//! Upload, download, delete and synchronise project files with a deployment
//! server over SFTP.

use crate::mapping::{Excludes, Mappings, posix};
use ide_core::{CancellationToken, IdeError, IdeResult};
use ide_ssh::RemoteFs;
use ide_ssh::sftp::mtime_of;
use serde::{Deserialize, Serialize};
use specta::Type;
use std::collections::BTreeMap;
use std::path::{Path, PathBuf};

/// Modification times closer than this count as equal (FAT, rounding by servers).
const MTIME_SLACK: u32 = 2;

#[derive(Debug, Clone, Default, PartialEq, Eq, Serialize, Deserialize, Type)]
#[serde(rename_all = "camelCase")]
pub struct TransferReport {
    pub files: u32,
    /// Files left alone: excluded, or outside every mapping.
    pub skipped: u32,
    pub errors: Vec<TransferError>,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, Type)]
#[serde(rename_all = "camelCase")]
pub struct TransferError {
    pub path: String,
    pub message: String,
}

impl TransferReport {
    fn fail(&mut self, path: impl Into<String>, e: IdeError) {
        self.errors.push(TransferError { path: path.into(), message: e.message });
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Type)]
#[serde(rename_all = "camelCase")]
pub struct FileStamp {
    pub size: u64,
    pub mtime: Option<u32>,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Type)]
#[serde(rename_all = "camelCase")]
pub enum SyncStatus {
    LocalOnly,
    RemoteOnly,
    LocalNewer,
    RemoteNewer,
    /// Same time, different size.
    Different,
    Same,
}

/// One file of Sync with Deployed.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, Type)]
#[serde(rename_all = "camelCase")]
pub struct SyncEntry {
    /// Project-relative, `/`-separated.
    pub path: String,
    pub remote_path: String,
    pub local: Option<FileStamp>,
    pub remote: Option<FileStamp>,
    pub status: SyncStatus,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Type)]
#[serde(rename_all = "camelCase")]
pub enum SyncAction {
    Upload,
    Download,
    DeleteRemote,
    DeleteLocal,
}

#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, Type)]
#[serde(rename_all = "camelCase")]
pub struct SyncStep {
    /// Project-relative, `/`-separated.
    pub path: String,
    pub action: SyncAction,
}

pub fn status(local: Option<FileStamp>, remote: Option<FileStamp>) -> SyncStatus {
    match (local, remote) {
        (Some(_), None) => SyncStatus::LocalOnly,
        (None, Some(_)) | (None, None) => SyncStatus::RemoteOnly,
        (Some(l), Some(r)) => match (l.mtime, r.mtime) {
            (Some(lt), Some(rt)) if lt > rt + MTIME_SLACK => SyncStatus::LocalNewer,
            (Some(lt), Some(rt)) if rt > lt + MTIME_SLACK => SyncStatus::RemoteNewer,
            _ if l.size != r.size => SyncStatus::Different,
            _ => SyncStatus::Same,
        },
    }
}

/// Operations on one server through one SFTP session.
pub struct Deployment<'a> {
    pub fs: &'a RemoteFs,
    pub map: &'a Mappings,
    pub exclude: &'a Excludes,
    pub preserve_time: bool,
    pub cancel: CancellationToken,
}

impl Deployment<'_> {
    fn rel(&self, local: &Path) -> String {
        posix(local.strip_prefix(self.map.project_root()).unwrap_or(local))
    }

    fn excluded_local(&self, local: &Path) -> bool {
        self.exclude.local(local.strip_prefix(self.map.project_root()).unwrap_or(local))
    }

    /// Local files under `paths` (folders recursively), excluded names left out.
    fn local_files(&self, paths: &[PathBuf], report: &mut TransferReport) -> Vec<PathBuf> {
        let mut out = Vec::new();
        for p in paths {
            if self.excluded_local(p) {
                report.skipped += 1;
                continue;
            }
            if p.is_dir() {
                let walk = ignore::WalkBuilder::new(p).standard_filters(false).follow_links(false).build();
                for entry in walk.flatten() {
                    let path = entry.path();
                    if entry.file_type().is_some_and(|t| t.is_file()) {
                        if self.excluded_local(path) {
                            report.skipped += 1;
                        } else {
                            out.push(path.to_path_buf());
                        }
                    }
                }
            } else if p.is_file() {
                out.push(p.clone());
            }
        }
        out
    }

    /// Remote files under `dir` (recursively), excluded ones left out.
    async fn remote_files(&self, dir: &str, out: &mut Vec<ide_ssh::RemoteEntry>) -> IdeResult<()> {
        for e in self.fs.list(dir).await? {
            if self.cancel.is_cancelled() {
                return Err(IdeError::cancelled());
            }
            if self.exclude.remote(&e.path) {
                continue;
            }
            if e.is_dir && !e.is_symlink {
                Box::pin(self.remote_files(&e.path, out)).await?;
            } else if !e.is_dir {
                out.push(e);
            }
        }
        Ok(())
    }

    pub async fn upload(
        &self,
        paths: &[PathBuf],
        progress: &mut (dyn FnMut(&str, usize, usize) + Send),
    ) -> TransferReport {
        let mut report = TransferReport::default();
        let files = self.local_files(paths, &mut report);
        for (i, local) in files.iter().enumerate() {
            if self.cancel.is_cancelled() {
                break;
            }
            let rel = self.rel(local);
            let Some(remote) = self.map.remote(local).filter(|r| !self.exclude.remote(r)) else {
                report.skipped += 1;
                continue;
            };
            progress(&rel, i, files.len());
            match self.fs.upload(local, &remote, self.preserve_time).await {
                Ok(()) => report.files += 1,
                Err(e) => report.fail(rel, e),
            }
        }
        report
    }

    /// Downloads the remote counterparts of `paths` (folders recursively).
    pub async fn download(
        &self,
        paths: &[PathBuf],
        progress: &mut (dyn FnMut(&str, usize, usize) + Send),
    ) -> TransferReport {
        let mut report = TransferReport::default();
        let mut jobs: Vec<(String, PathBuf)> = Vec::new();
        for p in paths {
            let Some(remote) = self.map.remote(p).filter(|r| !self.exclude.remote(r)) else {
                report.skipped += 1;
                continue;
            };
            match self.fs.stat(&remote).await {
                Ok(Some(e)) if e.is_dir => {
                    let mut files = Vec::new();
                    if let Err(e) = self.remote_files(&remote, &mut files).await {
                        report.fail(self.rel(p), e);
                    }
                    for f in files {
                        if let Some(local) = self.map.local(&f.path) {
                            jobs.push((f.path, local));
                        }
                    }
                }
                Ok(Some(_)) => jobs.push((remote, p.clone())),
                Ok(None) => {
                    report.fail(self.rel(p), IdeError::not_found(format!("{remote} does not exist on the server")))
                }
                Err(e) => report.fail(self.rel(p), e),
            }
        }
        for (i, (remote, local)) in jobs.iter().enumerate() {
            if self.cancel.is_cancelled() {
                break;
            }
            if self.excluded_local(local) {
                report.skipped += 1;
                continue;
            }
            let rel = self.rel(local);
            progress(&rel, i, jobs.len());
            match self.fs.download(remote, local).await {
                Ok(()) => report.files += 1,
                Err(e) => report.fail(rel, e),
            }
        }
        report
    }

    /// Deletes the remote counterparts of `paths`.
    pub async fn delete_remote(&self, paths: &[PathBuf]) -> TransferReport {
        let mut report = TransferReport::default();
        for p in paths {
            // Never a whole mapping (the project folder went away, or a mapped folder did).
            let Some(remote) = self.map.remote(p).filter(|r| !self.exclude.remote(r) && !self.map.is_root(r)) else {
                report.skipped += 1;
                continue;
            };
            match self.fs.stat(&remote).await {
                Ok(None) => {}
                Ok(Some(_)) => match self.fs.remove(&remote).await {
                    Ok(()) => report.files += 1,
                    Err(e) => report.fail(self.rel(p), e),
                },
                Err(e) => report.fail(self.rel(p), e),
            }
        }
        report
    }

    /// Sync with Deployed: local and remote files under `local` side by side.
    pub async fn compare(&self, local: &Path) -> IdeResult<Vec<SyncEntry>> {
        let remote_root =
            self.map.remote(local).ok_or_else(|| IdeError::invalid(format!("{} is not mapped", local.display())))?;
        let mut by_rel: BTreeMap<String, SyncEntry> = BTreeMap::new();
        let mut ignored = TransferReport::default();
        for f in self.local_files(&[local.to_path_buf()], &mut ignored) {
            let Some(remote_path) = self.map.remote(&f) else { continue };
            let size = std::fs::metadata(&f).map(|m| m.len()).unwrap_or(0);
            let stamp = FileStamp { size, mtime: mtime_of(&f) };
            by_rel.insert(
                self.rel(&f),
                SyncEntry {
                    path: self.rel(&f),
                    remote_path,
                    local: Some(stamp),
                    remote: None,
                    status: SyncStatus::LocalOnly,
                },
            );
        }
        let mut remote = Vec::new();
        match self.fs.stat(&remote_root).await? {
            Some(e) if e.is_dir => self.remote_files(&remote_root, &mut remote).await?,
            Some(e) => remote.push(e),
            None => {}
        }
        for e in remote {
            let Some(l) = self.map.local(&e.path) else { continue };
            if self.excluded_local(&l) {
                continue;
            }
            let rel = self.rel(&l);
            let stamp = FileStamp { size: e.size, mtime: e.mtime };
            by_rel.entry(rel.clone()).and_modify(|x| x.remote = Some(stamp)).or_insert(SyncEntry {
                path: rel,
                remote_path: e.path,
                local: None,
                remote: Some(stamp),
                status: SyncStatus::RemoteOnly,
            });
        }
        Ok(by_rel
            .into_values()
            .map(|mut e| {
                e.status = status(e.local, e.remote);
                e
            })
            .collect())
    }

    /// Applies the chosen Sync with Deployed actions.
    pub async fn apply(
        &self,
        steps: &[SyncStep],
        progress: &mut (dyn FnMut(&str, usize, usize) + Send),
    ) -> TransferReport {
        let mut report = TransferReport::default();
        let root = self.map.project_root().to_path_buf();
        for (i, step) in steps.iter().enumerate() {
            if self.cancel.is_cancelled() {
                break;
            }
            let local = step.path.split('/').filter(|s| !s.is_empty()).fold(root.clone(), |p, s| p.join(s));
            let Some(remote) =
                self.map.remote(&local).filter(|r| !self.exclude.remote(r) && !self.excluded_local(&local))
            else {
                report.skipped += 1;
                continue;
            };
            progress(&step.path, i, steps.len());
            let r = match step.action {
                SyncAction::Upload => self.fs.upload(&local, &remote, self.preserve_time).await,
                SyncAction::Download => self.fs.download(&remote, &local).await,
                SyncAction::DeleteRemote => self.fs.remove(&remote).await,
                SyncAction::DeleteLocal => std::fs::remove_file(&local).map_err(IdeError::from),
            };
            match r {
                Ok(()) => report.files += 1,
                Err(e) => report.fail(step.path.clone(), e),
            }
        }
        report
    }

    /// Uploads what changed locally under `local` (new, newer or resized files): sync before a run.
    pub async fn push_changes(
        &self,
        local: &Path,
        progress: &mut (dyn FnMut(&str, usize, usize) + Send),
    ) -> IdeResult<TransferReport> {
        let steps: Vec<SyncStep> = self
            .compare(local)
            .await?
            .into_iter()
            .filter(|e| matches!(e.status, SyncStatus::LocalOnly | SyncStatus::LocalNewer | SyncStatus::Different))
            .map(|e| SyncStep { path: e.path, action: SyncAction::Upload })
            .collect();
        Ok(self.apply(&steps, progress).await)
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    fn stamp(size: u64, mtime: u32) -> Option<FileStamp> {
        Some(FileStamp { size, mtime: Some(mtime) })
    }

    #[test]
    fn compares_by_time_then_size() {
        assert_eq!(status(stamp(1, 100), None), SyncStatus::LocalOnly);
        assert_eq!(status(None, stamp(1, 100)), SyncStatus::RemoteOnly);
        assert_eq!(status(stamp(1, 200), stamp(1, 100)), SyncStatus::LocalNewer);
        assert_eq!(status(stamp(1, 100), stamp(1, 200)), SyncStatus::RemoteNewer);
        assert_eq!(status(stamp(1, 101), stamp(1, 100)), SyncStatus::Same);
        assert_eq!(status(stamp(2, 100), stamp(1, 100)), SyncStatus::Different);
    }
}