"""
Briefing pipeline: parallel data gather + two-lane LLM synthesis.

Slot names: 'compilation' (4am), 'morning' (8am), 'midday' (12pm), 'afternoon' (4pm)
"""

import asyncio
import hashlib
import logging
from datetime import date, datetime, timezone

import httpx

from fabledassistant.models import async_session

from fabledassistant.config import Config
from fabledassistant.services.settings import get_setting

logger = logging.getLogger(__name__)

SLOT_NAMES = ("compilation", "morning", "midday", "afternoon")


def slot_greeting(slot: str) -> str:
    return {
        "compilation": "Good morning",
        "morning": "Good morning — you're at the office",
        "midday": "Midday check-in",
        "afternoon": "End of day wrap-up",
    }.get(slot, "Update")


def format_task(task: dict) -> str:
    parts = [task.get("title", "Untitled")]
    if task.get("status"):
        parts.append(f"[{task['status'].replace('_', ' ').title()}]")
    if task.get("due_date"):
        parts.append(f"due {task['due_date']}")
    if task.get("priority") and task["priority"] not in ("none", ""):
        parts.append(f"priority: {task['priority']}")
    return " — ".join(parts)


def compute_task_hash(task: dict) -> str:
    """Stable SHA-256 of the task's key change-detectable fields."""
    key = "|".join([
        str(task.get("status") or ""),
        str(task.get("priority") or ""),
        str(task.get("due_date") or ""),
        str(task.get("title") or ""),
    ])
    return hashlib.sha256(key.encode()).hexdigest()


async def split_changed_tasks(
    user_id: int,
    tasks: list[dict],
) -> tuple[list[dict], int]:
    """
    Compare tasks against the briefing_task_snapshot table.
    Returns (changed_tasks, unchanged_count).
    changed_tasks includes new tasks (no snapshot row) and tasks whose hash differs.
    """
    from sqlalchemy import text

    if not tasks:
        return [], 0

    task_ids = [t["task_id"] for t in tasks if t.get("task_id")]

    async with async_session() as session:
        result = await session.execute(
            text("""
                SELECT task_id, snapshot_hash
                FROM briefing_task_snapshot
                WHERE user_id = :uid AND task_id = ANY(:ids)
            """).bindparams(uid=user_id, ids=task_ids)
        )
        snapshots = {row.task_id: row.snapshot_hash for row in result}

    changed = []
    unchanged_count = 0
    for task in tasks:
        current_hash = compute_task_hash(task)
        stored_hash = snapshots.get(task.get("task_id"))
        if stored_hash is None or stored_hash != current_hash:
            changed.append(task)
        else:
            unchanged_count += 1

    return changed, unchanged_count


async def upsert_task_snapshots(user_id: int, tasks: list[dict]) -> None:
    """Upsert snapshot hashes for all tasks included in this briefing."""
    from sqlalchemy import text

    if not tasks:
        return

    now = datetime.now(timezone.utc)
    async with async_session() as session:
        for task in tasks:
            task_id = task.get("task_id")
            if not task_id:
                continue
            await session.execute(
                text("""
                    INSERT INTO briefing_task_snapshot (user_id, task_id, snapshot_hash, last_briefed)
                    VALUES (:uid, :tid, :hash, :now)
                    ON CONFLICT (user_id, task_id)
                    DO UPDATE SET snapshot_hash = EXCLUDED.snapshot_hash,
                                  last_briefed = EXCLUDED.last_briefed
                """).bindparams(
                    uid=user_id,
                    tid=task_id,
                    hash=compute_task_hash(task),
                    now=now,
                )
            )
        await session.commit()


# ── Internal data gather ──────────────────────────────────────────────────────

async def _gather_internal(user_id: int) -> dict:
    """Collect tasks, calendar events, and project data."""
    from fabledassistant.services.notes import list_notes
    from fabledassistant.services.projects import list_projects
    from fabledassistant.services.caldav import is_caldav_configured, list_events

    today = date.today().isoformat()

    # Tasks: overdue, due today, high priority in-progress
    all_tasks: list[dict] = []
    try:
        all_task_objs, _total = await list_notes(user_id, is_task=True, limit=100)
        all_tasks = [
            {
                "task_id": t.id,
                "title": t.title,
                "status": t.status,
                "due_date": t.due_date.isoformat() if t.due_date else None,
                "priority": t.priority,
            }
            for t in all_task_objs
        ]
        overdue = [
            format_task(t) for t in all_tasks
            if t.get("due_date") and t["due_date"] < today and t.get("status") != "done"
        ]
        due_today = [
            format_task(t) for t in all_tasks
            if t.get("due_date") == today and t.get("status") != "done"
        ]
        high_priority = [
            format_task(t) for t in all_tasks
            if t.get("priority") == "high" and t.get("status") not in ("done",) and
               format_task(t) not in overdue and format_task(t) not in due_today
        ][:5]
    except Exception:
        logger.warning("Failed to gather tasks for briefing", exc_info=True)
        overdue, due_today, high_priority = [], [], []

    # Calendar events today
    calendar_events = []
    try:
        if await is_caldav_configured(user_id):
            events = await list_events(user_id, start=today, end=today)
            calendar_events = [
                f"{e.get('summary', 'Event')} at {e.get('dtstart', 'unknown time')}"
                for e in (events or [])
            ]
    except Exception:
        logger.warning("Failed to gather calendar events for briefing", exc_info=True)

    # Projects: active projects
    projects_summary = []
    try:
        projects = await list_projects(user_id)
        for p in projects[:5]:
            projects_summary.append(p.title or "Untitled project")
    except Exception:
        logger.warning("Failed to gather projects for briefing", exc_info=True)

    return {
        "date": today,
        "overdue_tasks": overdue,
        "due_today": due_today,
        "high_priority": high_priority,
        "calendar_events": calendar_events,
        "active_projects": projects_summary,
        "all_tasks_raw": all_tasks,
    }


# ── External data gather ──────────────────────────────────────────────────────

async def _gather_external(user_id: int) -> dict:
    """Collect RSS items and weather."""
    from fabledassistant.services.rss import get_recent_items
    from fabledassistant.services.weather import get_cached_weather

    rss_items, weather = await asyncio.gather(
        get_recent_items(user_id, limit=20),
        get_cached_weather(user_id),
        return_exceptions=True,
    )
    return {
        "rss_items": rss_items if not isinstance(rss_items, Exception) else [],
        "weather": weather if not isinstance(weather, Exception) else [],
    }


# ── LLM synthesis ─────────────────────────────────────────────────────────────

async def _llm_synthesise(system_prompt: str, user_prompt: str, model: str) -> str:
    """Single non-streaming LLM call. Returns the assistant's response text."""
    payload = {
        "model": model,
        "messages": [
            {"role": "system", "content": system_prompt},
            {"role": "user", "content": user_prompt},
        ],
        "stream": False,
        "options": {"num_ctx": 4096, "temperature": 0.4},
    }
    try:
        async with httpx.AsyncClient(timeout=120.0) as client:
            resp = await client.post(f"{Config.OLLAMA_URL}/api/chat", json=payload)
            resp.raise_for_status()
            data = resp.json()
            return data.get("message", {}).get("content", "").strip()
    except Exception:
        logger.warning("LLM synthesis failed", exc_info=True)
        return ""


def _internal_system_prompt(profile_body: str) -> str:
    return (
        "You are a personal briefing assistant. Your job is to give the user a clear, "
        "concise summary of their internal workload: tasks, calendar, and projects. "
        "Be direct and prioritised — lead with what's urgent. Use plain text with light "
        "markdown. Do not include weather or news.\n\n"
        + (f"User profile:\n{profile_body}\n" if profile_body else "")
    )


def _external_system_prompt() -> str:
    return (
        "You are a briefing assistant for external information. Your job is to present "
        "selected news items and summarise any remaining RSS content. "
        "IMPORTANT: Weather is handled separately — do NOT include any weather section.\n\n"
        "Format each news item EXACTLY as:\n"
        "**[Headline text](source_url)**\n"
        "*Outlet Name · Day Month*\n"
        "One or two sentence summary.\n\n"
        "Present news items in the EXACT ORDER they are provided. Do not reorder them. "
        "After the news cards, add a brief paragraph for any remaining context."
    )


def _internal_user_prompt(data: dict, slot: str) -> str:
    lines = [f"Briefing slot: {slot}", f"Date: {data['date']}", ""]
    if data.get("unchanged_task_count", 0) > 0:
        lines.append(
            f"({data['unchanged_task_count']} tasks are unchanged since the last briefing "
            "— acknowledge briefly, do not list them.)"
        )
        lines.append("")
    changed = data.get("changed_tasks") or data.get("overdue_tasks", [])
    if changed:
        lines.append(f"CHANGED/NEW TASKS ({len(changed)}):")
        lines.extend(f"  - {t}" for t in changed)
        lines.append("")
    if data.get("due_today"):
        lines.append(f"DUE TODAY ({len(data['due_today'])}):")
        lines.extend(f"  - {t}" for t in data["due_today"])
        lines.append("")
    if data.get("high_priority"):
        lines.append("HIGH PRIORITY (in progress):")
        lines.extend(f"  - {t}" for t in data["high_priority"])
        lines.append("")
    if data["calendar_events"]:
        lines.append("CALENDAR TODAY:")
        lines.extend(f"  - {e}" for e in data["calendar_events"])
        lines.append("")
    if data["active_projects"]:
        lines.append(f"ACTIVE PROJECTS: {', '.join(data['active_projects'])}")
    return "\n".join(lines)


def _format_temp(value: float, unit: str) -> str:
    """Convert Celsius to the requested unit and format as an integer string."""
    if unit == "F":
        return f"{value * 9 / 5 + 32:.0f}"
    return f"{value:.0f}"


def _external_user_prompt(data: dict, slot: str, temp_unit: str = "C") -> str:
    unit_sym = f"°{temp_unit}"
    lines = [f"Briefing slot: {slot}", ""]
    if data["weather"]:
        lines.append("WEATHER:")
        for loc in data["weather"]:
            lines.append(f"  {loc['location_label']}:")
            for day in loc["days"][:3]:
                t_min = _format_temp(day["temp_min"], temp_unit)
                t_max = _format_temp(day["temp_max"], temp_unit)
                lines.append(
                    f"    {day['date']}: {day['description']}, "
                    f"{t_min}–{t_max}{unit_sym}, {day['precip_mm']}mm rain"
                )
            if loc["changes_since_last_fetch"]:
                lines.append("  FORECAST CHANGES:")
                lines.extend(f"    - {c}" for c in loc["changes_since_last_fetch"])
        lines.append("")
    if data["rss_items"]:
        lines.append(f"RSS DIGEST ({len(data['rss_items'])} items):")
        for item in data["rss_items"][:15]:
            lines.append(f"  [{item.get('feed_title', 'Feed')}] {item['title']}")
            if item.get("content"):
                lines.append(f"    {item['content'][:200]}")
    return "\n".join(lines)


# ── Main entry point ───────────────────────────────────────────────────────────

async def _get_temp_unit(user_id: int) -> str:
    """Read the user's preferred temperature unit from briefing_config ('C' or 'F')."""
    import json
    raw = await get_setting(user_id, "briefing_config", "{}")
    try:
        config = json.loads(raw) if isinstance(raw, str) else (raw or {})
        unit = config.get("temp_unit", "C")
        return unit if unit in ("C", "F") else "C"
    except Exception:
        return "C"


async def run_compilation(
    user_id: int,
    slot: str,
    model: str | None = None,
) -> tuple[str, dict]:
    """
    Run the full two-lane briefing pipeline for a user and slot.
    Returns (briefing_text, metadata_dict) where metadata contains
    weather card data and rss_item_ids for frontend rendering.
    """
    if model is None:
        model = await get_setting(user_id, "default_model", Config.OLLAMA_MODEL)

    from fabledassistant.services.briefing_profile import get_profile_body
    from fabledassistant.services.briefing_preferences import (
        load_topic_preferences,
        load_topic_reaction_scores,
        score_and_filter_items,
    )
    from fabledassistant.services.weather import parse_weather_card_data, get_cached_weather_rows

    profile_body, temp_unit = await asyncio.gather(
        get_profile_body(user_id),
        _get_temp_unit(user_id),
    )

    # ── Pre-processing ──────────────────────────────────────────────────────────
    include_topics, exclude_topics = await load_topic_preferences(user_id)
    topic_scores = await load_topic_reaction_scores(user_id)

    # Parallel raw gather — weather rows fetched in same gather to avoid extra DB round-trip
    internal_data, external_data, weather_rows = await asyncio.gather(
        _gather_internal(user_id),
        _gather_external(user_id),
        get_cached_weather_rows(user_id),
    )

    # Task change detection
    all_tasks = internal_data.get("all_tasks_raw", [])
    changed_tasks, unchanged_count = await split_changed_tasks(user_id, all_tasks)

    # RSS filtering
    raw_rss = external_data.get("rss_items") or []
    filtered_rss = score_and_filter_items(
        raw_rss,
        include_topics=include_topics,
        exclude_topics=exclude_topics,
        topic_scores=topic_scores,
        max_items=10,
    )
    rss_item_ids = [item["id"] for item in filtered_rss if item.get("id")]

    # Weather staleness gate — returns None if data is >24h old
    weather_card = parse_weather_card_data(weather_rows[0], temp_unit) if weather_rows else None

    # ── LLM Synthesis ──────────────────────────────────────────────────────────
    # Build filtered internal data with only changed tasks
    today = internal_data["date"]
    internal_data_filtered = dict(internal_data)
    internal_data_filtered["unchanged_task_count"] = unchanged_count
    internal_data_filtered["changed_tasks"] = [format_task(t) for t in changed_tasks]

    # Build filtered external data (suppress weather prose — card handles it)
    external_data_filtered = {
        "rss_items": filtered_rss,
        "weather": [],
    }

    internal_text, external_text = await asyncio.gather(
        _llm_synthesise(
            _internal_system_prompt(profile_body),
            _internal_user_prompt(internal_data_filtered, slot),
            model,
        ),
        _llm_synthesise(
            _external_system_prompt(),
            _external_user_prompt(external_data_filtered, slot, temp_unit),
            model,
        ),
    )

    # ── Post-processing ─────────────────────────────────────────────────────────
    await upsert_task_snapshots(user_id, all_tasks)

    metadata: dict = {"rss_item_ids": rss_item_ids, "weather": weather_card}

    if not internal_text and not external_text:
        logger.warning("Briefing compilation produced no content for user %d slot %s", user_id, slot)
        return "", metadata

    greeting = slot_greeting(slot)
    parts = [f"**{greeting} — {today}**", ""]
    if internal_text:
        parts += ["## Your Day", "", internal_text, ""]
    if external_text:
        parts += ["## The World", "", external_text]

    return "\n".join(parts).strip(), metadata


async def run_slot_injection(user_id: int, slot: str, model: str | None = None) -> str:
    """
    Lighter update for 8am/12pm/4pm — gathers fresh data and produces a slot-specific
    update prompt. Returns the text to inject as a new user→assistant exchange.
    """
    if model is None:
        model = await get_setting(user_id, "default_model", Config.OLLAMA_MODEL)

    internal_data, external_data, temp_unit = await asyncio.gather(
        _gather_internal(user_id),
        _gather_external(user_id),
        _get_temp_unit(user_id),
    )

    system = (
        f"You are a briefing assistant providing a {slot} update. Be brief — "
        "the user has already seen the morning briefing. Focus on what's changed or new."
    )
    user_prompt = (
        f"Slot: {slot}\n\n"
        + _internal_user_prompt(internal_data, slot)
        + "\n\n"
        + _external_user_prompt(external_data, slot, temp_unit)
    )
    return await _llm_synthesise(system, user_prompt, model)