//! Plugin loader for discovering and loading plugins from the filesystem

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

use anyhow::{Result, anyhow};
use pinakes_plugin_api::PluginManifest;
use tracing::{debug, info, warn};
use walkdir::WalkDir;

/// Plugin loader handles discovery and loading of plugins from directories
pub struct PluginLoader {
  /// Directories to search for plugins
  plugin_dirs: Vec<PathBuf>,
}

impl PluginLoader {
  /// Create a new plugin loader
  #[must_use]
  pub const fn new(plugin_dirs: Vec<PathBuf>) -> Self {
    Self { plugin_dirs }
  }

  /// Discover all plugins in configured directories
  ///
  /// # Errors
  ///
  /// Returns an error if a plugin directory cannot be searched.
  pub fn discover_plugins(&self) -> Result<Vec<PluginManifest>> {
    let mut manifests = Vec::new();

    for dir in &self.plugin_dirs {
      if !dir.exists() {
        warn!("Plugin directory does not exist: {:?}", dir);
        continue;
      }

      info!("Discovering plugins in: {:?}", dir);

      let found = Self::discover_in_directory(dir);
      info!("Found {} plugins in {:?}", found.len(), dir);
      manifests.extend(found);
    }

    Ok(manifests)
  }

  /// Discover plugins in a specific directory
  fn discover_in_directory(dir: &Path) -> Vec<PluginManifest> {
    let mut manifests = Vec::new();

    // Walk the directory looking for plugin.toml files
    for entry in WalkDir::new(dir)
            .max_depth(3) // Don't go too deep
            .follow_links(false)
    {
      let entry = match entry {
        Ok(e) => e,
        Err(e) => {
          warn!("Error reading directory entry: {}", e);
          continue;
        },
      };

      let path = entry.path();

      // Look for plugin.toml files
      if path.file_name() == Some(std::ffi::OsStr::new("plugin.toml")) {
        debug!("Found plugin manifest: {:?}", path);

        match PluginManifest::from_file(path) {
          Ok(manifest) => {
            info!("Loaded manifest for plugin: {}", manifest.plugin.name);
            manifests.push(manifest);
          },
          Err(e) => {
            warn!("Failed to load manifest from {:?}: {}", path, e);
          },
        }
      }
    }

    manifests
  }

  /// Resolve the WASM binary path from a manifest
  ///
  /// # Errors
  ///
  /// Returns an error if the WASM binary is not found or its path escapes the
  /// plugin directory.
  pub fn resolve_wasm_path(
    &self,
    manifest: &PluginManifest,
  ) -> Result<PathBuf> {
    // The WASM path in the manifest is relative to the manifest file
    // We need to search for it in the plugin directories

    for dir in &self.plugin_dirs {
      // Look for a directory matching the plugin name
      let plugin_dir = dir.join(&manifest.plugin.name);
      if !plugin_dir.exists() {
        continue;
      }

      // Check for plugin.toml in this directory
      let manifest_path = plugin_dir.join("plugin.toml");
      if !manifest_path.exists() {
        continue;
      }

      // Resolve WASM path relative to this directory
      let wasm_path = plugin_dir.join(&manifest.plugin.binary.wasm);
      if wasm_path.exists() {
        // Verify the resolved path is within the plugin directory (prevent path
        // traversal)
        let canonical_wasm = wasm_path
          .canonicalize()
          .map_err(|e| anyhow!("Failed to canonicalize WASM path: {e}"))?;
        let canonical_plugin_dir = plugin_dir
          .canonicalize()
          .map_err(|e| anyhow!("Failed to canonicalize plugin dir: {e}"))?;
        if !canonical_wasm.starts_with(&canonical_plugin_dir) {
          return Err(anyhow!(
            "WASM binary path escapes plugin directory: {}",
            wasm_path.display()
          ));
        }
        return Ok(canonical_wasm);
      }
    }

    Err(anyhow!(
      "WASM binary not found for plugin: {}",
      manifest.plugin.name
    ))
  }

  /// Download a plugin from a URL
  ///
  /// # Errors
  ///
  /// Returns an error if the URL is not HTTPS, no plugin directories are
  /// configured, the download fails, the archive is too large, or extraction
  /// fails.
  pub async fn download_plugin(&self, url: &str) -> Result<PathBuf> {
    const MAX_PLUGIN_SIZE: u64 = 100 * 1024 * 1024; // 100 MB

    // Only allow HTTPS downloads
    if !url.starts_with("https://") {
      return Err(anyhow!(
        "Only HTTPS URLs are allowed for plugin downloads: {url}"
      ));
    }

    let dest_dir = self
      .plugin_dirs
      .first()
      .ok_or_else(|| anyhow!("No plugin directories configured"))?;

    std::fs::create_dir_all(dest_dir)?;

    // Download the archive with timeout and size limits
    let client = reqwest::Client::builder()
      .timeout(std::time::Duration::from_mins(5))
      .build()
      .map_err(|e| anyhow!("Failed to build HTTP client: {e}"))?;

    let response = client
      .get(url)
      .send()
      .await
      .map_err(|e| anyhow!("Failed to download plugin: {e}"))?;

    if !response.status().is_success() {
      return Err(anyhow!(
        "Plugin download failed with status: {}",
        response.status()
      ));
    }

    // Check content-length header before downloading
    if let Some(content_length) = response.content_length()
      && content_length > MAX_PLUGIN_SIZE
    {
      return Err(anyhow!(
        "Plugin archive too large: {content_length} bytes (max \
         {MAX_PLUGIN_SIZE} bytes)"
      ));
    }

    let bytes = response
      .bytes()
      .await
      .map_err(|e| anyhow!("Failed to read plugin response: {e}"))?;

    // Check actual size after download
    if bytes.len() as u64 > MAX_PLUGIN_SIZE {
      return Err(anyhow!(
        "Plugin archive too large: {} bytes (max {} bytes)",
        bytes.len(),
        MAX_PLUGIN_SIZE
      ));
    }

    // Write archive to a unique temp file
    let temp_archive =
      dest_dir.join(format!(".download-{}.tar.gz", uuid::Uuid::now_v7()));
    std::fs::write(&temp_archive, &bytes)?;

    // Extract using tar with -C to target directory
    let canonical_dest = dest_dir
      .canonicalize()
      .map_err(|e| anyhow!("Failed to canonicalize dest dir: {e}"))?;
    let output = std::process::Command::new("tar")
      .args([
        "xzf",
        &temp_archive.to_string_lossy(),
        "-C",
        &canonical_dest.to_string_lossy(),
      ])
      .output()
      .map_err(|e| anyhow!("Failed to extract plugin archive: {e}"))?;

    // Clean up the archive
    let _ = std::fs::remove_file(&temp_archive);

    if !output.status.success() {
      return Err(anyhow!(
        "Failed to extract plugin archive: {}",
        String::from_utf8_lossy(&output.stderr)
      ));
    }

    // Validate that all extracted files are within dest_dir
    for entry in WalkDir::new(&canonical_dest).follow_links(false) {
      let entry = entry?;
      let entry_canonical = entry.path().canonicalize()?;
      if !entry_canonical.starts_with(&canonical_dest) {
        return Err(anyhow!(
          "Extracted file escapes destination directory: {}",
          entry.path().display()
        ));
      }
    }

    // Find the extracted plugin directory by looking for plugin.toml
    for entry in WalkDir::new(dest_dir).max_depth(2).follow_links(false) {
      let entry = entry?;
      if entry.file_name() == "plugin.toml" {
        let plugin_dir = entry
          .path()
          .parent()
          .ok_or_else(|| anyhow!("Invalid plugin.toml location"))?;

        // Validate the manifest
        let manifest = PluginManifest::from_file(entry.path())?;
        info!("Downloaded and extracted plugin: {}", manifest.plugin.name);

        return Ok(plugin_dir.to_path_buf());
      }
    }

    Err(anyhow!(
      "No plugin.toml found after extracting archive from: {url}"
    ))
  }

  /// Validate a plugin package
  ///
  /// # Errors
  ///
  /// Returns an error if the path does not exist, is missing `plugin.toml`,
  /// the WASM binary is not found, or the WASM file is invalid.
  pub fn validate_plugin_package(&self, path: &Path) -> Result<()> {
    // Check that the path exists
    if !path.exists() {
      return Err(anyhow!("Plugin path does not exist: {}", path.display()));
    }

    // Check for plugin.toml
    let manifest_path = path.join("plugin.toml");
    if !manifest_path.exists() {
      return Err(anyhow!("Missing plugin.toml in {}", path.display()));
    }

    // Parse and validate manifest
    let manifest = PluginManifest::from_file(&manifest_path)?;

    // Check that WASM binary exists
    let wasm_path = path.join(&manifest.plugin.binary.wasm);
    if !wasm_path.exists() {
      return Err(anyhow!(
        "WASM binary not found: {}",
        manifest.plugin.binary.wasm
      ));
    }

    // Verify the WASM path is within the plugin directory (prevent path
    // traversal)
    let canonical_wasm = wasm_path.canonicalize()?;
    let canonical_path = path.canonicalize()?;
    if !canonical_wasm.starts_with(&canonical_path) {
      return Err(anyhow!(
        "WASM binary path escapes plugin directory: {}",
        wasm_path.display()
      ));
    }

    // Validate WASM file
    let wasm_bytes = std::fs::read(&wasm_path)?;
    if wasm_bytes.len() < 4 || &wasm_bytes[0..4] != b"\0asm" {
      return Err(anyhow!("Invalid WASM file: {}", wasm_path.display()));
    }

    Ok(())
  }

  /// Get plugin directory path for a given plugin name
  #[must_use]
  pub fn get_plugin_dir(&self, plugin_name: &str) -> Option<PathBuf> {
    for dir in &self.plugin_dirs {
      let plugin_dir = dir.join(plugin_name);
      if plugin_dir.exists() {
        return Some(plugin_dir);
      }
    }
    None
  }
}

#[cfg(test)]
mod tests {
  use tempfile::TempDir;

  use super::*;

  #[test]
  fn test_discover_plugins_empty() {
    let temp_dir = TempDir::new().unwrap();
    let loader = PluginLoader::new(vec![temp_dir.path().to_path_buf()]);

    let manifests = loader.discover_plugins().unwrap();
    assert_eq!(manifests.len(), 0);
  }

  #[test]
  fn test_discover_plugins_with_manifest() {
    let temp_dir = TempDir::new().unwrap();
    let plugin_dir = temp_dir.path().join("test-plugin");
    std::fs::create_dir(&plugin_dir).unwrap();

    // Create a valid manifest
    let manifest_content = r#"
[plugin]
name = "test-plugin"
version = "1.0.0"
api_version = "1.0"
kind = ["media_type"]

[plugin.binary]
wasm = "plugin.wasm"
"#;
    std::fs::write(plugin_dir.join("plugin.toml"), manifest_content).unwrap();

    // Create dummy WASM file
    std::fs::write(plugin_dir.join("plugin.wasm"), b"\0asm\x01\x00\x00\x00")
      .unwrap();

    let loader = PluginLoader::new(vec![temp_dir.path().to_path_buf()]);
    let manifests = loader.discover_plugins().unwrap();

    assert_eq!(manifests.len(), 1);
    assert_eq!(manifests[0].plugin.name, "test-plugin");
  }

  #[test]
  fn test_validate_plugin_package() {
    let temp_dir = TempDir::new().unwrap();
    let plugin_dir = temp_dir.path().join("test-plugin");
    std::fs::create_dir(&plugin_dir).unwrap();

    // Create a valid manifest
    let manifest_content = r#"
[plugin]
name = "test-plugin"
version = "1.0.0"
api_version = "1.0"
kind = ["media_type"]

[plugin.binary]
wasm = "plugin.wasm"
"#;
    std::fs::write(plugin_dir.join("plugin.toml"), manifest_content).unwrap();

    let loader = PluginLoader::new(vec![]);

    // Should fail without WASM file
    assert!(loader.validate_plugin_package(&plugin_dir).is_err());

    // Create valid WASM file (magic number only)
    std::fs::write(plugin_dir.join("plugin.wasm"), b"\0asm\x01\x00\x00\x00")
      .unwrap();

    // Should succeed now
    assert!(loader.validate_plugin_package(&plugin_dir).is_ok());
  }

  #[test]
  fn test_validate_invalid_wasm() {
    let temp_dir = TempDir::new().unwrap();
    let plugin_dir = temp_dir.path().join("test-plugin");
    std::fs::create_dir(&plugin_dir).unwrap();

    let manifest_content = r#"
[plugin]
name = "test-plugin"
version = "1.0.0"
api_version = "1.0"
kind = ["media_type"]

[plugin.binary]
wasm = "plugin.wasm"
"#;
    std::fs::write(plugin_dir.join("plugin.toml"), manifest_content).unwrap();

    // Create invalid WASM file
    std::fs::write(plugin_dir.join("plugin.wasm"), b"not wasm").unwrap();

    let loader = PluginLoader::new(vec![]);
    assert!(loader.validate_plugin_package(&plugin_dir).is_err());
  }
}