//! This module provides the [`FoldList`](::folds::FoldList) struct to
//! manage folds in a buffer. It carries both level 1 folds as well as level 2
//! folds (i.e. folds that contain folds of level 1). All functions that
//! insert/remove/modify folds operate on level 1 folds, the only thing to be
//! done for the level 2 folds is regenerating them in full from the level 1
//! folds.
//!
//! Example usage:
//!
//! ```
//! # use nvimpam_lib::folds::FoldList;
//! # use nvimpam_lib::card::keyword::Keyword;
//! let mut foldlist = FoldList::new();
//! foldlist
//!   .checked_insert(1, 2, Keyword::Node)
//!   .map_err(|e| println!("{}", e));
//! assert!(foldlist.remove(2, 3).is_err());
//! assert!(foldlist.remove(1, 2).is_ok());
//! ```
use std::collections::{btree_map::Entry, BTreeMap};

use failure::{self, Error, ResultExt};

use neovim_lib::{Neovim, NeovimApi, Value};

use itertools::Itertools;

use card::keyword::Keyword;
use lines::{Line, ParsedLine};
use nocommentiter::CommentLess;

macro_rules! unwrap_or_ok {
  ($option:expr) => {
    match $option {
      None => return Ok(()),
      Some(t) => t,
    }
  };
  ($option:expr, $ret:expr) => {
    match $option {
      None => return Ok($ret),
      Some(t) => t,
    }
  };
}

/// Holds the fold data of the buffer. A fold has the following data:
/// Linenumbers start, end (indexed from 0), and a
/// [Keyword](::card::Keyword).
#[derive(Default, Debug)]
pub struct FoldList {
  /// List of folds, keyed by [start, end], valued by
  /// [`Keyword`](::card::keyword::Keyword), sorted
  /// lexicographically on [start, end] (linenumbers starting at 0).
  folds: BTreeMap<[u64; 2], Keyword>,
  /// List of level 2 folds (i.e. containing level 1 folds), keyed by
  /// [start, end], valued by [`Keyword`](::card::keyword::Keyword), sorted
  /// lexicographically on [start, end] (linenumbers starting at 0).
  folds_level2: BTreeMap<[u64; 2], Keyword>,
  /// List of Strings to show as foldtext for level 1 folds, keyed by
  /// [start, end] (linenumbers starting at 0).
  fold_texts: BTreeMap<[u64; 2], String>,
  /// List of Strings to show as foldtext for level 2 folds, keyed by
  /// [start, end] (linenumbers starting at 0).
  fold_texts_level2: BTreeMap<[u64; 2], String>,
}

impl FoldList {
  /// Create a new FoldList. There does not seem to
  /// be a way to create one with a predetermined capacity.
  pub fn new() -> FoldList {
    FoldList {
      folds: BTreeMap::new(),
      folds_level2: BTreeMap::new(),
      fold_texts: BTreeMap::new(),
      fold_texts_level2: BTreeMap::new(),
    }
  }

  /// Clear FoldList, by clearing the BTreeMap's individually
  pub fn clear(&mut self) {
    self.folds.clear();
    self.folds_level2.clear();
    self.fold_texts.clear();
    self.fold_texts_level2.clear();
  }

  /// Insert a level 1 fold `([start, end], Keyword)` into the FoldList.
  /// Returns an error if that fold is already in the list. In that case,
  /// it needs to be [removed](struct.FoldList.html#method.remove) beforehand.
  fn insert(&mut self, start: u64, end: u64, kw: Keyword) -> Result<(), Error> {
    match self.folds.entry([start, end]) {
      Entry::Occupied(_) => {
        return Err(failure::err_msg("Fold already in foldlist!"))
      }
      Entry::Vacant(entry) => {
        entry.insert(kw);
      }
    }
    match self.fold_texts.entry([start, end]) {
      Entry::Occupied(_) => {
        return Err(failure::err_msg("Foldtext already in fold_texts!"))
      }
      Entry::Vacant(entry) => {
        entry.insert(format!(" {} lines: {:?} ", end - start + 1, kw));
      }
    }
    Ok(())
  }

  /// Insert a level 1 fold `([start, end], Keyword)` into the FoldList. If
  /// `end < start`, we silently return.  Otherwise, we call the internal
  /// insert function that returns an error if the fold is already in the
  /// list. In that case, it needs to be
  /// [removed](struct.FoldList.html#method.remove)
  /// beforehand.
  pub fn checked_insert(
    &mut self,
    start: u64,
    end: u64,
    kw: Keyword,
  ) -> Result<(), Error> {
    if start <= end {
      self.insert(start, end, kw)?
    }
    Ok(())
  }

  /// Remove a level 1 fold [start, end] from the foldlist. Only checks if the
  /// fold is in the FoldList, and returns an error otherwise.
  pub fn remove(&mut self, start: u64, end: u64) -> Result<(), Error> {
    self
      .folds
      .remove(&[start, end])
      .ok_or_else(|| failure::err_msg("Could not remove fold from foldlist"))?;
    self
      .fold_texts
      .remove(&[start, end])
      .ok_or_else(|| failure::err_msg("Could not remove fold from foldlist"))?;
    Ok(())
  }

  /// Remove all the entries from the FoldList, and iterate over lines to
  /// populate it with new ones. Then recreate the [level 2
  /// folds](::folds::FoldList::folds_level2).
  pub fn recreate_all(
    &mut self,
    keywords: &[Option<Keyword>],
    lines: &[Line],
  ) -> Result<(), Error> {
    self.clear();
    self.add_folds(keywords, lines)?;
    self.recreate_level2()
  }

  /// Recreate the level 2 folds from the level 1 folds. If there's no or one
  /// level 1 fold, `Ok(())` is returned.
  fn recreate_level2(&mut self) -> Result<(), Error> {
    self.folds_level2.clear();

    if self.folds.len() < 2 {
      return Ok(());
    }

    let grouped = self.folds.iter().group_by(|(_, &kw)| kw);

    for (kw, mut group) in &grouped {
      let mut group = group.enumerate();
      let firstfold = group.next().expect("Empty group from group_by!").1;
      let (nr, lastfold) = match group.last() {
        None => continue, // only 1 fold in group
        Some((i, e)) => (i, e),
      };

      let firstline = firstfold.0[0];
      let lastline = lastfold.0[1];

      if firstline < lastline {
        match self.folds_level2.entry([firstline, lastline]) {
          Entry::Occupied(_) => {
            return Err(failure::err_msg("Fold already in foldlist_level2!"))
          }
          Entry::Vacant(entry) => {
            entry.insert(kw);
          }
        }
        match self.fold_texts_level2.entry([firstline, lastline]) {
          Entry::Occupied(_) => {
            return Err(failure::err_msg("Foldtext already in fold_texts!"))
          }
          Entry::Vacant(entry) => {
            entry.insert(format!(" {} {:?}s ", nr + 1, kw));
          }
        }
      }
    }
    Ok(())
  }

  /// Delete all folds in nvim, and create the ones from the FoldList.
  pub fn resend_all(&self, nvim: &mut Neovim) -> Result<(), Error> {
    let luafn = "require('nvimpam').update_folds(...)";
    let mut luaargs = vec![];

    for (range, text) in self.fold_texts.iter().chain(&self.fold_texts_level2) {
      luaargs.push(Value::from(vec![
        Value::from(range[0] + 1),
        Value::from(range[1] + 1),
        Value::from(text.to_string()),
      ]));
    }

    nvim
      .execute_lua(luafn, vec![Value::from(luaargs)])
      .context("Execute lua failed")?;

    Ok(())
  }

  /// Copy the elements of a FoldList of the given level into a Vec, containing
  /// the tuples (start, end, Keyword)
  pub fn to_vec(&self, level: u8) -> Vec<(u64, u64, Keyword)> {
    if level == 1 {
      self.folds.iter().map(|(r, k)| (r[0], r[1], *k)).collect()
    } else if level == 2 {
      self
        .folds_level2
        .iter()
        .map(|(r, k)| (r[0], r[1], *k))
        .collect()
    } else {
      unimplemented!()
    }
  }

  /// Parse an array of `Option<Keyword>`s into a
  /// [`FoldList`](::folds::FoldList). The foldlist is cleared as a first step.
  ///
  /// Creates only level 1 folds. Depending on the
  /// [`ownfold`](::card::Card::ownfold) parameter in the
  /// definition of the card in the [carddata](::carddata) module, each card
  /// will be in an own fold, or several adjacent (modulo comments) cards will
  /// be subsumed into a fold.
  pub fn add_folds(
    &mut self,
    keywords: &[Option<Keyword>],
    lines: &[Line],
  ) -> Result<(), Error> {
    debug_assert!(keywords.len() == lines.len());
    let mut li = keywords
      .iter()
      .zip(lines)
      .enumerate()
      .map(ParsedLine::from)
      .remove_comments();

    let mut foldstart;
    let mut foldend;
    let mut foldkw;
    let mut skipped;

    let mut nextline = unwrap_or_ok!(li.skip_to_next_keyword());

    loop {
      foldkw = nextline.keyword;
      foldstart = nextline.number;
      skipped = li.skip_fold(nextline);

      // The latter only happens when a file ends after the only line of a card
      foldend = skipped.skip_end.unwrap_or_else(|| lines.len() - 1);

      self.checked_insert(foldstart as u64, foldend as u64, *foldkw)?;

      if let Some(Some(kl)) =
        skipped.nextline.map(|pl| pl.try_into_keywordline())
      {
        nextline = kl;
      } else {
        nextline = unwrap_or_ok!(li.skip_to_next_keyword());
      }
    }
  }
}

#[cfg(test)]
mod tests {
  use card::keyword::Keyword::*;

  const LINES: [&'static str; 20] = [
    /* 0 */
    "NODE  /        1              0.             0.5              0.",
    /* 1 */
    "NODE  /        1              0.             0.5              0.",
    /* 2 */
    "NODE  /        1              0.             0.5              0.",
    /* 3 */
    "NODE  /        1              0.             0.5              0.",
    /* 4 */
    "#Comment here",
    /* 5 */
    "SHELL /     3129       1       1    2967    2971    2970",
    /* 6 */
    "invalid line here",
    /* 7 */
    "SHELL /     3129       1       1    2967    2971    2970",
    /* 8 */
    "SHELL /     3129       1       1    2967    2971    2970",
    /* 9 */
    "#Comment",
    /* 10 */
    "#Comment",
    /* 11 */
    "SHELL /     3129       1       1    2967    2971    2970",
    /* 12 */
    "SHELL /     3129       1       1    2967    2971    2970",
    /* 13 */
    "$Comment",
    /* 14 */
    "SHELL /     3129       1       1    2967    2971    2970",
    /* 15 */
    "SHELL /     3129       1       1    2967    2971    2970",
    /* 16 */
    "$Comment",
    /* 17 */
    "#Comment",
    /* 18 */
    "NODE  /        1              0.             0.5              0.",
    /* 19 */
    "NODE  /        1              0.             0.5              0.",
  ];

  cardtest!(
    fold_general1,
    LINES,
    vec![(0, 3, Node), (5, 5, Shell), (7, 15, Shell), (18, 19, Node)]
  );

  cardtest!(
    fold_general2,
    LINES[4..],
    vec![(1, 1, Shell), (3, 11, Shell), (14, 15, Node)]
  );

  cardtest!(
    fold_general3,
    LINES[6..],
    vec![(1, 9, Shell), (12, 13, Node)]
  );

  cardtest!(
    fold_general4,
    LINES[13..19],
    vec![(1, 2, Shell), (5, 5, Node)]
  );

  const LINES2: [&'static str; 24] = [
    // 0
    "NODE  /        1              0.             0.5              0.",
    // 1
    "NODE  /        1              0.             0.5              0.",
    // 2
    "NODE  /        1              0.             0.5              0.",
    // 3
    "NODE  /        1              0.             0.5              0.",
    // 4
    "#Comment here",
    // 5
    "SHELL /     3129       1       1    2967    2971    2970",
    // 6
    "NODE  /     3129       1       1    2967    2971    2970",
    // 7
    "NODE  /     3129       1       1    2967    2971    2970",
    // 8
    "#Comment",
    // 9
    "#Comment",
    // 10
    "SHELL /     3129       1       1    2967    2971    2970",
    // 11
    "SHELL /     3129       1       1    2967    2971    2970",
    // 12
    "$Comment",
    // 13
    "SHELL /     3129       1       1    2967    2971    2970",
    // 14
    "SHELL /     3129       1       1    2967    2971    2970",
    // 15
    "$Comment",
    // 16
    "#Comment",
    // 17
    "NODE  /        1              0.             0.5              0.",
    // 18
    "NODE  /        1              0.             0.5              0.",
    // 19
    "NODE  /        1              0.             0.5              0.",
    // 20
    "SHELL /     3129       1       1    2967    2971    2970",
    // 21
    "SHELL /     3129       1       1    2967    2971    2970",
    // 22
    "SHELL /     3129       1       1    2967    2971    2970",
    // 23
    "SHELL /     3129       1       1    2967    2971    2970",
  ];

  cardtest!(
    fold_general_gather,
    LINES2,
    vec![
      (0, 3, Node),
      (5, 5, Shell),
      (6, 7, Node),
      (10, 14, Shell),
      (17, 19, Node),
      (20, 23, Shell),
    ]
  );

  const RBODIES: [&'static str; 13] = [
    "RBODY /        1               0       0                       0       0        ",
    "NAME RBODY / ->1                                                                ",
    "        END",
    "RBODY /        1               0       0                       0       0        ",
    "NAME RBODY / ->1                                                                ",
    "        END",
    "RBODY /        1               0       0                       0       0        ",
    "#COMMENT",
    "NAME RBODY / ->1                                                                ",
    "        END",
    "RBODY /        1               0       0                       0       0        ",
    "NAME RBODY / ->1                                                                ",
    "        END",
  ];

  cardtest!(
    fold_level2_rbodies,
    RBODIES,
    vec![
      (0, 2, Rbody0),
      (3, 5, Rbody0),
      (6, 9, Rbody0),
      (10, 12, Rbody0),
    ],
    vec![(0, 12, Rbody0)]
  );

}