanitise::filter::Filter,
    pub handler_settings: handle::Settings,
}

impl fmt::Debug for Cache
{
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
    {
	f.debug_struct("Cache")
	    .field("feed_bounds", &self.feed_bounds)
	    .field("inbound_filter", &self.inbound_filter.iter().collect::<String>())
	    .field("outbound_filter", &self.outbound_filter.iter().collect::<String>())
	    .field("handler_settings", &self.handler_settings)
	    .finish()
    }
}