"""File storage and workspace browsing helpers for the web API."""

from __future__ import annotations

import json
import mimetypes
import shutil
import uuid
from datetime import datetime, timezone
from pathlib import Path
from typing import Any
from urllib.parse import quote


def content_disposition(disposition: str, filename: str) -> str:
    """Build a Content-Disposition header, including RFC 5987 for non-ASCII names."""

    try:
        filename.encode("ascii")
        return f'{disposition}; filename="{filename}"'
    except UnicodeEncodeError:
        utf8_quoted = quote(filename)
        return f"{disposition}; filename*=UTF-8''{utf8_quoted}"


def generate_file_id() -> str:
    """Generate a short unique file id."""

    return uuid.uuid4().hex[:12]


def save_file(
    workspace: Path,
    file_id: str,
    filename: str,
    content: bytes,
    content_type: str,
    session_id: str = "web:default",
) -> dict[str, Any]:
    """Save an uploaded attachment under workspace/files/<file_id>/."""

    if not _is_safe_filename(filename):
        raise ValueError(f"Invalid filename: {filename}")

    file_dir = _files_dir(workspace) / file_id
    file_dir.mkdir(parents=True, exist_ok=True)
    file_path = file_dir / filename
    file_path.write_bytes(content)

    metadata = {
        "file_id": file_id,
        "name": filename,
        "content_type": content_type,
        "size": len(content),
        "created_at": datetime.now(timezone.utc).isoformat(),
        "session_id": session_id,
    }
    (file_dir / "metadata.json").write_text(json.dumps(metadata, ensure_ascii=False), encoding="utf-8")
    return metadata


def get_file_metadata(workspace: Path, file_id: str) -> dict[str, Any] | None:
    """Load attachment metadata."""

    if not _is_safe_file_id(file_id):
        return None

    meta_path = _files_dir(workspace) / file_id / "metadata.json"
    if not meta_path.exists():
        return None

    try:
        data = json.loads(meta_path.read_text(encoding="utf-8"))
    except (json.JSONDecodeError, ValueError):
        return None
    return data if isinstance(data, dict) else None


def get_file_path(workspace: Path, file_id: str) -> Path | None:
    """Resolve the stored attachment path."""

    meta = get_file_metadata(workspace, file_id)
    if meta is None:
        return None

    file_path = _files_dir(workspace) / file_id / str(meta.get("name") or "")
    try:
        file_path.resolve().relative_to(_files_dir(workspace).resolve())
    except ValueError:
        return None
    return file_path if file_path.exists() and file_path.is_file() else None


def list_files(workspace: Path, session_id: str | None = None) -> list[dict[str, Any]]:
    """List uploaded attachments, optionally filtered by session."""

    files_dir = _files_dir(workspace)
    result: list[dict[str, Any]] = []
    for entry in sorted(files_dir.iterdir()):
        if not entry.is_dir():
            continue
        meta_path = entry / "metadata.json"
        if not meta_path.exists():
            continue
        try:
            meta = json.loads(meta_path.read_text(encoding="utf-8"))
        except (json.JSONDecodeError, ValueError):
            continue
        if not isinstance(meta, dict):
            continue
        if session_id and meta.get("session_id") != session_id:
            continue
        result.append(meta)
    return result


def delete_file(workspace: Path, file_id: str) -> bool:
    """Delete a stored attachment by id."""

    if not _is_safe_file_id(file_id):
        return False

    file_dir = _files_dir(workspace) / file_id
    if not file_dir.exists():
        return False
    shutil.rmtree(file_dir)
    return True


def browse_workspace(workspace: Path, rel_path: str = "") -> dict[str, Any]:
    """List files and directories below the workspace root."""

    workspace = _ensure_workspace(workspace)
    target = _resolve_workspace_path(workspace, rel_path)
    if target is None or not target.is_dir():
        raise ValueError("Invalid directory path")

    try:
        entries = sorted(target.iterdir(), key=lambda entry: (not entry.is_dir(), entry.name.lower()))
    except PermissionError as exc:
        raise ValueError("Permission denied") from exc

    items: list[dict[str, Any]] = []
    for entry in entries:
        if entry.name.startswith("."):
            continue
        rel = str(entry.relative_to(workspace))
        if entry.is_dir():
            items.append(
                {
                    "name": entry.name,
                    "path": rel,
                    "type": "directory",
                    "size": None,
                    "modified": datetime.fromtimestamp(entry.stat().st_mtime, tz=timezone.utc).isoformat(),
                }
            )
        elif entry.is_file():
            stat = entry.stat()
            content_type, _ = mimetypes.guess_type(entry.name)
            items.append(
                {
                    "name": entry.name,
                    "path": rel,
                    "type": "file",
                    "size": stat.st_size,
                    "content_type": content_type or "application/octet-stream",
                    "modified": datetime.fromtimestamp(stat.st_mtime, tz=timezone.utc).isoformat(),
                }
            )

    return {
        "path": str(target.relative_to(workspace)) if target != workspace else "",
        "items": items,
    }


def workspace_file_path(workspace: Path, rel_path: str) -> Path | None:
    """Resolve a workspace file path for download."""

    workspace = _ensure_workspace(workspace)
    target = _resolve_workspace_path(workspace, rel_path)
    if target is None or not target.is_file():
        return None
    return target


def workspace_file_preview(workspace: Path, rel_path: str, *, max_bytes: int = 1024 * 1024) -> dict[str, Any]:
    """Return a bounded preview payload for a workspace file."""

    file_path = workspace_file_path(workspace, rel_path)
    if file_path is None:
        raise ValueError("File not found")

    stat = file_path.stat()
    content_type, _ = mimetypes.guess_type(file_path.name)
    content_type = content_type or "application/octet-stream"
    raw = file_path.read_bytes() if stat.st_size <= max_bytes else file_path.read_bytes()[:max_bytes]
    is_binary = _is_probably_binary(raw, content_type)
    content = None if is_binary else raw.decode("utf-8", errors="replace")
    return {
        "name": file_path.name,
        "path": str(file_path.relative_to(_ensure_workspace(workspace))),
        "size": stat.st_size,
        "content_type": content_type,
        "modified": datetime.fromtimestamp(stat.st_mtime, tz=timezone.utc).isoformat(),
        "is_binary": is_binary,
        "is_truncated": stat.st_size > max_bytes,
        "content": content,
    }


def save_to_workspace(workspace: Path, rel_dir: str, filename: str, content: bytes) -> dict[str, Any]:
    """Save an uploaded file to a workspace directory."""

    if not filename:
        raise ValueError("Invalid filename")

    workspace = _ensure_workspace(workspace)
    target_dir = _resolve_workspace_path(workspace, rel_dir)
    if target_dir is None:
        raise ValueError("Invalid directory path")
    target_dir.mkdir(parents=True, exist_ok=True)

    file_path = (target_dir / filename).resolve()
    try:
        file_path.relative_to(workspace)
    except ValueError as exc:
        raise ValueError("Invalid filename") from exc

    file_path.write_bytes(content)
    stat = file_path.stat()
    content_type, _ = mimetypes.guess_type(filename)
    return {
        "name": filename,
        "path": str(file_path.relative_to(workspace)),
        "type": "file",
        "size": stat.st_size,
        "content_type": content_type or "application/octet-stream",
        "modified": datetime.fromtimestamp(stat.st_mtime, tz=timezone.utc).isoformat(),
    }


def delete_workspace_path(workspace: Path, rel_path: str) -> bool:
    """Delete a file or directory below workspace root."""

    workspace = _ensure_workspace(workspace)
    target = _resolve_workspace_path(workspace, rel_path)
    if target is None or not target.exists() or target == workspace:
        return False
    if target.is_dir():
        shutil.rmtree(target)
    else:
        target.unlink()
    return True


def create_workspace_dir(workspace: Path, rel_path: str) -> dict[str, Any]:
    """Create a directory below workspace root."""

    workspace = _ensure_workspace(workspace)
    target = _resolve_workspace_path(workspace, rel_path)
    if target is None or target == workspace:
        raise ValueError("Invalid directory path")
    target.mkdir(parents=True, exist_ok=True)
    stat = target.stat()
    return {
        "name": target.name,
        "path": str(target.relative_to(workspace)),
        "type": "directory",
        "size": None,
        "modified": datetime.fromtimestamp(stat.st_mtime, tz=timezone.utc).isoformat(),
    }


def _files_dir(workspace: Path) -> Path:
    directory = _ensure_workspace(workspace) / "files"
    directory.mkdir(parents=True, exist_ok=True)
    return directory


def _ensure_workspace(workspace: Path) -> Path:
    root = Path(workspace).expanduser()
    root.mkdir(parents=True, exist_ok=True)
    return root.resolve()


def _resolve_workspace_path(workspace: Path, rel_path: str) -> Path | None:
    root = _ensure_workspace(workspace)
    target = (root / rel_path).resolve()
    try:
        target.relative_to(root)
    except ValueError:
        return None
    return target


def _is_probably_binary(raw: bytes, content_type: str) -> bool:
    if content_type.startswith("text/") or content_type in {
        "application/json",
        "application/javascript",
        "application/xml",
        "application/x-yaml",
    }:
        return False
    if not raw:
        return False
    if b"\x00" in raw[:4096]:
        return True
    try:
        raw[:4096].decode("utf-8")
    except UnicodeDecodeError:
        return True
    return False


def _is_safe_filename(filename: str) -> bool:
    return bool(filename) and "/" not in filename and "\\" not in filename and not filename.startswith(".")


def _is_safe_file_id(file_id: str) -> bool:
    return bool(file_id) and all(char in "0123456789abcdef" for char in file_id)