use bytes::Bytes;
use codex_protocol::config_types::WindowsSandboxLevel;
use codex_protocol::models::ManagedFileSystemPermissions;
use codex_protocol::models::PermissionProfile;
use codex_protocol::models::SandboxEnforcement;
use codex_protocol::permissions::FileSystemPath;
use codex_protocol::permissions::FileSystemSandboxKind;
use codex_protocol::permissions::FileSystemSandboxPolicy;
use codex_protocol::permissions::FileSystemSpecialPath;
use codex_protocol::permissions::NetworkSandboxPolicy;
use codex_protocol::protocol::SandboxPolicy;
use codex_utils_absolute_path::AbsolutePathBuf;
use codex_utils_path_uri::PathUri;
use futures::Stream;
use std::future::Future;
use std::io;
use std::path::Path;
use std::pin::Pin;
use std::task::Context;
use std::task::Poll;

/// Maximum chunk size returned by [`ExecutorFileSystem::read_file_stream`].
pub const FILE_READ_CHUNK_SIZE: usize = 1024 * 1024;

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct CreateDirectoryOptions {
    pub recursive: bool,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct RemoveOptions {
    pub recursive: bool,
    pub force: bool,
}

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct CopyOptions {
    pub recursive: bool,
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct FileMetadata {
    pub is_directory: bool,
    pub is_file: bool,
    pub is_symlink: bool,
    /// Size in bytes.
    pub size: u64,
    pub created_at_ms: i64,
    pub modified_at_ms: i64,
}

#[derive(Clone, Debug, Eq, PartialEq)]
pub struct ReadDirectoryEntry {
    pub file_name: String,
    pub is_directory: bool,
    pub is_file: bool,
}

#[derive(Clone, Debug, Eq, PartialEq, serde::Serialize, serde::Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct FileSystemSandboxContext {
    pub permissions: PermissionProfile<PathUri>,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub cwd: Option<PathUri>,
    #[serde(default, skip_serializing_if = "Vec::is_empty")]
    pub workspace_roots: Vec<PathUri>,
    pub windows_sandbox_level: WindowsSandboxLevel,
    #[serde(default)]
    pub windows_sandbox_private_desktop: bool,
    #[serde(default)]
    pub use_legacy_landlock: bool,
}

impl FileSystemSandboxContext {
    pub fn from_legacy_sandbox_policy(
        sandbox_policy: SandboxPolicy,
        cwd: PathUri,
    ) -> io::Result<Self> {
        // Legacy policy projection materializes native roots, so convert at the receiving-host
        // boundary while retaining the URI in the resulting sandbox context.
        let native_cwd = cwd.to_abs_path()?;
        let file_system_sandbox_policy =
            FileSystemSandboxPolicy::from_legacy_sandbox_policy_for_cwd(
                &sandbox_policy,
                &native_cwd,
            );
        let permissions =
            PermissionProfile::<AbsolutePathBuf>::from_runtime_permissions_with_enforcement(
                SandboxEnforcement::from_legacy_sandbox_policy(&sandbox_policy),
                &file_system_sandbox_policy,
                NetworkSandboxPolicy::from(&sandbox_policy),
            );
        Ok(Self::from_permission_profile_with_cwd(permissions, cwd))
    }

    pub fn from_permission_profile(permissions: PermissionProfile<AbsolutePathBuf>) -> Self {
        Self::from_permissions_and_cwd(permissions, /*cwd*/ None)
    }

    pub fn from_permission_profile_with_cwd(
        permissions: PermissionProfile<AbsolutePathBuf>,
        cwd: PathUri,
    ) -> Self {
        Self::from_permissions_and_cwd(permissions, Some(cwd))
    }

    fn from_permissions_and_cwd(
        permissions: PermissionProfile<AbsolutePathBuf>,
        cwd: Option<PathUri>,
    ) -> Self {
        Self {
            permissions: permissions.into(),
            cwd,
            workspace_roots: Vec::new(),
            windows_sandbox_level: WindowsSandboxLevel::Disabled,
            windows_sandbox_private_desktop: false,
            use_legacy_landlock: false,
        }
    }

    pub fn should_run_in_sandbox(&self) -> bool {
        let Ok(permissions) =
            PermissionProfile::<AbsolutePathBuf>::try_from(self.permissions.clone())
        else {
            // A sandbox context for another host must not select the unsandboxed filesystem.
            return true;
        };
        let file_system_policy = permissions.file_system_sandbox_policy();
        matches!(file_system_policy.kind, FileSystemSandboxKind::Restricted)
            && !file_system_policy.has_full_disk_write_access()
    }

    pub fn has_cwd_dependent_permissions(&self) -> bool {
        match &self.permissions {
            PermissionProfile::Managed {
                file_system: ManagedFileSystemPermissions::Restricted { entries, .. },
                ..
            } => entries.iter().any(|entry| match &entry.path {
                FileSystemPath::GlobPattern { pattern } => !Path::new(pattern).is_absolute(),
                FileSystemPath::Special {
                    value: FileSystemSpecialPath::ProjectRoots { .. },
                } => true,
                FileSystemPath::Path { .. } | FileSystemPath::Special { .. } => false,
            }),
            PermissionProfile::Managed {
                file_system: ManagedFileSystemPermissions::Unrestricted,
                ..
            }
            | PermissionProfile::Disabled
            | PermissionProfile::External { .. } => false,
        }
    }

    pub fn drop_cwd_if_unused(mut self) -> Self {
        if !self.has_cwd_dependent_permissions() {
            self.cwd = None;
            self.workspace_roots.clear();
        }
        self
    }
}

pub type FileSystemResult<T> = io::Result<T>;

/// Future returned by [`ExecutorFileSystem`] operations.
pub type ExecutorFileSystemFuture<'a, T> =
    Pin<Box<dyn Future<Output = FileSystemResult<T>> + Send + 'a>>;

/// Stream of immutable chunks read from an [`ExecutorFileSystem`].
pub struct FileSystemReadStream {
    inner: Pin<Box<dyn Stream<Item = FileSystemResult<Bytes>> + Send + 'static>>,
}

impl FileSystemReadStream {
    /// Wraps a filesystem byte stream.
    pub fn new(stream: impl Stream<Item = FileSystemResult<Bytes>> + Send + 'static) -> Self {
        Self {
            inner: Box::pin(stream),
        }
    }
}

impl Stream for FileSystemReadStream {
    type Item = FileSystemResult<Bytes>;

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        self.inner.as_mut().poll_next(cx)
    }
}

/// Abstract filesystem access used by components that may operate locally or via
/// a remote environment.
pub trait ExecutorFileSystem: Send + Sync {
    /// Resolves a path within this filesystem.
    fn canonicalize<'a>(
        &'a self,
        path: &'a PathUri,
        sandbox: Option<&'a FileSystemSandboxContext>,
    ) -> ExecutorFileSystemFuture<'a, PathUri>;

    fn read_file<'a>(
        &'a self,
        path: &'a PathUri,
        sandbox: Option<&'a FileSystemSandboxContext>,
    ) -> ExecutorFileSystemFuture<'a, Vec<u8>>;

    /// Reads a file as a stream of chunks no larger than [`FILE_READ_CHUNK_SIZE`].
    fn read_file_stream<'a>(
        &'a self,
        path: &'a PathUri,
        sandbox: Option<&'a FileSystemSandboxContext>,
    ) -> ExecutorFileSystemFuture<'a, FileSystemReadStream>;

    /// Reads a file and decodes it as UTF-8 text.
    fn read_file_text<'a>(
        &'a self,
        path: &'a PathUri,
        sandbox: Option<&'a FileSystemSandboxContext>,
    ) -> ExecutorFileSystemFuture<'a, String> {
        Box::pin(async move {
            let bytes = self.read_file(path, sandbox).await?;
            String::from_utf8(bytes).map_err(|err| io::Error::new(io::ErrorKind::InvalidData, err))
        })
    }

    fn write_file<'a>(
        &'a self,
        path: &'a PathUri,
        contents: Vec<u8>,
        sandbox: Option<&'a FileSystemSandboxContext>,
    ) -> ExecutorFileSystemFuture<'a, ()>;

    fn create_directory<'a>(
        &'a self,
        path: &'a PathUri,
        create_directory_options: CreateDirectoryOptions,
        sandbox: Option<&'a FileSystemSandboxContext>,
    ) -> ExecutorFileSystemFuture<'a, ()>;

    fn get_metadata<'a>(
        &'a self,
        path: &'a PathUri,
        sandbox: Option<&'a FileSystemSandboxContext>,
    ) -> ExecutorFileSystemFuture<'a, FileMetadata>;

    fn read_directory<'a>(
        &'a self,
        path: &'a PathUri,
        sandbox: Option<&'a FileSystemSandboxContext>,
    ) -> ExecutorFileSystemFuture<'a, Vec<ReadDirectoryEntry>>;

    fn remove<'a>(
        &'a self,
        path: &'a PathUri,
        remove_options: RemoveOptions,
        sandbox: Option<&'a FileSystemSandboxContext>,
    ) -> ExecutorFileSystemFuture<'a, ()>;

    fn copy<'a>(
        &'a self,
        source_path: &'a PathUri,
        destination_path: &'a PathUri,
        copy_options: CopyOptions,
        sandbox: Option<&'a FileSystemSandboxContext>,
    ) -> ExecutorFileSystemFuture<'a, ()>;
}