// layer.rs

//

// Copyright 2020

//      Valentin Gatien-Baron,

//      Raphaël Gomès <rgomes@octobus.net>

//

// This software may be used and distributed according to the terms of the

// GNU General Public License version 2 or any later version.

use crate::utils::files::{

    get_bytes_from_path, get_path_from_bytes, read_whole_file,

};

use format_bytes::format_bytes;

use lazy_static::lazy_static;

use regex::bytes::Regex;

use std::collections::HashMap;

use std::io;

use std::path::{Path, PathBuf};

lazy_static! {

    static ref SECTION_RE: Regex = make_regex(r"^\[([^\[]+)\]");

    static ref ITEM_RE: Regex = make_regex(r"^([^=\s][^=]*?)\s*=\s*((.*\S)?)");

    /// Continuation whitespace

    static ref CONT_RE: Regex = make_regex(r"^\s+(\S|\S.*\S)\s*$");

    static ref EMPTY_RE: Regex = make_regex(r"^(;|#|\s*$)");

    static ref COMMENT_RE: Regex = make_regex(r"^(;|#)");

    /// A directive that allows for removing previous entries

    static ref UNSET_RE: Regex = make_regex(r"^%unset\s+(\S+)");

    /// A directive that allows for including other config files

    static ref INCLUDE_RE: Regex = make_regex(r"^%include\s+(\S|\S.*\S)\s*$");

}

/// All config values separated by layers of precedence.

/// Each config source may be split in multiple layers if `%include` directives

/// are used.

/// TODO detail the general precedence

#[derive(Clone)]

pub struct ConfigLayer {

    /// Mapping of the sections to their items

    sections: HashMap<Vec<u8>, ConfigItem>,

    /// All sections (and their items/values) in a layer share the same origin

    pub origin: ConfigOrigin,

    /// Whether this layer comes from a trusted user or group

    pub trusted: bool,

}

impl ConfigLayer {

    pub fn new(origin: ConfigOrigin) -> Self {

        ConfigLayer {

            sections: HashMap::new(),

            trusted: true, // TODO check

            origin,

        }

    }

    /// Add an entry to the config, overwriting the old one if already present.

    pub fn add(

        &mut self,

        section: Vec<u8>,

        item: Vec<u8>,

        value: Vec<u8>,

        line: Option<usize>,

    ) {

        self.sections

            .entry(section)

            .or_insert_with(|| HashMap::new())

            .insert(item, ConfigValue { bytes: value, line });

    }

    /// Returns the config value in `<section>.<item>` if it exists

    pub fn get(&self, section: &[u8], item: &[u8]) -> Option<&ConfigValue> {

        Some(self.sections.get(section)?.get(item)?)

    }

    pub fn is_empty(&self) -> bool {

        self.sections.is_empty()

    }

    /// Returns a `Vec` of layers in order of precedence (so, in read order),

    /// recursively parsing the `%include` directives if any.

    pub fn parse(src: &Path, data: &[u8]) -> Result<Vec<Self>, ConfigError> {

        let mut layers = vec![];

        // Discard byte order mark if any

        let data = if data.starts_with(b"\xef\xbb\xbf") {

            &data[3..]

        } else {

            data

        };

        // TODO check if it's trusted

        let mut current_layer = Self::new(ConfigOrigin::File(src.to_owned()));

        let mut lines_iter =

            data.split(|b| *b == b'\n').enumerate().peekable();

        let mut section = b"".to_vec();

        while let Some((index, bytes)) = lines_iter.next() {

            if let Some(m) = INCLUDE_RE.captures(&bytes) {

                let filename_bytes = &m[1];

                let filename_to_include = get_path_from_bytes(&filename_bytes);

            } else if let Some(_) = EMPTY_RE.captures(&bytes) {

            } else if let Some(m) = SECTION_RE.captures(&bytes) {

                section = m[1].to_vec();

            } else if let Some(m) = ITEM_RE.captures(&bytes) {

                let item = m[1].to_vec();

                let mut value = m[2].to_vec();

                loop {

                    match lines_iter.peek() {

                        None => break,

                        Some((_, v)) => {

                            if let Some(_) = COMMENT_RE.captures(&v) {

                            } else if let Some(_) = CONT_RE.captures(&v) {

                                value.extend(b"\n");

                                value.extend(&m[1]);

                            } else {

                                break;

                            }

                        }

                    };

                    lines_iter.next();

                }

                current_layer.add(

                    section.clone(),

                    item,

                    value,

                    Some(index + 1),

                );

            } else if let Some(m) = UNSET_RE.captures(&bytes) {

                if let Some(map) = current_layer.sections.get_mut(&section) {

                    map.remove(&m[1]);

                }

            } else {

                    origin: ConfigOrigin::File(src.to_owned()),

                    line: Some(index + 1),

                    bytes: bytes.to_owned(),

            }

        }

        if !current_layer.is_empty() {

            layers.push(current_layer);

        }

        Ok(layers)

    }

}

impl std::fmt::Debug for ConfigLayer {

    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {

        let mut sections: Vec<_> = self.sections.iter().collect();

        sections.sort_by(|e0, e1| e0.0.cmp(e1.0));

        for (section, items) in sections.into_iter() {

            let mut items: Vec<_> = items.into_iter().collect();

            items.sort_by(|e0, e1| e0.0.cmp(e1.0));

            for (item, config_entry) in items {

                writeln!(

                    f,

                    "{}",

                    String::from_utf8_lossy(&format_bytes!(

                        b"{}.{}={} # {}",

                        section,

                        item,

                        &config_entry.bytes,

                        &self.origin.to_bytes(),

                    ))

                )?

            }

        }

        Ok(())

    }

}

/// Mapping of section item to value.

/// In the following:

/// ```text

/// [ui]

/// paginate=no

/// ```

/// "paginate" is the section item and "no" the value.

pub type ConfigItem = HashMap<Vec<u8>, ConfigValue>;

#[derive(Clone, Debug, PartialEq)]

pub struct ConfigValue {

    /// The raw bytes of the value (be it from the CLI, env or from a file)

    pub bytes: Vec<u8>,

    /// Only present if the value comes from a file, 1-indexed.

    pub line: Option<usize>,

}

#[derive(Clone, Debug)]

pub enum ConfigOrigin {

    /// The value comes from a configuration file

    File(PathBuf),

    /// The value comes from the environment like `$PAGER` or `$EDITOR`

    Environment(Vec<u8>),

    /* TODO cli

     * TODO defaults (configitems.py)

     * TODO extensions

     * TODO Python resources?

     * Others? */

}

impl ConfigOrigin {

    /// TODO use some kind of dedicated trait?

    pub fn to_bytes(&self) -> Vec<u8> {

        match self {

            ConfigOrigin::File(p) => get_bytes_from_path(p),

            ConfigOrigin::Environment(e) => e.to_owned(),

        }

    }

}

#[derive(Debug, derive_more::From)]

pub enum ConfigError {

}

fn make_regex(pattern: &'static str) -> Regex {

    Regex::new(pattern).expect("expected a valid regex")

}

/// Includes are relative to the file they're defined in, unless they're

/// absolute.

fn read_include(

    old_src: &Path,

    new_src: &Path,

) -> (PathBuf, io::Result<Vec<u8>>) {

    if new_src.is_absolute() {

        (new_src.to_path_buf(), read_whole_file(&new_src))

    } else {

        let dir = old_src.parent().unwrap();

        let new_src = dir.join(&new_src);

        (new_src.to_owned(), read_whole_file(&new_src))

    }

}