use crate::tools;

use failure::*;
use regex::Regex;
use std::os::unix::io::RawFd;
use std::collections::{HashMap, HashSet};

use chrono::{DateTime, Datelike, TimeZone, SecondsFormat, Utc, Local};

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

macro_rules! BACKUP_ID_RE { () => (r"[A-Za-z0-9][A-Za-z0-9_-]+") }
macro_rules! BACKUP_TYPE_RE { () => (r"(?:host|vm|ct)") }
macro_rules! BACKUP_TIME_RE { () => (r"[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}Z") }

lazy_static!{
    static ref BACKUP_FILE_REGEX: Regex = Regex::new(
        r"^.*\.([fd]idx|blob)$").unwrap();

    static ref BACKUP_TYPE_REGEX: Regex = Regex::new(
        concat!(r"^(", BACKUP_TYPE_RE!(), r")$")).unwrap();

    static ref BACKUP_ID_REGEX: Regex = Regex::new(
        concat!(r"^", BACKUP_ID_RE!(), r"$")).unwrap();

    static ref BACKUP_DATE_REGEX: Regex = Regex::new(
        concat!(r"^", BACKUP_TIME_RE!() ,r"$")).unwrap();

    static ref GROUP_PATH_REGEX: Regex = Regex::new(
        concat!(r"(", BACKUP_TYPE_RE!(), ")/(", BACKUP_ID_RE!(), r")$")).unwrap();

    static ref SNAPSHOT_PATH_REGEX: Regex = Regex::new(
        concat!(r"(", BACKUP_TYPE_RE!(), ")/(", BACKUP_ID_RE!(), ")/(", BACKUP_TIME_RE!(), r")$")).unwrap();

}

/// BackupGroup is a directory containing a list of BackupDir
#[derive(Debug, Clone)]
pub struct BackupGroup {
    /// Type of backup
    backup_type: String,
    /// Unique (for this type) ID
    backup_id: String,
}

enum PruneMark { Keep, Remove }

impl BackupGroup {

    pub fn new<T: Into<String>, U: Into<String>>(backup_type: T, backup_id: U) -> Self {
        Self { backup_type: backup_type.into(), backup_id: backup_id.into() }
    }

    pub fn backup_type(&self) -> &str {
        &self.backup_type
    }

    pub fn backup_id(&self) -> &str {
        &self.backup_id
    }

    pub fn parse(path: &str) -> Result<Self, Error> {

        let cap = GROUP_PATH_REGEX.captures(path)
            .ok_or_else(|| format_err!("unable to parse backup group path '{}'", path))?;

        Ok(Self {
            backup_type: cap.get(1).unwrap().as_str().to_owned(),
            backup_id: cap.get(2).unwrap().as_str().to_owned(),
        })
    }

    pub fn group_path(&self) ->  PathBuf  {

        let mut relative_path = PathBuf::new();

        relative_path.push(&self.backup_type);

        relative_path.push(&self.backup_id);

        relative_path
    }

    pub fn list_backups(&self, base_path: &Path) -> Result<Vec<BackupInfo>, Error> {

        let mut list = vec![];

        let mut path = base_path.to_owned();
        path.push(self.group_path());

        tools::scandir(libc::AT_FDCWD, &path, &BACKUP_DATE_REGEX, |l2_fd, backup_time, file_type| {
            if file_type != nix::dir::Type::Directory { return Ok(()); }

            let dt = backup_time.parse::<DateTime<Utc>>()?;
            let backup_dir = BackupDir::new(self.backup_type.clone(), self.backup_id.clone(), dt.timestamp());
            let files = list_backup_files(l2_fd, backup_time)?;

            list.push(BackupInfo { backup_dir, files });

            Ok(())
        })?;
        Ok(list)
    }

    fn mark_selections<F: Fn(DateTime<Local>, &BackupInfo) -> String> (
        mark: &mut HashMap<PathBuf, PruneMark>,
        list: &Vec<BackupInfo>,
        keep: usize,
        select_id: F,
    ) {

        let mut hash = HashSet::new();
        for info in list {
            let backup_id = info.backup_dir.relative_path();
            if let Some(_) = mark.get(&backup_id) {
                continue;
            }
            let local_time = info.backup_dir.backup_time().with_timezone(&Local);
            let sel_id: String = select_id(local_time, &info);
            if !hash.contains(&sel_id) {
                if hash.len() >= keep { break; }
                hash.insert(sel_id);
                mark.insert(backup_id, PruneMark::Keep);
            } else {
                mark.insert(backup_id, PruneMark::Remove);
            }
        }
    }

    pub fn compute_prune_list(
        mut list: Vec<BackupInfo>,
        keep_last: Option<u64>,
        keep_daily: Option<u64>,
        keep_weekly: Option<u64>,
        keep_monthly: Option<u64>,
        keep_yearly: Option<u64>,
    ) -> Result<Vec<BackupInfo>, Error> {

        let mut mark = HashMap::new();
        
        BackupInfo::sort_list(&mut list, false);
        
        if let Some(keep_last) = keep_last {
            for _ in 0..keep_last {
                if list.is_empty() { break; }
                let info = list.remove(0);
                let backup_id = info.backup_dir.relative_path();
                mark.insert(backup_id, PruneMark::Keep);
            }
        }

        if let Some(keep_daily) = keep_daily {
            Self::mark_selections(&mut mark, &list, keep_daily as usize, |local_time, _info| {
                format!("{}/{}/{}", local_time.year(), local_time.month(), local_time.day())
            });
        }

        if let Some(keep_weekly) = keep_weekly {
            Self::mark_selections(&mut mark, &list, keep_weekly as usize, |local_time, _info| {
                format!("{}/{}", local_time.year(), local_time.iso_week().week())
            });
        }

        if let Some(keep_monthly) = keep_monthly {
            Self::mark_selections(&mut mark, &list, keep_monthly as usize, |local_time, _info| {
                format!("{}/{}", local_time.year(), local_time.month())
            });
        }

        if let Some(keep_yearly) = keep_yearly {
            Self::mark_selections(&mut mark, &list, keep_yearly as usize, |local_time, _info| {
                format!("{}/{}", local_time.year(), local_time.year())
            });
        }

        let mut remove_list: Vec<BackupInfo> = list.into_iter()
            .filter(|info| {
                let backup_id = info.backup_dir.relative_path();
                match mark.get(&backup_id) {
                    Some(PruneMark::Keep) => false,
                    _ => true,
                }
            })
            .collect();

        BackupInfo::sort_list(&mut remove_list, true);

        Ok(remove_list)
    }
}

/// Uniquely identify a Backup (relative to data store)
///
/// We also call this a backup snaphost.
#[derive(Debug, Clone)]
pub struct BackupDir {
    /// Backup group
    group: BackupGroup,
    /// Backup timestamp
    backup_time: DateTime<Utc>,
}

impl BackupDir {

    pub fn new<T, U>(backup_type: T, backup_id: U, timestamp: i64) -> Self
    where
        T: Into<String>,
        U: Into<String>,
    {
        // Note: makes sure that nanoseconds is 0
        Self {
            group: BackupGroup::new(backup_type.into(), backup_id.into()),
            backup_time: Utc.timestamp(timestamp, 0),
        }
    }
    pub fn new_with_group(group: BackupGroup, timestamp: i64) -> Self {
        Self { group, backup_time: Utc.timestamp(timestamp, 0) }
    }

    pub fn group(&self) -> &BackupGroup {
        &self.group
    }

    pub fn backup_time(&self) -> DateTime<Utc> {
        self.backup_time
    }

    pub fn parse(path: &str) -> Result<Self, Error> {

        let cap = SNAPSHOT_PATH_REGEX.captures(path)
            .ok_or_else(|| format_err!("unable to parse backup snapshot path '{}'", path))?;

        let group = BackupGroup::new(cap.get(1).unwrap().as_str(), cap.get(2).unwrap().as_str());
        let backup_time = cap.get(3).unwrap().as_str().parse::<DateTime<Utc>>()?;
        Ok(BackupDir::from((group, backup_time.timestamp())))
    }

    pub fn relative_path(&self) ->  PathBuf  {

        let mut relative_path = self.group.group_path();

        relative_path.push(Self::backup_time_to_string(self.backup_time));

        relative_path
    }

    pub fn backup_time_to_string(backup_time: DateTime<Utc>) -> String {
        backup_time.to_rfc3339_opts(SecondsFormat::Secs, true)
    }
}

impl From<(BackupGroup, i64)> for BackupDir {
    fn from((group, timestamp): (BackupGroup, i64)) -> Self {
        Self { group, backup_time: Utc.timestamp(timestamp, 0) }
    }
}

/// Detailed Backup Information, lists files inside a BackupDir
#[derive(Debug, Clone)]
pub struct BackupInfo {
    /// the backup directory
    pub backup_dir: BackupDir,
    /// List of data files
    pub files: Vec<String>,
}

impl BackupInfo {

    pub fn new(base_path: &Path, backup_dir: BackupDir) -> Result<BackupInfo, Error> {
        let mut path = base_path.to_owned();
        path.push(backup_dir.relative_path());

        let files = list_backup_files(libc::AT_FDCWD, &path)?;

        Ok(BackupInfo { backup_dir, files })
    }

    /// Finds the latest backup inside a backup group
    pub fn last_backup(base_path: &Path, group: &BackupGroup) -> Result<Option<BackupInfo>, Error> {
        let backups = group.list_backups(base_path)?;
        Ok(backups.into_iter().max_by_key(|item| item.backup_dir.backup_time()))
    }

    pub fn sort_list(list: &mut Vec<BackupInfo>, ascendending: bool) {
        if ascendending { // oldest first
            list.sort_unstable_by(|a, b| a.backup_dir.backup_time.cmp(&b.backup_dir.backup_time));
        } else { // newest first
            list.sort_unstable_by(|a, b| b.backup_dir.backup_time.cmp(&a.backup_dir.backup_time));
        }
    }

    pub fn list_files(base_path: &Path, backup_dir: &BackupDir) -> Result<Vec<String>, Error> {
        let mut path = base_path.to_owned();
        path.push(backup_dir.relative_path());

        let files = list_backup_files(libc::AT_FDCWD, &path)?;

        Ok(files)
    }

    pub fn list_backups(base_path: &Path) -> Result<Vec<BackupInfo>, Error> {
        let mut list = vec![];

        tools::scandir(libc::AT_FDCWD, base_path, &BACKUP_TYPE_REGEX, |l0_fd, backup_type, file_type| {
            if file_type != nix::dir::Type::Directory { return Ok(()); }
            tools::scandir(l0_fd, backup_type, &BACKUP_ID_REGEX, |l1_fd, backup_id, file_type| {
                if file_type != nix::dir::Type::Directory { return Ok(()); }
                tools::scandir(l1_fd, backup_id, &BACKUP_DATE_REGEX, |l2_fd, backup_time, file_type| {
                    if file_type != nix::dir::Type::Directory { return Ok(()); }

                    let dt = backup_time.parse::<DateTime<Utc>>()?;
                    let backup_dir = BackupDir::new(backup_type, backup_id, dt.timestamp());

                    let files = list_backup_files(l2_fd, backup_time)?;

                    list.push(BackupInfo { backup_dir, files });

                    Ok(())
                })
            })
        })?;
        Ok(list)
    }
}

fn list_backup_files<P: ?Sized + nix::NixPath>(dirfd: RawFd, path: &P) -> Result<Vec<String>, Error> {
    let mut files = vec![];

    tools::scandir(dirfd, path, &BACKUP_FILE_REGEX, |_, filename, file_type| {
        if file_type != nix::dir::Type::File { return Ok(()); }
        files.push(filename.to_owned());
        Ok(())
    })?;

    Ok(files)
}