use crate::dir::Dir;
use crate::types::{Epoch, Rank};

use anyhow::{anyhow, bail, Context, Result};
use indoc::indoc;
use std::fs::{self, File};
use std::io::{self, BufRead, BufReader, BufWriter};
use std::path::{Path, PathBuf};

pub struct DB {
    path: PathBuf,
    dirs: Vec<Dir>,
    modified: bool,
}

impl DB {
    pub fn open<P: AsRef<Path>>(path: P) -> Result<DB> {
        let path = path.as_ref().to_path_buf();

        let dirs = match File::open(&path) {
            Ok(file) => {
                let reader = BufReader::new(&file);
                bincode::config()
                    .limit(8 * 1024 * 1024) // only databases upto 8 MiB are supported
                    .deserialize_from(reader)
                    .context("could not deserialize database")?
            }
            Err(err) => match err.kind() {
                io::ErrorKind::NotFound => Vec::<Dir>::new(),
                _ => return Err(err).context("could not open database file"),
            },
        };

        Ok(DB {
            path,
            dirs,
            modified: false,
        })
    }

    pub fn save(&mut self) -> Result<()> {
        if self.modified {
            let path_tmp = self.get_path_tmp();

            let file_tmp =
                File::create(&path_tmp).context("could not open temporary database file")?;

            let writer = BufWriter::new(&file_tmp);
            bincode::serialize_into(writer, &self.dirs).context("could not serialize database")?;

            fs::rename(&path_tmp, &self.path).context("could not move temporary database file")?;
        }

        Ok(())
    }

    pub fn migrate<P: AsRef<Path>>(&mut self, path: P, merge: bool) -> Result<()> {
        if !self.dirs.is_empty() && !merge {
            bail!(indoc!(
                "To prevent conflicts, you can only migrate from z with an empty zoxide database!
                If you wish to merge the two, specify the `--merge` flag."
            ));
        }

        let z_db_file = File::open(path).context("could not open z database file")?;
        let reader = BufReader::new(z_db_file);

        for (idx, read_line) in reader.lines().enumerate() {
            let line_number = idx + 1;
            let line = if let Ok(line) = read_line {
                line
            } else {
                eprintln!(
                    "could not read entry at line {}: {:?}",
                    line_number, read_line
                );
                continue;
            };

            let split_line = line.rsplitn(3, '|').collect::<Vec<&str>>();

            match split_line.as_slice() {
                [epoch_str, rank_str, path_str] => {
                    let epoch = match epoch_str.parse::<i64>() {
                        Ok(epoch) => epoch,
                        Err(e) => {
                            eprintln!(
                                "invalid epoch '{}' at line {}: {}",
                                epoch_str, line_number, e
                            );
                            continue;
                        }
                    };
                    let rank = match rank_str.parse::<f64>() {
                        Ok(rank) => rank,
                        Err(e) => {
                            eprintln!("invalid rank '{}' at line {}: {}", rank_str, line_number, e);
                            continue;
                        }
                    };
                    let path_abs = match Path::new(path_str).canonicalize() {
                        Ok(path) => path,
                        Err(e) => {
                            eprintln!("invalid path '{}' at line {}: {}", path_str, line_number, e);
                            continue;
                        }
                    };

                    if merge {
                        // If the path exists in the database, add the ranks and set the epoch to
                        // the largest of the parsed epoch and the already present epoch.
                        if let Some(dir) = self.dirs.iter_mut().find(|dir| dir.path == path_abs) {
                            dir.rank += rank;
                            dir.last_accessed = Epoch::max(epoch, dir.last_accessed);

                            continue;
                        };
                    }

                    // FIXME: When we switch to PathBuf for storing directories inside Dir, just
                    // pass `PathBuf::from(path_str)`
                    self.dirs.push(Dir {
                        path: path_abs,
                        rank,
                        last_accessed: epoch,
                    });
                }
                [] | [""] => {} // ignore blank lines
                line => {
                    eprintln!("invalid entry at line {}: {:?}", line_number, line);
                    continue;
                }
            };
        }

        self.modified = true;

        Ok(())
    }

    pub fn add<P: AsRef<Path>>(&mut self, path: P, max_age: Rank, now: Epoch) -> Result<()> {
        let path_abs = path
            .as_ref()
            .canonicalize()
            .with_context(|| anyhow!("could not access directory: {}", path.as_ref().display()))?;

        match self.dirs.iter_mut().find(|dir| dir.path == path_abs) {
            None => self.dirs.push(Dir {
                path: path_abs,
                last_accessed: now,
                rank: 1.0,
            }),
            Some(dir) => {
                dir.last_accessed = now;
                dir.rank += 1.0;
            }
        };

        let sum_age = self.dirs.iter().map(|dir| dir.rank).sum::<Rank>();

        if sum_age > max_age {
            let factor = 0.9 * max_age / sum_age;
            for dir in &mut self.dirs {
                dir.rank *= factor;
            }
        }

        self.dirs.retain(|dir| dir.rank >= 1.0);
        self.modified = true;

        Ok(())
    }

    pub fn query(&mut self, keywords: &[String], now: Epoch) -> Option<Dir> {
        let (idx, dir) = self
            .dirs
            .iter()
            .enumerate()
            .filter(|(_, dir)| dir.is_match(&keywords))
            .max_by_key(|(_, dir)| dir.get_frecency(now) as i64)?;

        if dir.is_dir() {
            Some(dir.to_owned())
        } else {
            self.dirs.swap_remove(idx);
            self.modified = true;
            self.query(keywords, now)
        }
    }

    pub fn query_all(&mut self, keywords: &[String]) -> Vec<Dir> {
        self.remove_invalid();

        self.dirs
            .iter()
            .filter(|dir| dir.is_match(&keywords))
            .cloned()
            .collect()
    }

    pub fn remove<P: AsRef<Path>>(&mut self, path: P) -> Result<()> {
        let path_abs = match path.as_ref().canonicalize() {
            Ok(path_abs) => path_abs,
            Err(_) => path.as_ref().to_path_buf(),
        };

        if let Some(idx) = self.dirs.iter().position(|dir| dir.path == path_abs) {
            self.dirs.swap_remove(idx);
            self.modified = true;
        }

        Ok(())
    }

    fn get_path_tmp(&self) -> PathBuf {
        let mut path_tmp = self.path.clone();
        path_tmp.set_file_name(".zo.tmp");
        path_tmp
    }

    fn remove_invalid(&mut self) {
        let orig_len = self.dirs.len();
        self.dirs.retain(Dir::is_dir);

        if orig_len != self.dirs.len() {
            self.modified = true;
        }
    }
}

impl Drop for DB {
    fn drop(&mut self) {
        if let Err(e) = self.save() {
            eprintln!("{:#}", e);
        }
    }
}