"""Opt-in daily digest — a finite, calm morning email of today's brief.

Ritual, not capture: no streaks, no "you missed", no urgency, no unread counts.
One send per opted-in user per day, gated to a morning window in the site
timezone and deduped via digest_sends. On a thin day it skips quietly rather
than padding. Reuses the existing SMTP/email pipeline.
"""

from __future__ import annotations

import os
import secrets
import sqlite3
from datetime import datetime
from html import escape

from . import email_send
from .localtime import local_now, local_today
from .paywall import is_paywalled

DIGEST_HOUR = int(os.environ.get("GOODNEWS_DIGEST_HOUR", "7"))
DIGEST_WINDOW_HOURS = 4  # send between DIGEST_HOUR and +4h, site-local
MIN_ITEMS = 4            # below this, skip the day rather than pad


def _base_url() -> str:
    return os.environ.get("GOODNEWS_PUBLIC_BASE_URL", "https://upbeatbytes.com").rstrip("/")


def digest_items(conn: sqlite3.Connection, brief_date: str, limit: int = 7) -> list[dict]:
    """The brief's items with the bits a calm email needs (visible sources only)."""
    rows = conn.execute(
        """
        SELECT a.id, a.title, a.canonical_url, s.name AS source, sc.reason_text,
               (SELECT summary FROM article_summaries WHERE article_id = a.id) AS summary
        FROM daily_briefs b
        JOIN daily_brief_items bi ON bi.brief_id = b.id
        JOIN articles a ON a.id = bi.article_id
        JOIN sources s ON s.id = a.source_id
        LEFT JOIN article_scores sc ON sc.article_id = a.id
        WHERE b.brief_date = ? AND s.content_visible = 1
        ORDER BY bi.rank
        LIMIT ?
        """,
        (brief_date, limit),
    ).fetchall()
    items = []
    for r in rows:
        d = dict(r)
        d["paywalled"] = is_paywalled(d["canonical_url"])
        items.append(d)
    return items


def _weekday(brief_date: str) -> str:
    try:
        return datetime.strptime(brief_date, "%Y-%m-%d").strftime("%A")
    except (ValueError, TypeError):
        return "today"


def build_digest(items: list[dict], brief_date: str, unsub_url: str, base: str | None = None) -> tuple[str, str, str]:
    """Return (subject, text, html) for the digest — calm and dated, no urgency."""
    base = base or _base_url()
    n = len(items)
    weekday = _weekday(brief_date)
    subject = f"{weekday}'s Upbeat Bytes · {n} calm read{'' if n == 1 else 's'}"
    if weekday == "today":
        subject = f"Today's Upbeat Bytes · {n} calm reads"

    text_lines = [f"Today's good news — {n} calm reads.\n"]
    for it in items:
        text_lines.append(f"• {it['title']}  ({it['source']})")
        if it.get("summary"):
            text_lines.append(f"  {it['summary']}")
        text_lines.append(f"  Read: {base}/a/{it['id']}")
        text_lines.append(f"  Source: {it['canonical_url']}\n")
    text_lines.append("That's today's good news. You're caught up — see you tomorrow.")
    text_lines.append(f"\nTo stop these emails: {unsub_url}")
    text = "\n".join(text_lines)

    blocks = []
    for it in items:
        summary = f'<div style="font-size:15px;line-height:1.5;color:#16263a">{escape(it["summary"])}</div>' if it.get("summary") else ""
        why = f'<div style="font-size:13px;color:#5d6b78;margin-top:6px"><em>Why it’s here:</em> {escape(it["reason_text"])}</div>' if it.get("reason_text") else ""
        lock = " \U0001f512" if it.get("paywalled") else ""
        blocks.append(
            '<div style="margin:0 0 22px;padding:0 0 18px;border-bottom:1px solid #e8e3d8">'
            f'<a href="{base}/a/{it["id"]}" style="font-size:18px;font-weight:600;color:#16263a;text-decoration:none">{escape(it["title"])}</a>'
            f'<div style="color:#5d6b78;font-size:13px;margin:3px 0 8px">{escape(it["source"])}</div>'
            f'{summary}{why}'
            '<div style="margin-top:10px;font-size:14px">'
            f'<a href="{base}/a/{it["id"]}" style="color:#0083ad;text-decoration:none">Read on Upbeat Bytes</a>'
            f' &nbsp;·&nbsp; <a href="{escape(it["canonical_url"])}" style="color:#5d6b78;text-decoration:none">Full story at source{lock}</a>'
            '</div></div>'
        )
    html = (
        '<div style="max-width:600px;margin:0 auto;padding:8px 4px;'
        'font-family:-apple-system,Segoe UI,Roboto,Helvetica,Arial,sans-serif;color:#16263a">'
        '<h1 style="font-size:22px;margin:0 0 4px">Today’s good news</h1>'
        f'<p style="color:#5d6b78;font-size:14px;margin:0 0 22px">{n} calm reads for {escape(weekday)}</p>'
        + "".join(blocks)
        + '<p style="font-size:15px;color:#3f7048;margin:8px 0 0">That’s today’s good news. '
          'You’re caught up — see you tomorrow.</p>'
        f'<p style="font-size:12px;color:#9aa6b2;margin-top:24px">You’re getting this because you turned on '
        f'the daily digest. <a href="{unsub_url}" style="color:#9aa6b2">Unsubscribe</a>.</p>'
        '</div>'
    )
    return subject, text, html


def unsub_url(user: dict, base: str | None = None) -> str:
    base = base or _base_url()
    return f"{base}/api/digest/unsubscribe?u={user['id']}&t={user['digest_unsub_token']}"


def send_due_digests(conn: sqlite3.Connection, force: bool = False, base: str | None = None) -> int:
    """Send today's digest to opted-in users who haven't received it yet.

    Gated to the morning window unless force=True (manual CLI). Skips quietly on
    a thin day. Deduped via digest_sends. Returns the number sent.
    """
    if not force:
        hour = local_now().hour
        if hour < DIGEST_HOUR or hour >= DIGEST_HOUR + DIGEST_WINDOW_HOURS:
            return 0
    brief_date = local_today()
    items = digest_items(conn, brief_date)
    if len(items) < MIN_ITEMS:
        return 0
    base = base or _base_url()

    users = conn.execute(
        """
        SELECT u.id, u.email, u.digest_unsub_token
        FROM users u
        WHERE u.digest_enabled = 1
          AND NOT EXISTS (SELECT 1 FROM digest_sends d WHERE d.user_id = u.id AND d.brief_date = ?)
        """,
        (brief_date,),
    ).fetchall()

    sent = 0
    for row in users:
        user = dict(row)
        if not user.get("digest_unsub_token"):
            token = secrets.token_urlsafe(18)
            conn.execute("UPDATE users SET digest_unsub_token = ? WHERE id = ?", (token, user["id"]))
            conn.commit()
            user["digest_unsub_token"] = token
        subject, text, html = build_digest(items, brief_date, unsub_url(user, base), base)
        try:
            email_send.send_email(user["email"], subject, text, html=html)
        except Exception:  # noqa: BLE001 — one bad send shouldn't stop the rest; retry next window
            continue
        conn.execute(
            "INSERT OR IGNORE INTO digest_sends (user_id, brief_date, item_count) VALUES (?, ?, ?)",
            (user["id"], brief_date, len(items)),
        )
        conn.commit()
        sent += 1
    return sent