"""
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

from starpunk.notes import list_notes, get_note
from starpunk.feed import generate_feed_streaming

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

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


@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.xml")
def feed():
    """
    RSS 2.0 feed of published notes

    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 XML response with RSS feed

    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:
        >>> # Request streams XML directly to client
        >>> response = client.get('/feed.xml')
        >>> response.status_code
        200
        >>> response.headers['Content-Type']
        'application/rss+xml; charset=utf-8'
    """
    # 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
    # We cache the note list to avoid repeated DB queries, but still stream the XML
    if _feed_cache["notes"] and _feed_cache["timestamp"]:
        cache_age = now - _feed_cache["timestamp"]
        if cache_age < cache_duration:
            # Use cached note list
            notes = _feed_cache["notes"]
        else:
            # Cache expired, 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
    else:
        # No cache, fetch 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

    # Generate streaming response
    # This avoids holding the full XML in memory - chunks are yielded directly
    max_items = current_app.config.get("FEED_MAX_ITEMS", 50)
    generator = generate_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/rss+xml; charset=utf-8")
    response.headers["Cache-Control"] = f"public, max-age={cache_seconds}"

    return response