"""
Public routes for StarPunk

Handles public-facing pages including homepage and note permalinks.
No authentication required for these routes.
"""

import hashlib
from datetime import datetime, timedelta

from flask import Blueprint, abort, render_template, Response, current_app, request

from starpunk.notes import list_notes, get_note
from starpunk.feed import generate_feed_streaming  # Legacy RSS
from starpunk.feeds import (
    generate_rss_streaming,
    generate_atom_streaming,
    generate_json_feed_streaming,
    negotiate_feed_format,
    get_mime_type,
)

# Create blueprint
bp = Blueprint("public", __name__)

# Simple in-memory cache for feed note list
# Caches the database query results to avoid repeated DB hits
# Feed content (XML/JSON) is streamed, not cached (memory optimization)
# Structure: {'notes': list[Note], 'timestamp': datetime}
_feed_cache = {"notes": None, "timestamp": None}


def _get_cached_notes():
    """
    Get cached note list or fetch fresh notes

    Returns cached notes if still valid, otherwise fetches fresh notes
    from database and updates cache.

    Returns:
        List of published notes for feed generation
    """
    # Get cache duration from config (in seconds)
    cache_seconds = current_app.config.get("FEED_CACHE_SECONDS", 300)
    cache_duration = timedelta(seconds=cache_seconds)
    now = datetime.utcnow()

    # Check if note list cache is valid
    if _feed_cache["notes"] and _feed_cache["timestamp"]:
        cache_age = now - _feed_cache["timestamp"]
        if cache_age < cache_duration:
            # Use cached note list
            return _feed_cache["notes"]

    # Cache expired or empty, fetch fresh notes
    max_items = current_app.config.get("FEED_MAX_ITEMS", 50)
    notes = list_notes(published_only=True, limit=max_items)
    _feed_cache["notes"] = notes
    _feed_cache["timestamp"] = now

    return notes


@bp.route("/")
def index():
    """
    Homepage displaying recent published notes

    Returns:
        Rendered homepage template with note list

    Template: templates/index.html
    Microformats: h-feed containing h-entry items
    """
    # Get recent published notes (limit 20)
    notes = list_notes(published_only=True, limit=20)

    return render_template("index.html", notes=notes)


@bp.route("/note/<slug>")
def note(slug: str):
    """
    Individual note permalink page

    Args:
        slug: URL-safe note identifier

    Returns:
        Rendered note template with full content

    Raises:
        404: If note not found or not published

    Template: templates/note.html
    Microformats: h-entry
    """
    # Get note by slug
    note_obj = get_note(slug=slug)

    # Return 404 if note doesn't exist or isn't published
    if not note_obj or not note_obj.published:
        abort(404)

    return render_template("note.html", note=note_obj)


@bp.route("/feed")
def feed():
    """
    Content negotiation endpoint for feeds

    Serves feed in format based on HTTP Accept header:
    - application/rss+xml → RSS 2.0
    - application/atom+xml → ATOM 1.0
    - application/feed+json or application/json → JSON Feed 1.1
    - */* → RSS 2.0 (default)

    If no acceptable format is available, returns 406 Not Acceptable with
    X-Available-Formats header listing supported formats.

    Returns:
        Streaming feed response in negotiated format, or 406 error

    Headers:
        Content-Type: Varies by format
        Cache-Control: public, max-age={FEED_CACHE_SECONDS}
        X-Available-Formats: List of supported formats (on 406 error only)

    Examples:
        >>> # Request with Accept: application/atom+xml
        >>> response = client.get('/feed', headers={'Accept': 'application/atom+xml'})
        >>> response.headers['Content-Type']
        'application/atom+xml; charset=utf-8'

        >>> # Request with no Accept header (defaults to RSS)
        >>> response = client.get('/feed')
        >>> response.headers['Content-Type']
        'application/rss+xml; charset=utf-8'
    """
    # Get Accept header
    accept = request.headers.get('Accept', '*/*')

    # Negotiate format
    available_formats = ['rss', 'atom', 'json']
    try:
        format_name = negotiate_feed_format(accept, available_formats)
    except ValueError:
        # No acceptable format - return 406
        return (
            "Not Acceptable. Supported formats: application/rss+xml, application/atom+xml, application/feed+json",
            406,
            {
                'Content-Type': 'text/plain; charset=utf-8',
                'X-Available-Formats': 'application/rss+xml, application/atom+xml, application/feed+json',
            }
        )

    # Route to appropriate generator
    if format_name == 'rss':
        return feed_rss()
    elif format_name == 'atom':
        return feed_atom()
    elif format_name == 'json':
        return feed_json()
    else:
        # Shouldn't reach here, but be defensive
        return feed_rss()


@bp.route("/feed.rss")
def feed_rss():
    """
    Explicit RSS 2.0 feed endpoint

    Generates standards-compliant RSS 2.0 feed using memory-efficient streaming.
    Instead of building the entire feed in memory, yields XML chunks directly
    to the client for optimal memory usage with large feeds.

    Cache duration is configurable via FEED_CACHE_SECONDS (default: 300 seconds
    = 5 minutes). Cache stores note list to avoid repeated database queries,
    but streaming prevents holding full XML in memory.

    Returns:
        Streaming RSS 2.0 feed response

    Headers:
        Content-Type: application/rss+xml; charset=utf-8
        Cache-Control: public, max-age={FEED_CACHE_SECONDS}

    Streaming Strategy:
        - Database query cached (avoid repeated DB hits)
        - XML generation streamed (avoid full XML in memory)
        - Client-side: Cache-Control header with max-age

    Performance:
        - Memory usage: O(1) instead of O(n) for feed size
        - Latency: Lower time-to-first-byte (TTFB)
        - Recommended for feeds with 100+ items

    Examples:
        >>> response = client.get('/feed.rss')
        >>> response.status_code
        200
        >>> response.headers['Content-Type']
        'application/rss+xml; charset=utf-8'
    """
    # Get cached notes
    notes = _get_cached_notes()

    # Get cache duration for response header
    cache_seconds = current_app.config.get("FEED_CACHE_SECONDS", 300)

    # Generate streaming RSS feed
    max_items = current_app.config.get("FEED_MAX_ITEMS", 50)
    generator = generate_rss_streaming(
        site_url=current_app.config["SITE_URL"],
        site_name=current_app.config["SITE_NAME"],
        site_description=current_app.config.get("SITE_DESCRIPTION", ""),
        notes=notes,
        limit=max_items,
    )

    # Return streaming response with appropriate headers
    response = Response(generator, mimetype="application/rss+xml; charset=utf-8")
    response.headers["Cache-Control"] = f"public, max-age={cache_seconds}"

    return response


@bp.route("/feed.atom")
def feed_atom():
    """
    Explicit ATOM 1.0 feed endpoint

    Generates standards-compliant ATOM 1.0 feed using memory-efficient streaming.
    Follows RFC 4287 specification for ATOM syndication format.

    Returns:
        Streaming ATOM 1.0 feed response

    Headers:
        Content-Type: application/atom+xml; charset=utf-8
        Cache-Control: public, max-age={FEED_CACHE_SECONDS}

    Examples:
        >>> response = client.get('/feed.atom')
        >>> response.status_code
        200
        >>> response.headers['Content-Type']
        'application/atom+xml; charset=utf-8'
    """
    # Get cached notes
    notes = _get_cached_notes()

    # Get cache duration for response header
    cache_seconds = current_app.config.get("FEED_CACHE_SECONDS", 300)

    # Generate streaming ATOM feed
    max_items = current_app.config.get("FEED_MAX_ITEMS", 50)
    generator = generate_atom_streaming(
        site_url=current_app.config["SITE_URL"],
        site_name=current_app.config["SITE_NAME"],
        site_description=current_app.config.get("SITE_DESCRIPTION", ""),
        notes=notes,
        limit=max_items,
    )

    # Return streaming response with appropriate headers
    response = Response(generator, mimetype="application/atom+xml; charset=utf-8")
    response.headers["Cache-Control"] = f"public, max-age={cache_seconds}"

    return response


@bp.route("/feed.json")
def feed_json():
    """
    Explicit JSON Feed 1.1 endpoint

    Generates standards-compliant JSON Feed 1.1 feed using memory-efficient streaming.
    Follows JSON Feed specification (https://jsonfeed.org/version/1.1).

    Returns:
        Streaming JSON Feed 1.1 response

    Headers:
        Content-Type: application/feed+json; charset=utf-8
        Cache-Control: public, max-age={FEED_CACHE_SECONDS}

    Examples:
        >>> response = client.get('/feed.json')
        >>> response.status_code
        200
        >>> response.headers['Content-Type']
        'application/feed+json; charset=utf-8'
    """
    # Get cached notes
    notes = _get_cached_notes()

    # Get cache duration for response header
    cache_seconds = current_app.config.get("FEED_CACHE_SECONDS", 300)

    # Generate streaming JSON Feed
    max_items = current_app.config.get("FEED_MAX_ITEMS", 50)
    generator = generate_json_feed_streaming(
        site_url=current_app.config["SITE_URL"],
        site_name=current_app.config["SITE_NAME"],
        site_description=current_app.config.get("SITE_DESCRIPTION", ""),
        notes=notes,
        limit=max_items,
    )

    # Return streaming response with appropriate headers
    response = Response(generator, mimetype="application/feed+json; charset=utf-8")
    response.headers["Cache-Control"] = f"public, max-age={cache_seconds}"

    return response


@bp.route("/feed.xml")
def feed_xml_legacy():
    """
    Legacy RSS 2.0 feed endpoint (backward compatibility)

    Maintains backward compatibility for /feed.xml endpoint.
    New code should use /feed.rss or /feed with content negotiation.

    Returns:
        Streaming RSS 2.0 feed response

    See feed_rss() for full documentation.
    """
    # Use the new RSS endpoint
    return feed_rss()