//! Capability-based security for plugins

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

use anyhow::{Result, anyhow};
use pinakes_plugin_api::Capabilities;

/// Capability enforcer validates and enforces plugin capabilities
pub struct CapabilityEnforcer {
  /// Maximum allowed memory per plugin (bytes)
  max_memory_limit: usize,

  /// Maximum allowed CPU time per plugin (milliseconds)
  max_cpu_time_limit: u64,

  /// Allowed filesystem read paths (system-wide)
  allowed_read_paths: Vec<PathBuf>,

  /// Allowed filesystem write paths (system-wide)
  allowed_write_paths: Vec<PathBuf>,

  /// Whether to allow network access by default
  allow_network_default: bool,
}

impl CapabilityEnforcer {
  /// Create a new capability enforcer with default limits
  #[must_use]
  pub const fn new() -> Self {
    Self {
      max_memory_limit:      512 * 1024 * 1024, // 512 MB
      max_cpu_time_limit:    60 * 1000,         // 60 seconds
      allowed_read_paths:    vec![],
      allowed_write_paths:   vec![],
      allow_network_default: false,
    }
  }

  /// Set maximum memory limit
  #[must_use]
  pub const fn with_max_memory(mut self, bytes: usize) -> Self {
    self.max_memory_limit = bytes;
    self
  }

  /// Set maximum CPU time limit
  #[must_use]
  pub const fn with_max_cpu_time(mut self, milliseconds: u64) -> Self {
    self.max_cpu_time_limit = milliseconds;
    self
  }

  /// Add allowed read path
  #[must_use]
  pub fn allow_read_path(mut self, path: PathBuf) -> Self {
    self.allowed_read_paths.push(path);
    self
  }

  /// Add allowed write path
  #[must_use]
  pub fn allow_write_path(mut self, path: PathBuf) -> Self {
    self.allowed_write_paths.push(path);
    self
  }

  /// Set default network access policy
  #[must_use]
  pub const fn with_network_default(mut self, allow: bool) -> Self {
    self.allow_network_default = allow;
    self
  }

  /// Validate capabilities requested by a plugin
  ///
  /// # Errors
  ///
  /// Returns an error if the plugin requests capabilities that exceed the
  /// configured system limits, such as memory, CPU time, filesystem paths, or
  /// network access.
  pub fn validate_capabilities(
    &self,
    capabilities: &Capabilities,
  ) -> Result<()> {
    // Validate memory limit
    if let Some(memory) = capabilities.max_memory_bytes
      && memory > self.max_memory_limit
    {
      return Err(anyhow!(
        "Requested memory ({} bytes) exceeds limit ({} bytes)",
        memory,
        self.max_memory_limit
      ));
    }

    // Validate CPU time limit
    if let Some(cpu_time) = capabilities.max_cpu_time_ms
      && cpu_time > self.max_cpu_time_limit
    {
      return Err(anyhow!(
        "Requested CPU time ({} ms) exceeds limit ({} ms)",
        cpu_time,
        self.max_cpu_time_limit
      ));
    }

    // Validate filesystem access
    self.validate_filesystem_access(capabilities)?;

    // Validate network access
    if capabilities.network.enabled && !self.allow_network_default {
      return Err(anyhow!(
        "Plugin requests network access, but network access is disabled by \
         policy"
      ));
    }

    Ok(())
  }

  /// Validate filesystem access capabilities
  fn validate_filesystem_access(
    &self,
    capabilities: &Capabilities,
  ) -> Result<()> {
    // Check read paths
    for path in &capabilities.filesystem.read {
      if !self.is_read_allowed(path) {
        return Err(anyhow!(
          "Plugin requests read access to {} which is not in allowed paths",
          path.display()
        ));
      }
    }

    // Check write paths
    for path in &capabilities.filesystem.write {
      if !self.is_write_allowed(path) {
        return Err(anyhow!(
          "Plugin requests write access to {} which is not in allowed paths",
          path.display()
        ));
      }
    }

    Ok(())
  }

  /// Check if a path is allowed for reading
  #[must_use]
  pub fn is_read_allowed(&self, path: &Path) -> bool {
    if self.allowed_read_paths.is_empty() {
      return false; // deny-all when unconfigured
    }
    let Ok(canonical) = path.canonicalize() else {
      return false;
    };
    self.allowed_read_paths.iter().any(|allowed| {
      allowed
        .canonicalize()
        .is_ok_and(|a| canonical.starts_with(a))
    })
  }

  /// Check if a path is allowed for writing
  #[must_use]
  pub fn is_write_allowed(&self, path: &Path) -> bool {
    if self.allowed_write_paths.is_empty() {
      return false; // deny-all when unconfigured
    }
    let canonical = if path.exists() {
      path.canonicalize().ok()
    } else {
      path
        .parent()
        .and_then(|p| p.canonicalize().ok())
        .map(|p| p.join(path.file_name().unwrap_or_default()))
    };
    let Some(canonical) = canonical else {
      return false;
    };
    self.allowed_write_paths.iter().any(|allowed| {
      allowed
        .canonicalize()
        .is_ok_and(|a| canonical.starts_with(a))
    })
  }

  /// Check if network access is allowed for a plugin
  #[must_use]
  pub const fn is_network_allowed(&self, capabilities: &Capabilities) -> bool {
    capabilities.network.enabled && self.allow_network_default
  }

  /// Check if a specific domain is allowed
  #[must_use]
  pub fn is_domain_allowed(
    &self,
    capabilities: &Capabilities,
    domain: &str,
  ) -> bool {
    if !capabilities.network.enabled {
      return false;
    }

    // If no domain restrictions, allow all domains
    if capabilities.network.allowed_domains.is_none() {
      return self.allow_network_default;
    }

    // Check against allowed domains list
    capabilities
      .network
      .allowed_domains
      .as_ref()
      .is_some_and(|domains| {
        domains.iter().any(|d| d.eq_ignore_ascii_case(domain))
      })
  }

  /// Get effective memory limit for a plugin
  #[must_use]
  pub fn get_memory_limit(&self, capabilities: &Capabilities) -> usize {
    capabilities
      .max_memory_bytes
      .unwrap_or(self.max_memory_limit)
      .min(self.max_memory_limit)
  }

  /// Get effective CPU time limit for a plugin
  #[must_use]
  pub fn get_cpu_time_limit(&self, capabilities: &Capabilities) -> u64 {
    capabilities
      .max_cpu_time_ms
      .unwrap_or(self.max_cpu_time_limit)
      .min(self.max_cpu_time_limit)
  }

  /// Validate that a function call is allowed for a plugin's declared kinds.
  ///
  /// Defense-in-depth: even though the pipeline filters by kind, this prevents
  /// bugs from calling wrong functions on plugins. Returns `true` if allowed.
  #[must_use]
  pub fn validate_function_call(
    &self,
    plugin_kinds: &[String],
    function_name: &str,
  ) -> bool {
    match function_name {
      // Lifecycle functions are always allowed
      "initialize" | "shutdown" | "health_check" => true,
      // MediaTypeProvider
      "supported_media_types" | "can_handle" => {
        plugin_kinds.iter().any(|k| k == "media_type")
      },
      // supported_types is shared by metadata_extractor and thumbnail_generator
      "supported_types" => {
        plugin_kinds
          .iter()
          .any(|k| k == "metadata_extractor" || k == "thumbnail_generator")
      },
      // MetadataExtractor
      "extract_metadata" => {
        plugin_kinds.iter().any(|k| k == "metadata_extractor")
      },
      // ThumbnailGenerator
      "generate_thumbnail" => {
        plugin_kinds.iter().any(|k| k == "thumbnail_generator")
      },
      // SearchBackend
      "search" | "index_item" | "remove_item" | "get_stats" => {
        plugin_kinds.iter().any(|k| k == "search_backend")
      },
      // EventHandler
      "interested_events" | "handle_event" => {
        plugin_kinds.iter().any(|k| k == "event_handler")
      },
      // ThemeProvider
      "get_themes" | "load_theme" => {
        plugin_kinds.iter().any(|k| k == "theme_provider")
      },
      // Unknown function names are not allowed
      _ => false,
    }
  }
}

impl Default for CapabilityEnforcer {
  fn default() -> Self {
    Self::new()
  }
}

#[cfg(test)]
mod tests {
  #[allow(unused_imports)]
  use pinakes_plugin_api::{FilesystemCapability, NetworkCapability};

  use super::*;

  #[test]
  fn test_validate_memory_limit() {
    let enforcer = CapabilityEnforcer::new().with_max_memory(100 * 1024 * 1024); // 100 MB

    let mut caps = Capabilities::default();
    caps.max_memory_bytes = Some(50 * 1024 * 1024); // 50 MB - OK
    assert!(enforcer.validate_capabilities(&caps).is_ok());

    caps.max_memory_bytes = Some(200 * 1024 * 1024); // 200 MB - exceeds limit
    assert!(enforcer.validate_capabilities(&caps).is_err());
  }

  #[test]
  fn test_validate_cpu_time_limit() {
    let enforcer = CapabilityEnforcer::new().with_max_cpu_time(30_000); // 30 seconds

    let mut caps = Capabilities::default();
    caps.max_cpu_time_ms = Some(10_000); // 10 seconds - OK
    assert!(enforcer.validate_capabilities(&caps).is_ok());

    caps.max_cpu_time_ms = Some(60_000); // 60 seconds - exceeds limit
    assert!(enforcer.validate_capabilities(&caps).is_err());
  }

  #[test]
  fn test_filesystem_read_allowed() {
    // Use real temp directories so canonicalize works
    let tmp = tempfile::tempdir().unwrap();
    let allowed_dir = tmp.path().join("allowed");
    std::fs::create_dir_all(&allowed_dir).unwrap();
    let test_file = allowed_dir.join("test.txt");
    std::fs::write(&test_file, "test").unwrap();

    let enforcer = CapabilityEnforcer::new().allow_read_path(allowed_dir);

    assert!(enforcer.is_read_allowed(&test_file));
    assert!(!enforcer.is_read_allowed(Path::new("/etc/passwd")));
  }

  #[test]
  fn test_filesystem_read_denied_when_empty() {
    let enforcer = CapabilityEnforcer::new();
    assert!(!enforcer.is_read_allowed(Path::new("/tmp/test.txt")));
  }

  #[test]
  fn test_filesystem_write_allowed() {
    let tmp = tempfile::tempdir().unwrap();
    let output_dir = tmp.path().join("output");
    std::fs::create_dir_all(&output_dir).unwrap();
    // Existing file in allowed dir
    let existing = output_dir.join("file.txt");
    std::fs::write(&existing, "test").unwrap();

    let enforcer =
      CapabilityEnforcer::new().allow_write_path(output_dir.clone());

    assert!(enforcer.is_write_allowed(&existing));
    // New file in allowed dir (parent exists)
    assert!(enforcer.is_write_allowed(&output_dir.join("new_file.txt")));
    assert!(!enforcer.is_write_allowed(Path::new("/etc/config")));
  }

  #[test]
  fn test_filesystem_write_denied_when_empty() {
    let enforcer = CapabilityEnforcer::new();
    assert!(!enforcer.is_write_allowed(Path::new("/tmp/file.txt")));
  }

  #[test]
  fn test_network_allowed() {
    let enforcer = CapabilityEnforcer::new().with_network_default(true);

    let mut caps = Capabilities::default();
    caps.network.enabled = true;

    assert!(enforcer.is_network_allowed(&caps));

    caps.network.enabled = false;
    assert!(!enforcer.is_network_allowed(&caps));
  }

  #[test]
  fn test_domain_restrictions() {
    let enforcer = CapabilityEnforcer::new().with_network_default(true);

    let mut caps = Capabilities::default();
    caps.network.enabled = true;
    caps.network.allowed_domains = Some(vec![
      "api.example.com".to_string(),
      "cdn.example.com".to_string(),
    ]);

    assert!(enforcer.is_domain_allowed(&caps, "api.example.com"));
    assert!(enforcer.is_domain_allowed(&caps, "cdn.example.com"));
    assert!(!enforcer.is_domain_allowed(&caps, "evil.com"));
  }

  #[test]
  fn test_get_effective_limits() {
    let enforcer = CapabilityEnforcer::new()
      .with_max_memory(100 * 1024 * 1024)
      .with_max_cpu_time(30_000);

    let mut caps = Capabilities::default();

    // No limits specified, use the defaults
    assert_eq!(enforcer.get_memory_limit(&caps), 100 * 1024 * 1024);
    assert_eq!(enforcer.get_cpu_time_limit(&caps), 30_000);

    // Plugin requests lower limits, use plugin's
    caps.max_memory_bytes = Some(50 * 1024 * 1024);
    caps.max_cpu_time_ms = Some(10_000);
    assert_eq!(enforcer.get_memory_limit(&caps), 50 * 1024 * 1024);
    assert_eq!(enforcer.get_cpu_time_limit(&caps), 10_000);

    // Plugin requests higher limits, cap at system max
    caps.max_memory_bytes = Some(200 * 1024 * 1024);
    caps.max_cpu_time_ms = Some(60_000);
    assert_eq!(enforcer.get_memory_limit(&caps), 100 * 1024 * 1024);
    assert_eq!(enforcer.get_cpu_time_limit(&caps), 30_000);
  }

  #[test]
  fn test_validate_function_call_lifecycle_always_allowed() {
    let enforcer = CapabilityEnforcer::new();
    let kinds = vec!["metadata_extractor".to_string()];
    assert!(enforcer.validate_function_call(&kinds, "initialize"));
    assert!(enforcer.validate_function_call(&kinds, "shutdown"));
    assert!(enforcer.validate_function_call(&kinds, "health_check"));
  }

  #[test]
  fn test_validate_function_call_metadata_extractor() {
    let enforcer = CapabilityEnforcer::new();
    let kinds = vec!["metadata_extractor".to_string()];
    assert!(enforcer.validate_function_call(&kinds, "extract_metadata"));
    assert!(enforcer.validate_function_call(&kinds, "supported_types"));
    assert!(!enforcer.validate_function_call(&kinds, "search"));
    assert!(!enforcer.validate_function_call(&kinds, "generate_thumbnail"));
    assert!(!enforcer.validate_function_call(&kinds, "can_handle"));
  }

  #[test]
  fn test_validate_function_call_multi_kind() {
    let enforcer = CapabilityEnforcer::new();
    let kinds =
      vec!["media_type".to_string(), "metadata_extractor".to_string()];
    assert!(enforcer.validate_function_call(&kinds, "can_handle"));
    assert!(enforcer.validate_function_call(&kinds, "supported_media_types"));
    assert!(enforcer.validate_function_call(&kinds, "extract_metadata"));
    assert!(!enforcer.validate_function_call(&kinds, "search"));
  }

  #[test]
  fn test_validate_function_call_unknown_function() {
    let enforcer = CapabilityEnforcer::new();
    let kinds = vec!["metadata_extractor".to_string()];
    assert!(!enforcer.validate_function_call(&kinds, "unknown_func"));
    assert!(!enforcer.validate_function_call(&kinds, ""));
  }

  #[test]
  fn test_validate_function_call_shared_supported_types() {
    let enforcer = CapabilityEnforcer::new();
    let extractor = vec!["metadata_extractor".to_string()];
    let generator = vec!["thumbnail_generator".to_string()];
    let search = vec!["search_backend".to_string()];
    assert!(enforcer.validate_function_call(&extractor, "supported_types"));
    assert!(enforcer.validate_function_call(&generator, "supported_types"));
    assert!(!enforcer.validate_function_call(&search, "supported_types"));
  }
}