use std::fmt::Write;
use std::{fmt::Display, path::PathBuf, process::Child};

use anyhow::{Result, anyhow, bail};

use crate::cmd::zfs::*;

/// A ZFS pool. It holds the name of the pool and the list of datasets belonging to it.
pub struct ZPool {
    pub name: String,
    pub datasets: Vec<Dataset>,
}

impl ZPool {
    pub fn new(arg: &str) -> Result<Self> {
        let result = Self {
            name: arg.to_string(),
            datasets: Vec::new(),
        };

        if !result.exists() {
            bail!("pool does not exist")
        }
        Ok(result)
    }

    fn exists(&self) -> bool {
        pool_exists(&self.name)
    }

    pub fn send_absolute(&self, dataset_to_send: &Dataset, snapshot: &Snapshot) -> Result<Child> {
        assert!(self.datasets.contains(dataset_to_send));

        let mut qualified_name = dataset_to_send.0.to_str().unwrap().to_string();
        qualified_name.push('@');
        qualified_name.push_str(&snapshot.0);

        let handle = zfs_send_absolute(&qualified_name)?;
        Ok(handle)
    }

    pub fn send_incremental(
        &self,
        dataset_to_send: &Dataset,
        common_snapshot: &Snapshot,
        recent_snapshot: &Snapshot,
    ) -> Result<Child> {
        let mut from = String::new();
        let mut to = String::new();
        write!(from, "@{common_snapshot}")?;
        write!(to, "{dataset_to_send}@{recent_snapshot}")?;
        zfs_send_incremental(&from, &to)
    }

    pub fn receive(&self, handle: Child) -> Result<()> {
        zfs_receive(&self.name, handle)?;
        Ok(())
    }

    pub fn get_datasets_from_system(&mut self) -> Result<()> {
        let datasets = zfs_list_main_datasets(&self.name)?;

        self.datasets = datasets
            .iter()
            .map(PathBuf::from)
            .map(Dataset::new)
            .skip(1)
            .collect(); // first one is the Pool

        Ok(())
    }

    pub fn contains(&self, dataset: &Dataset) -> bool {
        self.datasets.contains(dataset)
    }

    pub fn get_matching_dataset(&self, dataset_from_other_pool: &Dataset) -> Option<Dataset> {
        let mut required_name = PathBuf::new();
        required_name.push(&self.name);
        dataset_from_other_pool
            .0
            .iter()
            .skip(1)
            .for_each(|element| required_name.push(element));
        let matching_dataset = Dataset::new(required_name);
        if self.contains(&matching_dataset) {
            Some(matching_dataset)
        } else {
            None
        }
    }

    pub fn export(self) -> Result<()> {
        zpool_export(&self.name)
    }

    pub fn scrub(&self) -> Result<()> {
        zpool_scrub(&self.name)
    }

    pub fn import(name: &str) -> Result<ZPool> {
        zpool_import(name)?;
        let result = ZPool::new(name)?;
        Ok(result)
    }
}

/// Full path of a ZFS dataset.
///
/// E.g. if the name of the pool is `tank`, with the elements `ROOT` and `default` below it, this
/// struct would contain `tank/ROOT/default`.
#[derive(Debug, PartialEq, Clone)]
pub struct Dataset(PathBuf);

impl Dataset {
    fn new(path: PathBuf) -> Self {
        Self(path)
    }

    pub fn find_snapshots_like_tag(
        &self,
        snapshot_tag: &str,
        snapshot_interval: &str,
    ) -> Result<Vec<Snapshot>> {
        let snapshots = zfs_list_snapshots(self.0.to_str().unwrap())?;

        let mut result = vec![];

        for item in snapshots {
            let snapshot_name = item.split('@').next_back().unwrap();
            if snapshot_name.contains(snapshot_tag) && snapshot_name.contains(snapshot_interval) {
                result.push(Snapshot(snapshot_name.to_string()));
            }
        }

        Ok(result)
    }

    pub fn find_last_snapshot_with_tag(
        &self,
        snapshot_tag: &str,
        snapshot_interval: &str,
    ) -> Result<Snapshot> {
        let mut snapshots = self.find_snapshots_like_tag(snapshot_tag, snapshot_interval)?;
        snapshots.sort_unstable();
        let result = snapshots
            .last()
            .cloned()
            .ok_or(anyhow!("could not find any snapshots"))?;
        Ok(result)
    }

    fn get_snapshots(&self) -> Result<Vec<Snapshot>> {
        let snapshots_string = zfs_list_snapshots(self.0.to_str().unwrap())?;
        let snapshots = snapshots_string
            .into_iter()
            // TODO should snapshot just take a string?
            .map(|s| Snapshot::new(&s))
            .collect();
        Ok(snapshots)
    }

    pub fn change_pool_name(&self, new_pool: &ZPool) -> Self {
        let new_pool = new_pool.name.as_str();
        let mut pathbuf = PathBuf::new();
        pathbuf.push(new_pool);
        self.0
            .iter()
            .skip(1)
            .for_each(|element| pathbuf.push(element));

        Self(pathbuf)
    }
}

impl Display for Dataset {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0.to_str().unwrap())
    }
}

#[derive(Debug, Clone, PartialEq, PartialOrd, Ord, Eq)]
/// A ZFS snapshot.
///
/// If the absolute ZFS path were "zpool/dataset@snapshot", this would contain "snapshot".
pub struct Snapshot(String);

impl Snapshot {
    fn new(name: &str) -> Self {
        Self(name.to_string())
    }

    pub fn find_last_common_snapshot_with_tag(
        ds1: &Dataset,
        ds2: &Dataset,
        tag: &str,
    ) -> Option<Self> {
        let sn1 = ds1.get_snapshots().ok()?;
        let sn2 = ds2.get_snapshots().ok()?;
        let mut common = vec![];

        for snapshot in sn1 {
            if !snapshot.0.contains(tag) {
                continue;
            }
            if sn2.contains(&snapshot) {
                common.push(snapshot);
            }
        }

        common.sort();
        common.last().cloned()
    }
}

impl Display for Snapshot {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.0)
    }
}