doing-ops 0.2.4

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

use chrono::Local;
use doing_config::Config;
use doing_error::Result;
use doing_taskpaper::{Document, io as taskpaper_io};

/// Generate a backup prefix that uniquely identifies a source file by its canonical path.
///
/// Format: `{filename}_{path_hash}_` where `path_hash` is 16 hex characters derived from
/// hashing the full canonical path. This ensures files with the same name at different
/// locations get isolated backup histories.
pub fn backup_prefix(source: &Path) -> Result<String> {
  let stem = source.file_name().and_then(|n| n.to_str()).unwrap_or("unknown");
  let canonical = source.canonicalize().or_else(|_| {
    source
      .parent()
      .and_then(|p| p.canonicalize().ok())
      .map(|p| p.join(source.file_name().unwrap_or_default()))
      .ok_or_else(|| {
        std::io::Error::new(
          std::io::ErrorKind::NotFound,
          format!("cannot resolve canonical path for {}", source.display()),
        )
      })
  })?;

  let hash = fnv1a_hash(canonical.to_string_lossy().as_bytes());

  Ok(format!("{stem}_{hash:016x}_"))
}

/// Create a timestamped backup of `source` in `backup_dir`.
///
/// The backup filename follows the pattern `{stem}_{YYYYMMDD}_{HHMMSS}_{ffffff}.bak`.
/// Creates the backup directory if it does not exist.
pub fn create_backup(source: &Path, backup_dir: &Path) -> Result<PathBuf> {
  fs::create_dir_all(backup_dir)?;

  let prefix = backup_prefix(source)?;
  let timestamp = Local::now().format("%Y%m%d_%H%M%S_%6f");
  let backup_name = format!("{prefix}{timestamp}.bak");
  let backup_path = backup_dir.join(backup_name);

  fs::copy(source, &backup_path)?;
  Ok(backup_path)
}

/// List backups for `source` in `backup_dir`, sorted newest-first.
pub fn list_backups(source: &Path, backup_dir: &Path) -> Result<Vec<PathBuf>> {
  list_files_with_ext(source, backup_dir, ".bak")
}

/// List undone (consumed) backups for `source` in `backup_dir`, sorted newest-first.
pub fn list_undone(source: &Path, backup_dir: &Path) -> Result<Vec<PathBuf>> {
  list_files_with_ext(source, backup_dir, ".undone")
}

/// Remove old backups for `source` that exceed `history_size`.
///
/// Backups are identified by the `{stem}_*.bak` glob pattern in `backup_dir`
/// and sorted newest-first by filename (which embeds the timestamp).
/// The newest `history_size` backups are kept; the rest are deleted.
pub fn prune_backups(source: &Path, backup_dir: &Path, history_size: u32) -> Result<()> {
  let mut backups = list_backups(source, backup_dir)?;
  if backups.len() <= history_size as usize {
    return Ok(());
  }

  for old in backups.drain(history_size as usize..) {
    fs::remove_file(old)?;
  }

  Ok(())
}

/// Atomically write a `Document` to `path`, creating a backup first.
///
/// Steps:
/// 1. If the file already exists, create a timestamped backup.
/// 2. Prune old backups beyond `history_size`.
/// 3. Sort entries according to config, then write the document atomically.
pub fn write_with_backup(doc: &Document, path: &Path, config: &Config) -> Result<()> {
  if path.exists() {
    create_backup(path, &config.backup_dir)?;
    prune_backups(path, &config.backup_dir, config.history_size)?;
  }

  let mut doc = doc.clone();
  doc.sort_entries(config.doing_file_sort == doing_config::SortOrder::Desc);
  doc.dedup();
  taskpaper_io::write_file(&doc, path)
}

/// FNV-1a hash producing a stable 64-bit value regardless of Rust version.
fn fnv1a_hash(bytes: &[u8]) -> u64 {
  const FNV_OFFSET: u64 = 0xcbf29ce484222325;
  const FNV_PRIME: u64 = 0x00000100000001B3;

  let mut hash = FNV_OFFSET;
  for &byte in bytes {
    hash ^= byte as u64;
    hash = hash.wrapping_mul(FNV_PRIME);
  }
  hash
}

fn list_files_with_ext(source: &Path, backup_dir: &Path, ext: &str) -> Result<Vec<PathBuf>> {
  if !backup_dir.exists() {
    return Ok(Vec::new());
  }

  let prefix = backup_prefix(source)?;
  let mut backups: Vec<PathBuf> = fs::read_dir(backup_dir)?
    .collect::<std::result::Result<Vec<_>, _>>()?
    .into_iter()
    .map(|entry| entry.path())
    .filter(|path| {
      path
        .file_name()
        .and_then(|n| n.to_str())
        .map(|n| n.starts_with(&prefix) && n.ends_with(ext))
        .unwrap_or(false)
    })
    .collect();

  backups.sort_by(|a, b| b.cmp(a));
  Ok(backups)
}

#[cfg(test)]
mod test {
  use doing_config::SortOrder;
  use doing_taskpaper::{Entry, Note, Section, Tags};

  use super::*;

  fn sample_doc() -> Document {
    let mut doc = Document::new();
    let mut section = Section::new("Currently");
    section.add_entry(Entry::new(
      chrono::Local::now(),
      "Test task",
      Tags::new(),
      Note::new(),
      "Currently",
      None::<String>,
    ));
    doc.add_section(section);
    doc
  }

  mod backup_prefix {
    use pretty_assertions::assert_eq;

    use super::*;

    #[test]
    fn it_produces_deterministic_hash() {
      let dir = tempfile::tempdir().unwrap();
      let source = dir.path().join("test.md");
      fs::write(&source, "").unwrap();

      let prefix1 = backup_prefix(&source).unwrap();
      let prefix2 = backup_prefix(&source).unwrap();

      assert_eq!(prefix1, prefix2);
    }
  }

  mod fnv1a_hash {
    use pretty_assertions::assert_eq;

    use super::super::fnv1a_hash;

    #[test]
    fn it_produces_known_output_for_known_input() {
      // FNV-1a of "hello" is a well-known value
      let hash = fnv1a_hash(b"hello");

      assert_eq!(hash, 0xa430d84680aabd0b);
    }
  }

  mod create_backup {
    use pretty_assertions::assert_eq;

    use super::*;

    #[test]
    fn it_copies_file_to_backup_dir() {
      let dir = tempfile::tempdir().unwrap();
      let source = dir.path().join("test.md");
      let backup_dir = dir.path().join("backups");
      fs::write(&source, "content").unwrap();

      let backup = create_backup(&source, &backup_dir).unwrap();

      assert!(backup.exists());
      assert_eq!(fs::read_to_string(&backup).unwrap(), "content");
    }

    #[test]
    fn it_creates_backup_dir_if_missing() {
      let dir = tempfile::tempdir().unwrap();
      let source = dir.path().join("test.md");
      let backup_dir = dir.path().join("nested/backups");
      fs::write(&source, "content").unwrap();

      create_backup(&source, &backup_dir).unwrap();

      assert!(backup_dir.exists());
    }

    #[test]
    fn it_uses_timestamped_bak_filename() {
      let dir = tempfile::tempdir().unwrap();
      let source = dir.path().join("doing.md");
      let backup_dir = dir.path().join("backups");
      fs::write(&source, "content").unwrap();

      let backup = create_backup(&source, &backup_dir).unwrap();
      let name = backup.file_name().unwrap().to_str().unwrap();
      let prefix = backup_prefix(&source).unwrap();

      assert!(name.starts_with(&prefix));
      assert!(name.ends_with(".bak"));
    }
  }

  mod list_backups {
    use pretty_assertions::assert_eq;

    use super::*;

    #[test]
    fn it_isolates_backups_by_source_path() {
      let dir = tempfile::tempdir().unwrap();
      let backup_dir = dir.path().join("backups");
      fs::create_dir_all(&backup_dir).unwrap();

      let dir_a = dir.path().join("a");
      let dir_b = dir.path().join("b");
      fs::create_dir_all(&dir_a).unwrap();
      fs::create_dir_all(&dir_b).unwrap();

      let source_a = dir_a.join("doing.md");
      let source_b = dir_b.join("doing.md");
      fs::write(&source_a, "content a").unwrap();
      fs::write(&source_b, "content b").unwrap();

      create_backup(&source_a, &backup_dir).unwrap();
      create_backup(&source_b, &backup_dir).unwrap();

      let backups_a = list_backups(&source_a, &backup_dir).unwrap();
      let backups_b = list_backups(&source_b, &backup_dir).unwrap();

      assert_eq!(backups_a.len(), 1);
      assert_eq!(backups_b.len(), 1);
      assert_eq!(fs::read_to_string(&backups_a[0]).unwrap(), "content a");
      assert_eq!(fs::read_to_string(&backups_b[0]).unwrap(), "content b");
    }
  }

  mod prune_backups {
    use super::*;

    #[test]
    fn it_does_nothing_when_under_limit() {
      let dir = tempfile::tempdir().unwrap();
      let source = dir.path().join("test.md");
      let backup_dir = dir.path().join("backups");
      fs::create_dir_all(&backup_dir).unwrap();
      fs::write(&source, "").unwrap();

      let prefix = backup_prefix(&source).unwrap();
      fs::write(backup_dir.join(format!("{prefix}20240101_000001.bak")), "").unwrap();

      prune_backups(&source, &backup_dir, 5).unwrap();

      let remaining = list_backups(&source, &backup_dir).unwrap();
      assert_eq!(remaining.len(), 1);
    }

    #[test]
    fn it_keeps_only_history_size_newest_backups() {
      let dir = tempfile::tempdir().unwrap();
      let source = dir.path().join("test.md");
      let backup_dir = dir.path().join("backups");
      fs::create_dir_all(&backup_dir).unwrap();
      fs::write(&source, "").unwrap();

      let prefix = backup_prefix(&source).unwrap();
      for i in 1..=5 {
        let name = format!("{prefix}20240101_{:06}.bak", i);
        fs::write(backup_dir.join(name), "").unwrap();
      }

      prune_backups(&source, &backup_dir, 2).unwrap();

      let remaining = list_backups(&source, &backup_dir).unwrap();
      assert_eq!(remaining.len(), 2);
    }
  }

  mod write_with_backup {
    use pretty_assertions::assert_eq;

    use super::*;

    #[test]
    fn it_creates_backup_before_writing() {
      let dir = tempfile::tempdir().unwrap();
      let path = dir.path().join("test.md");
      let backup_dir = dir.path().join("backups");
      fs::write(&path, "old content\n").unwrap();

      let mut config = Config::default();
      config.backup_dir = backup_dir.clone();
      config.doing_file_sort = SortOrder::Asc;

      write_with_backup(&sample_doc(), &path, &config).unwrap();

      let backups = list_backups(&path, &backup_dir).unwrap();
      assert_eq!(backups.len(), 1);
      assert_eq!(fs::read_to_string(&backups[0]).unwrap(), "old content\n");
    }

    #[test]
    fn it_skips_backup_for_new_file() {
      let dir = tempfile::tempdir().unwrap();
      let path = dir.path().join("test.md");
      let backup_dir = dir.path().join("backups");

      let mut config = Config::default();
      config.backup_dir = backup_dir.clone();
      config.doing_file_sort = SortOrder::Asc;

      write_with_backup(&sample_doc(), &path, &config).unwrap();

      assert!(path.exists());
      assert!(!backup_dir.exists());
    }

    #[test]
    fn it_writes_document_content() {
      let dir = tempfile::tempdir().unwrap();
      let path = dir.path().join("test.md");

      let mut config = Config::default();
      config.backup_dir = dir.path().join("backups");
      config.doing_file_sort = SortOrder::Asc;

      write_with_backup(&sample_doc(), &path, &config).unwrap();

      let content = fs::read_to_string(&path).unwrap();
      assert!(content.contains("Currently:"));
      assert!(content.contains("Test task"));
    }
  }
}