from __future__ import annotations

import json
import os
import re
from pathlib import Path
from typing import Any
from urllib.error import HTTPError, URLError
from urllib.parse import urlencode
from urllib.request import Request, urlopen

DEFAULT_MAX_RESULTS = 20
DEFAULT_TIMEOUT_SEC = 30

# ---------------------------------------------------------------------------
# Endpoint allowlist (regex patterns)
# Only endpoints matching these patterns are permitted.
# ---------------------------------------------------------------------------
ALLOWED_ENDPOINT_PATTERNS: list[str] = [
    # User data
    r"^/whoami-v2$",
    r"^/users/[^/]+/overview$",
    r"^/users/[^/]+/likes$",
    r"^/users/[^/]+/followers$",
    r"^/users/[^/]+/following$",
    # Organizations
    r"^/organizations/[^/]+/overview$",
    r"^/organizations/[^/]+/members$",
    r"^/organizations/[^/]+/followers$",
    # Discussions & PRs (repo_type: models, datasets, spaces)
    r"^/(models|datasets|spaces)/[^/]+/[^/]+/discussions$",
    r"^/(models|datasets|spaces)/[^/]+/[^/]+/discussions/\d+$",
    r"^/(models|datasets|spaces)/[^/]+/[^/]+/discussions/\d+/comment$",
    r"^/(models|datasets|spaces)/[^/]+/[^/]+/discussions/\d+/comment/[^/]+/edit$",
    r"^/(models|datasets|spaces)/[^/]+/[^/]+/discussions/\d+/comment/[^/]+/hide$",
    r"^/(models|datasets|spaces)/[^/]+/[^/]+/discussions/\d+/status$",
    # Access requests (gated repos)
    r"^/(models|datasets|spaces)/[^/]+/[^/]+/user-access-request/pending$",
    r"^/(models|datasets|spaces)/[^/]+/[^/]+/user-access-request/accepted$",
    r"^/(models|datasets|spaces)/[^/]+/[^/]+/user-access-request/rejected$",
    r"^/(models|datasets|spaces)/[^/]+/[^/]+/user-access-request/handle$",
    r"^/(models|datasets|spaces)/[^/]+/[^/]+/user-access-request/grant$",
    # Collections
    r"^/collections$",
    r"^/collections/[^/]+$",
    r"^/collections/[^/]+/items$",
    # Auth check
    r"^/(models|datasets|spaces)/[^/]+/[^/]+/auth-check$",
    # Recent activity feed (undocumented)
    r"^/recent-activity$",
]

_COMPILED_PATTERNS: list[re.Pattern[str]] = [
    re.compile(p) for p in ALLOWED_ENDPOINT_PATTERNS
]


def _is_endpoint_allowed(endpoint: str) -> bool:
    """Return True if endpoint matches any allowed pattern."""
    return any(pattern.match(endpoint) for pattern in _COMPILED_PATTERNS)


def _load_token() -> str | None:
    # Check for request-scoped token first (when running as MCP server)
    # This allows clients to pass their own HF token via Authorization header
    try:
        from fast_agent.mcp.auth.context import request_bearer_token

        ctx_token = request_bearer_token.get()
        if ctx_token:
            return ctx_token
    except ImportError:
        # fast_agent.mcp.auth.context not available
        pass

    # Fall back to HF_TOKEN environment variable
    token = os.getenv("HF_TOKEN")
    if token:
        return token

    # Fall back to cached huggingface token file
    token_path = Path.home() / ".cache" / "huggingface" / "token"
    if token_path.exists():
        token_value = token_path.read_text(encoding="utf-8").strip()
        return token_value or None

    return None


def _max_results_from_env() -> int:
    raw = os.getenv("HF_MAX_RESULTS")
    if not raw:
        return DEFAULT_MAX_RESULTS
    try:
        value = int(raw)
    except ValueError:
        return DEFAULT_MAX_RESULTS
    return value if value > 0 else DEFAULT_MAX_RESULTS


def _normalize_endpoint(endpoint: str) -> str:
    """Normalize and validate an endpoint path.

    Checks:
    - Must be a relative path (not a full URL)
    - Must be non-empty
    - No path traversal sequences (..)
    - Must match the endpoint allowlist
    """
    if endpoint.startswith("http://") or endpoint.startswith("https://"):
        raise ValueError("Endpoint must be a path relative to /api, not a full URL.")
    endpoint = endpoint.strip()
    if not endpoint:
        raise ValueError("Endpoint must be a non-empty string.")

    # Path traversal protection
    if ".." in endpoint:
        raise ValueError("Path traversal sequences (..) are not allowed in endpoints.")

    if not endpoint.startswith("/"):
        endpoint = f"/{endpoint}"

    # Allowlist validation
    if not _is_endpoint_allowed(endpoint):
        raise ValueError(
            f"Endpoint '{endpoint}' is not in the allowed list. "
            "See ALLOWED_ENDPOINT_PATTERNS for permitted endpoints."
        )

    return endpoint


def _normalize_params(params: dict[str, Any] | None) -> dict[str, Any]:
    if not params:
        return {}
    normalized: dict[str, Any] = {}
    for key, value in params.items():
        if value is None:
            continue
        if isinstance(value, (list, tuple)):
            normalized[key] = [str(item) for item in value]
        else:
            normalized[key] = str(value)
    return normalized


def _build_url(endpoint: str, params: dict[str, Any] | None) -> str:
    base = os.getenv("HF_ENDPOINT", "https://huggingface.co").rstrip("/")
    url = f"{base}/api{_normalize_endpoint(endpoint)}"
    normalized_params = _normalize_params(params)
    if normalized_params:
        url = f"{url}?{urlencode(normalized_params, doseq=True)}"
    return url


def _request_once(
    *,
    url: str,
    method_upper: str,
    json_body: dict[str, Any] | None,
) -> tuple[int, Any]:
    headers = {"Accept": "application/json"}
    token = _load_token()
    if token:
        headers["Authorization"] = f"Bearer {token}"

    data = None
    if method_upper == "POST":
        headers["Content-Type"] = "application/json"
        data = json.dumps(json_body or {}).encode("utf-8")

    request = Request(url, headers=headers, data=data, method=method_upper)

    try:
        with urlopen(request, timeout=DEFAULT_TIMEOUT_SEC) as response:
            raw = response.read()
            status_code = response.status
    except HTTPError as exc:
        error_body = exc.read().decode("utf-8", errors="replace")
        raise RuntimeError(f"HF API error {exc.code} for {url}: {error_body}") from exc
    except URLError as exc:
        raise RuntimeError(f"HF API request failed for {url}: {exc}") from exc

    try:
        payload = json.loads(raw)
    except json.JSONDecodeError:
        payload = raw.decode("utf-8", errors="replace")

    return status_code, payload


def _get_nested_value(obj: Any, path: str) -> Any:
    cur = obj
    for part in [p for p in path.split(".") if p]:
        if isinstance(cur, dict):
            if part not in cur:
                return None
            cur = cur[part]
        elif isinstance(cur, list):
            try:
                idx = int(part)
            except ValueError:
                return None
            if idx < 0 or idx >= len(cur):
                return None
            cur = cur[idx]
        else:
            return None
    return cur


def _set_nested_value(obj: Any, path: str, value: Any) -> Any:
    if not path:
        return value
    if not isinstance(obj, dict):
        return obj

    parts = [p for p in path.split(".") if p]
    if not parts:
        return obj

    cur: Any = obj
    for part in parts[:-1]:
        if not isinstance(cur, dict):
            return obj
        nxt = cur.get(part)
        if not isinstance(nxt, dict):
            nxt = {}
            cur[part] = nxt
        cur = nxt

    if isinstance(cur, dict):
        cur[parts[-1]] = value
    return obj


def _apply_local_refine(
    payload: Any,
    *,
    data_path: str | None,
    contains: str | None,
    where: dict[str, Any] | None,
    fields: list[str] | None,
    sort_by: str | None,
    sort_desc: bool,
    max_items: int | None,
    offset: int,
) -> tuple[Any, dict[str, Any]]:
    # Decide which list to refine
    root_mode = "other"
    target_path = data_path

    if isinstance(payload, list):
        list_data = payload
        root_mode = "list"
    elif isinstance(payload, dict):
        if target_path:
            maybe_list = _get_nested_value(payload, target_path)
            list_data = maybe_list if isinstance(maybe_list, list) else None
        elif isinstance(payload.get("recentActivity"), list):
            target_path = "recentActivity"
            list_data = payload.get("recentActivity")
        else:
            list_data = None
        root_mode = "dict"
    else:
        return payload, {"refined": False, "reason": "non-json-or-scalar"}

    if list_data is None:
        return payload, {"refined": False, "reason": "no-list-target"}

    original_count = len(list_data)
    items = list_data

    if where:
        def _matches_where(item: Any) -> bool:
            if not isinstance(item, dict):
                return False
            for key, expected in where.items():
                actual = _get_nested_value(item, key)
                if actual != expected:
                    return False
            return True

        items = [item for item in items if _matches_where(item)]

    if contains:
        needle = contains.lower()
        items = [
            item
            for item in items
            if needle in json.dumps(item, ensure_ascii=False).lower()
        ]

    if sort_by:
        def _sort_key(item: Any) -> Any:
            value = _get_nested_value(item, sort_by) if isinstance(item, dict) else None
            return (value is None, value)

        items = sorted(items, key=_sort_key, reverse=sort_desc)

    if fields:
        projected: list[dict[str, Any]] = []
        for item in items:
            if not isinstance(item, dict):
                continue
            row: dict[str, Any] = {}
            for field in fields:
                row[field] = _get_nested_value(item, field)
            projected.append(row)
        items = projected

    start = max(offset, 0)
    if max_items is not None:
        end = start + max(max_items, 0)
        items = items[start:end]
    elif start:
        items = items[start:]

    if root_mode == "list":
        refined_payload: Any = items
        effective_path = "<root>"
    else:
        effective_path = target_path or "recentActivity"
        refined_payload = dict(payload)
        _set_nested_value(refined_payload, effective_path, items)

    refine_meta = {
        "refined": True,
        "data_path": effective_path,
        "original_count": original_count,
        "returned_count": len(items),
    }
    return refined_payload, refine_meta


def hf_api_request(
    endpoint: str,
    method: str = "GET",
    params: dict[str, Any] | None = None,
    json_body: dict[str, Any] | None = None,
    max_results: int | None = None,
    offset: int | None = None,
    auto_paginate: bool | None = False,
    max_pages: int | None = 1,
    data_path: str | None = None,
    contains: str | None = None,
    where: dict[str, Any] | None = None,
    fields: list[str] | None = None,
    sort_by: str | None = None,
    sort_desc: bool | None = False,
    max_items: int | None = None,
) -> dict[str, Any]:
    """
Primary Hub community API tool (GET/POST only).

When to use:
- User/org intelligence: /users/*, /organizations/*
- Collaboration flows: /{repo_type}s/{repo_id}/discussions and discussion details
- Gated access workflows: user-access-request endpoints
- Collections list/get/create/add-item
- Recent activity feed via /recent-activity

When NOT to use:
- Model/dataset semantic search/ranking
- PATCH/DELETE operations (unsupported)

Intent-to-parameter guidance:
- "latest" or "recent": add params limit and sort_by time if needed
- "top N": use max_items or max_results
- "mentioning X": use contains
- "only fields A/B": use fields projection
- Cursor feeds: use auto_paginate=True with max_pages guard

Args:
    endpoint: Endpoint path relative to /api (allowlisted).
    method: GET or POST only.
    params: Query parameters.
    json_body: JSON body for POST.
    max_results: Client-side list cap.
    offset: Client-side list offset.
    auto_paginate: Follow cursor-based pages for GET responses.
    max_pages: Max pages when auto_paginate=True.
    data_path: Dot path to target list (e.g. recentActivity).
    contains: Case-insensitive text match on serialized items.
    where: Exact-match dict using dot notation keys.
    fields: Return only selected fields (dot notation supported).
    sort_by: Dot-notation sort key.
    sort_desc: Descending sort flag.
    max_items: Post-filter cap for returned list.

Returns:
    A dict containing request URL, HTTP status, response data, and refine/pagination metadata.
    """
    method_upper = method.upper()

    # Tolerate explicit nulls from LLM/tool-calling wrappers
    auto_paginate = bool(auto_paginate) if auto_paginate is not None else False
    sort_desc = bool(sort_desc) if sort_desc is not None else False
    if max_pages is None:
        max_pages = 1
    if method_upper not in {"GET", "POST"}:
        raise ValueError("Only GET and POST are allowed for hf_api_request.")

    if method_upper == "GET" and json_body is not None:
        raise ValueError("GET requests do not accept json_body.")

    if auto_paginate and method_upper != "GET":
        raise ValueError("auto_paginate is only supported for GET requests.")

    if max_pages < 1:
        raise ValueError("max_pages must be >= 1.")

    req_params = dict(params or {})
    url = _build_url(endpoint, req_params)
    status_code, payload = _request_once(
        url=url,
        method_upper=method_upper,
        json_body=json_body,
    )

    pages_fetched = 1

    # Cursor pagination path (e.g. /recent-activity)
    if auto_paginate and isinstance(payload, dict):
        list_key: str | None = None
        if data_path:
            maybe_list = _get_nested_value(payload, data_path)
            if isinstance(maybe_list, list):
                list_key = data_path
        elif isinstance(payload.get("recentActivity"), list):
            list_key = "recentActivity"

        cursor = payload.get("cursor")
        while list_key and cursor and pages_fetched < max_pages:
            req_params["cursor"] = cursor
            page_url = _build_url(endpoint, req_params)
            _, next_payload = _request_once(
                url=page_url,
                method_upper="GET",
                json_body=None,
            )

            if not isinstance(next_payload, dict):
                break

            current_items = _get_nested_value(payload, list_key)
            next_items = _get_nested_value(next_payload, list_key)
            if not isinstance(current_items, list) or not isinstance(next_items, list):
                break

            _set_nested_value(payload, list_key, current_items + next_items)
            cursor = next_payload.get("cursor")
            payload["cursor"] = cursor
            pages_fetched += 1

    # Legacy list slicing path
    if isinstance(payload, list):
        limit = max_results if max_results is not None else _max_results_from_env()
        start = max(offset or 0, 0)
        end = start + max(limit, 0)
        payload = payload[start:end]

    # Local refine path
    refine_requested = any(
        [
            data_path is not None,
            contains is not None,
            where is not None,
            fields is not None,
            sort_by is not None,
            max_items is not None,
        ]
    )

    refine_meta: dict[str, Any] | None = None
    if refine_requested:
        payload, refine_meta = _apply_local_refine(
            payload,
            data_path=data_path,
            contains=contains,
            where=where,
            fields=fields,
            sort_by=sort_by,
            sort_desc=sort_desc,
            max_items=max_items,
            offset=max(offset or 0, 0),
        )

    result = {
        "url": url,
        "status": status_code,
        "data": payload,
        "pages_fetched": pages_fetched,
    }
    if refine_meta is not None:
        result["refine"] = refine_meta
    return result