# -*- coding: utf-8 -*-
# Copyright (c) 2025 relakkes@gmail.com
#
# This file is part of MediaCrawler project.
# Repository: https://github.com/NanmiCoder/MediaCrawler/blob/main/api/monitor/report.py
# GitHub: https://github.com/NanmiCoder
# Licensed under NON-COMMERCIAL LEARNING LICENSE 1.1
#
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"""Cross-task reporting: what grew, and what is new, over a date range.

Two families of numbers that answer different questions and are therefore kept
as separate columns:

* **互动增量** — Σ(current − previous) across the selected notes. "How many likes
  did this set of notes gain?"
* **新增内容** — count of newly discovered notes and comments. "How much new
  material showed up?"

The per-day interaction delta is defined as *last value on the day* minus *last
value before the day* (0 when the note was first seen on that day). That keeps
growth from a note's first observation counted once, rather than smeared across
every later day.

Aggregation runs in Python over the snapshots rather than as one large SQL
query: the per-note-per-day baseline lookup is a windowed operation that SQLite
expresses awkwardly, and the row counts here are small enough that clarity is
worth more than the query planner.
"""

from bisect import bisect_right
from datetime import date, datetime, time, timedelta
from typing import Any, Dict, Iterable, List, Optional, Sequence

from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession

from .models import MonitorComment, MonitorNote, MonitorNoteMetric

METRIC_FIELDS = ("liked_count", "comment_count", "collected_count", "share_count")

METRIC_LABELS = {
    "liked_count": "点赞",
    "comment_count": "评论",
    "collected_count": "收藏",
    "share_count": "分享",
}


def day_bounds(day: date) -> tuple[int, int]:
    """Inclusive epoch-millisecond bounds for a local calendar day."""
    start = datetime.combine(day, time.min)
    end = datetime.combine(day, time.max)
    return int(start.timestamp() * 1000), int(end.timestamp() * 1000)


def iter_days(start: date, end: date) -> List[date]:
    days = []
    cursor = start
    while cursor <= end:
        days.append(cursor)
        cursor += timedelta(days=1)
    return days


def compute_daily_rows(
    series_by_note: Dict[str, List[tuple[int, Dict[str, Optional[int]]]]],
    notes_per_day: Dict[date, int],
    comments_per_day: Dict[date, int],
    days: Sequence[date],
) -> List[Dict[str, Any]]:
    """Pure aggregation. ``series_by_note`` must be sorted by timestamp ascending."""
    prepared = {note_id: ([ts for ts, _ in points], points) for note_id, points in series_by_note.items()}

    rows: List[Dict[str, Any]] = []
    for day in days:
        day_start, day_end = day_bounds(day)
        totals = {field: 0 for field in METRIC_FIELDS}
        # Records *which* metric could not be compared, not just that something
        # could not. A blanket flag loses all value the moment one permanently
        # unparseable field makes every row "incomplete".
        partial_metrics: set[str] = set()

        for times, points in prepared.values():
            end_index = bisect_right(times, day_end) - 1
            if end_index < 0:
                # Not yet tracked on this day.
                continue

            end_values = points[end_index][1]
            start_index = bisect_right(times, day_start - 1) - 1
            # No earlier snapshot means the note first appeared in this window,
            # so it starts from zero -- all of its count is genuinely new.
            start_values = (
                points[start_index][1] if start_index >= 0 else {f: 0 for f in METRIC_FIELDS}
            )

            for field in METRIC_FIELDS:
                end_value, start_value = end_values.get(field), start_values.get(field)
                if end_value is None or start_value is None:
                    # An unparseable count on either side makes the delta unknown;
                    # skipping beats reporting a fabricated number.
                    partial_metrics.add(field)
                    continue
                totals[field] += end_value - start_value

        row: Dict[str, Any] = {
            "date": day.isoformat(),
            "new_notes": notes_per_day.get(day, 0),
            "new_comments": comments_per_day.get(day, 0),
            "partial_metrics": sorted(partial_metrics),
        }
        row.update({f"{field}_delta": value for field, value in totals.items()})
        rows.append(row)

    return rows


async def build_report(
    session: AsyncSession,
    task_ids: Optional[Iterable[int]],
    start_day: date,
    end_day: date,
) -> Dict[str, Any]:
    """Daily rows plus totals for the selected tasks over the given date range."""
    start_ms, _ = day_bounds(start_day)
    _, end_ms = day_bounds(end_day)

    scope = list(task_ids) if task_ids else None
    days = iter_days(start_day, end_day)

    # Fetch every snapshot up to the range end: the delta on the first day needs
    # the last value from *before* the range, so a lower bound would be wrong.
    metric_stmt = select(MonitorNoteMetric).where(MonitorNoteMetric.captured_at <= end_ms)
    if scope is not None:
        metric_stmt = metric_stmt.where(MonitorNoteMetric.task_id.in_(scope))
    metric_stmt = metric_stmt.order_by(MonitorNoteMetric.note_id, MonitorNoteMetric.run_id)

    series_by_note: Dict[str, List[tuple[int, Dict[str, Optional[int]]]]] = {}
    included_note_ids: set[str] = set()
    for snapshot in (await session.scalars(metric_stmt)).all():
        included_note_ids.add(snapshot.note_id)
        series_by_note.setdefault(snapshot.note_id, []).append(
            (
                snapshot.captured_at,
                {field: getattr(snapshot, field) for field in METRIC_FIELDS},
            )
        )

    note_stmt = select(MonitorNote.first_seen_at).where(
        MonitorNote.first_seen_at >= start_ms, MonitorNote.first_seen_at <= end_ms
    )
    if scope is not None:
        note_stmt = note_stmt.where(MonitorNote.task_id.in_(scope))

    comment_stmt = select(MonitorComment.first_seen_at).where(
        MonitorComment.first_seen_at >= start_ms, MonitorComment.first_seen_at <= end_ms
    )
    if scope is not None:
        comment_stmt = comment_stmt.where(MonitorComment.task_id.in_(scope))

    notes_per_day = _count_by_day((await session.scalars(note_stmt)).all())
    comments_per_day = _count_by_day((await session.scalars(comment_stmt)).all())

    rows = compute_daily_rows(series_by_note, notes_per_day, comments_per_day, days)

    totals = {
        "new_notes": sum(row["new_notes"] for row in rows),
        "new_comments": sum(row["new_comments"] for row in rows),
    }
    for field in METRIC_FIELDS:
        totals[f"{field}_delta"] = sum(row[f"{field}_delta"] for row in rows)

    return {
        "start_date": start_day.isoformat(),
        "end_date": end_day.isoformat(),
        "task_ids": scope,
        "rows": rows,
        "totals": totals,
        "note_count": len(included_note_ids),
        "has_partial_data": any(row["partial_metrics"] for row in rows),
        "partial_metrics": sorted({field for row in rows for field in row["partial_metrics"]}),
        "metric_labels": METRIC_LABELS,
    }


def _count_by_day(timestamps: Iterable[Optional[int]]) -> Dict[date, int]:
    counts: Dict[date, int] = {}
    for ts in timestamps:
        if ts is None:
            continue
        day = datetime.fromtimestamp(ts / 1000).date()
        counts[day] = counts.get(day, 0) + 1
    return counts