use std::{
  path::{Path, PathBuf},
  sync::Arc,
  time::SystemTime,
};

use tracing::info;

use crate::{
  audit,
  error::{PinakesError, Result},
  hash::compute_file_hash,
  links,
  media_type::{BuiltinMediaType, MediaType},
  metadata,
  model::{
    AuditAction,
    CustomField,
    CustomFieldType,
    MediaId,
    MediaItem,
    StorageMode,
  },
  plugin::PluginPipeline,
  storage::DynStorageBackend,
  thumbnail,
};

/// Result of importing a single file.
pub struct ImportResult {
  pub media_id:      MediaId,
  pub was_duplicate: bool,
  /// True if the file was skipped because it hasn't changed since last scan
  pub was_skipped:   bool,
  pub path:          PathBuf,
}

/// Options for import operations
#[derive(Debug, Clone, Default)]
pub struct ImportOptions {
  /// Skip files that haven't changed since last scan (based on mtime)
  pub incremental:  bool,
  /// Force re-import even if mtime hasn't changed
  pub force:        bool,
  /// Photo configuration for toggleable features
  pub photo_config: crate::config::PhotoConfig,
}

/// Get the modification time of a file as a Unix timestamp
fn get_file_mtime(path: &Path) -> Option<i64> {
  std::fs::metadata(path)
    .ok()
    .and_then(|m| m.modified().ok())
    .and_then(|t| t.duration_since(SystemTime::UNIX_EPOCH).ok())
    .map(|d| i64::try_from(d.as_secs()).unwrap_or(i64::MAX))
}

/// Validates that a path is within configured root directories.
///
/// # Arguments
///
/// * `storage` - Storage backend to query root directories
/// * `path` - Path to validate
///
/// # Returns
///
/// `Ok(())` if path is within roots or no roots configured
///
/// # Errors
///
/// Returns `InvalidOperation` if path is outside all root directories
pub async fn validate_path_in_roots(
  storage: &DynStorageBackend,
  path: &Path,
) -> Result<()> {
  let roots = storage.list_root_dirs().await?;
  if roots.is_empty() {
    return Ok(());
  }
  for root in &roots {
    if let Ok(canonical_root) = root.canonicalize()
      && path.starts_with(&canonical_root)
    {
      return Ok(());
    }
  }
  Err(PinakesError::InvalidOperation(format!(
    "path {} is not within any configured root directory",
    path.display()
  )))
}

/// Imports a file using default options.
///
/// # Arguments
///
/// * `storage` - Storage backend
/// * `path` - Path to the file to import
///
/// # Returns
///
/// Import result with media ID and status
///
/// # Errors
///
/// Returns `FileNotFound` if path doesn't exist
pub async fn import_file(
  storage: &DynStorageBackend,
  path: &Path,
  pipeline: Option<&Arc<PluginPipeline>>,
) -> Result<ImportResult> {
  import_file_with_options(storage, path, &ImportOptions::default(), pipeline)
    .await
}

/// Import a file with configurable options for incremental scanning
///
/// # Errors
///
/// Returns [`PinakesError`] if the file cannot be read, hashed, or stored.
pub async fn import_file_with_options(
  storage: &DynStorageBackend,
  path: &Path,
  options: &ImportOptions,
  pipeline: Option<&Arc<PluginPipeline>>,
) -> Result<ImportResult> {
  let path = path.canonicalize()?;

  if !path.exists() {
    return Err(PinakesError::FileNotFound(path));
  }

  validate_path_in_roots(storage, &path).await?;

  let media_type = if let Some(pl) = pipeline {
    pl.resolve_media_type(&path).await
  } else {
    MediaType::from_path(&path)
  }
  .ok_or_else(|| PinakesError::UnsupportedMediaType(path.clone()))?;

  let current_mtime = get_file_mtime(&path);

  // Check for incremental scan: skip if file hasn't changed
  if options.incremental
    && !options.force
    && let Some(existing) = storage.get_media_by_path(&path).await?
    && let (Some(stored_mtime), Some(curr_mtime)) =
      (existing.file_mtime, current_mtime)
    && stored_mtime == curr_mtime
  {
    return Ok(ImportResult {
      media_id:      existing.id,
      was_duplicate: false,
      was_skipped:   true,
      path:          path.clone(),
    });
  }

  let content_hash = compute_file_hash(&path).await?;

  if let Some(existing) = storage.get_media_by_hash(&content_hash).await? {
    // Update the mtime even for duplicates so incremental scan works
    if current_mtime.is_some() && existing.file_mtime != current_mtime {
      let mut updated = existing.clone();
      updated.file_mtime = current_mtime;
      let _ = storage.update_media(&updated).await;
    }
    return Ok(ImportResult {
      media_id:      existing.id,
      was_duplicate: true,
      was_skipped:   false,
      path:          path.clone(),
    });
  }

  let file_meta = std::fs::metadata(&path)?;
  let file_size = file_meta.len();

  let extracted = if let Some(pl) = pipeline {
    pl.extract_metadata(&path, &media_type).await?
  } else {
    let path_clone = path.clone();
    let media_type_clone = media_type.clone();
    tokio::task::spawn_blocking(move || {
      metadata::extract_metadata(&path_clone, &media_type_clone)
    })
    .await
    .map_err(|e| PinakesError::MetadataExtraction(e.to_string()))??
  };

  let file_name = path
    .file_name()
    .unwrap_or_default()
    .to_string_lossy()
    .to_string();

  let now = chrono::Utc::now();
  let media_id = MediaId::new();

  // Generate thumbnail for image types
  let thumb_path = if let Some(pl) = pipeline {
    pl.generate_thumbnail(
      media_id,
      &path,
      &media_type,
      &thumbnail::default_thumbnail_dir(),
    )
    .await?
  } else {
    let source = path.clone();
    let thumb_dir = thumbnail::default_thumbnail_dir();
    let media_type_clone = media_type.clone();
    tokio::task::spawn_blocking(move || {
      thumbnail::generate_thumbnail(
        media_id,
        &source,
        &media_type_clone,
        &thumb_dir,
      )
    })
    .await
    .map_err(|e| PinakesError::MetadataExtraction(e.to_string()))??
  };

  // Generate perceptual hash for image files (if enabled in config)
  let perceptual_hash = if options.photo_config.generate_perceptual_hash()
    && media_type.category() == crate::media_type::MediaCategory::Image
  {
    crate::metadata::image::generate_perceptual_hash(&path)
  } else {
    None
  };

  // Check if this is a markdown file for link extraction
  let is_markdown =
    media_type == MediaType::Builtin(BuiltinMediaType::Markdown);

  // Capture media type debug string before moving into MediaItem
  let media_type_debug = format!("{media_type:?}");

  let item = MediaItem {
    id: media_id,
    path: path.clone(),
    file_name,
    media_type,
    content_hash,
    file_size,
    title: extracted.title,
    artist: extracted.artist,
    album: extracted.album,
    genre: extracted.genre,
    year: extracted.year,
    duration_secs: extracted.duration_secs,
    description: extracted.description,
    thumbnail_path: thumb_path,
    custom_fields: std::collections::HashMap::new(),
    file_mtime: current_mtime,

    // Photo-specific metadata from extraction
    date_taken: extracted.date_taken,
    latitude: extracted.latitude,
    longitude: extracted.longitude,
    camera_make: extracted.camera_make,
    camera_model: extracted.camera_model,
    rating: extracted.rating,
    perceptual_hash,

    // Managed storage fields - external files use defaults
    storage_mode: StorageMode::External,
    original_filename: None,
    uploaded_at: None,
    storage_key: None,

    created_at: now,
    updated_at: now,

    // New items are not deleted
    deleted_at: None,

    // Links will be extracted separately
    links_extracted_at: None,
  };

  storage.insert_media(&item).await?;

  // Extract and store markdown links for markdown files
  if is_markdown
    && let Err(e) = extract_and_store_links(storage, media_id, &path).await
  {
    tracing::warn!(
        media_id = %media_id,
        path = %path.display(),
        error = %e,
        "failed to extract markdown links"
    );
  }

  // Store extracted extra metadata as custom fields
  for (key, value) in &extracted.extra {
    let field = CustomField {
      field_type: CustomFieldType::Text,
      value:      value.clone(),
    };
    if let Err(e) = storage.set_custom_field(media_id, key, &field).await {
      tracing::warn!(
          media_id = %media_id,
          field = %key,
          error = %e,
          "failed to store extracted metadata as custom field"
      );
    }
  }

  audit::record_action(
    storage,
    Some(media_id),
    AuditAction::Imported,
    Some(format!("path={}", path.display())),
  )
  .await?;

  if let Some(pl) = pipeline {
    let payload = serde_json::json!({
        "media_id": media_id.to_string(),
        "path": path.to_string_lossy(),
        "media_type": media_type_debug,
    });
    pl.emit_event("MediaImported", &payload);
  }

  info!(media_id = %media_id, path = %path.display(), "imported media file");

  Ok(ImportResult {
    media_id,
    was_duplicate: false,
    was_skipped: false,
    path: path.clone(),
  })
}

pub(crate) fn should_ignore(
  path: &std::path::Path,
  patterns: &[String],
) -> bool {
  for component in path.components() {
    if let std::path::Component::Normal(name) = component {
      let name_str = name.to_string_lossy();
      for pattern in patterns {
        if pattern.starts_with('.')
          && name_str.starts_with('.')
          && pattern == name_str.as_ref()
        {
          return true;
        }
        // Simple glob: ".*" matches any dotfile
        if pattern == ".*" && name_str.starts_with('.') {
          return true;
        }
        if name_str == pattern.as_str() {
          return true;
        }
      }
    }
  }
  false
}

/// Default number of concurrent import tasks.
const DEFAULT_IMPORT_CONCURRENCY: usize = 8;

/// Import all supported files in a directory with default options.
///
/// # Errors
///
/// Returns [`PinakesError`] if the directory cannot be read or spawned tasks
/// fail.
pub async fn import_directory(
  storage: &DynStorageBackend,
  dir: &Path,
  ignore_patterns: &[String],
  pipeline: Option<&Arc<PluginPipeline>>,
) -> Result<Vec<std::result::Result<ImportResult, PinakesError>>> {
  import_directory_with_options(
    storage,
    dir,
    ignore_patterns,
    DEFAULT_IMPORT_CONCURRENCY,
    &ImportOptions::default(),
    pipeline,
  )
  .await
}

/// Import all supported files in a directory with a specified concurrency
/// limit.
///
/// # Errors
///
/// Returns [`PinakesError`] if the directory cannot be read or spawned tasks
/// fail.
pub async fn import_directory_with_concurrency(
  storage: &DynStorageBackend,
  dir: &Path,
  ignore_patterns: &[String],
  concurrency: usize,
  pipeline: Option<&Arc<PluginPipeline>>,
) -> Result<Vec<std::result::Result<ImportResult, PinakesError>>> {
  import_directory_with_options(
    storage,
    dir,
    ignore_patterns,
    concurrency,
    &ImportOptions::default(),
    pipeline,
  )
  .await
}

/// Import a directory with full options including incremental scanning support.
///
/// # Errors
///
/// Returns [`PinakesError`] if the directory cannot be read or spawned tasks
/// fail.
pub async fn import_directory_with_options(
  storage: &DynStorageBackend,
  dir: &Path,
  ignore_patterns: &[String],
  concurrency: usize,
  options: &ImportOptions,
  pipeline: Option<&Arc<PluginPipeline>>,
) -> Result<Vec<std::result::Result<ImportResult, PinakesError>>> {
  let concurrency = concurrency.clamp(1, 256);
  let dir = dir.to_path_buf();
  let patterns = ignore_patterns.to_vec();
  let options = options.clone();
  let pipeline = pipeline.cloned();

  let entries: Vec<PathBuf> = {
    let dir = dir.clone();
    tokio::task::spawn_blocking(move || {
      walkdir::WalkDir::new(&dir)
        .follow_links(true)
        .into_iter()
        .filter_map(std::result::Result::ok)
        .filter(|e| !e.file_type().is_dir())
        .filter(|e| MediaType::from_path(e.path()).is_some())
        .filter(|e| !should_ignore(e.path(), &patterns))
        .map(|e| e.path().to_path_buf())
        .collect()
    })
    .await
    .map_err(|e| PinakesError::Io(std::io::Error::other(e)))?
  };

  let mut results = Vec::with_capacity(entries.len());
  let mut join_set = tokio::task::JoinSet::new();

  for entry_path in entries {
    let storage = Arc::clone(storage);
    let path = entry_path.clone();
    let opts = options.clone();
    let pl = pipeline.clone();

    join_set.spawn(async move {
      let result =
        import_file_with_options(&storage, &path, &opts, pl.as_ref()).await;
      (path, result)
    });

    // Limit concurrency by draining when we hit the cap
    if join_set.len() >= concurrency
      && let Some(result) = join_set.join_next().await
    {
      collect_import_result(result, &mut results);
    }
  }

  // Drain remaining tasks
  while let Some(result) = join_set.join_next().await {
    collect_import_result(result, &mut results);
  }

  Ok(results)
}

fn collect_import_result(
  join_result: std::result::Result<
    (PathBuf, Result<ImportResult>),
    tokio::task::JoinError,
  >,
  results: &mut Vec<std::result::Result<ImportResult, PinakesError>>,
) {
  match join_result {
    Ok((_path, Ok(r))) => results.push(Ok(r)),
    Ok((path, Err(e))) => {
      tracing::warn!(path = %path.display(), error = %e, "failed to import file");
      results.push(Err(e));
    },
    Err(join_err) => {
      if join_err.is_panic() {
        tracing::error!(error = %join_err, "import task panicked");
      } else {
        tracing::warn!(error = %join_err, "import task was cancelled");
      }
      results.push(Err(PinakesError::InvalidOperation(format!(
        "import task failed: {join_err}"
      ))));
    },
  }
}

/// Extract markdown links from a file and store them in the database.
async fn extract_and_store_links(
  storage: &DynStorageBackend,
  media_id: MediaId,
  path: &Path,
) -> Result<()> {
  let content = tokio::fs::read_to_string(path).await.map_err(|e| {
    PinakesError::Io(std::io::Error::other(format!(
      "failed to read markdown file for link extraction: {e}"
    )))
  })?;

  // Extract links
  let extracted_links = links::extract_links(media_id, &content);

  if extracted_links.is_empty() {
    // No links found, just mark as extracted
    storage.mark_links_extracted(media_id).await?;
    return Ok(());
  }

  // Clear any existing links for this media (in case of re-import)
  storage.clear_links_for_media(media_id).await?;

  // Save extracted links
  storage
    .save_markdown_links(media_id, &extracted_links)
    .await?;

  // Mark links as extracted
  storage.mark_links_extracted(media_id).await?;

  tracing::debug!(
      media_id = %media_id,
      link_count = extracted_links.len(),
      "extracted markdown links"
  );

  Ok(())
}