"""Match FIT files to activity rows by content (session.start_time).

The Garmin Connect data export embeds activity IDs in FIT filenames
(`<id>_<name>.fit`), so `ingest_export.py` can index them straight from the
filename. The newer Garmin **Takeout** dump uses upload IDs instead
(`<email>_<upload_id>.fit`), which are a different ID space, so filename-based
linking fails. This script does the linking via FIT content: it opens each FIT,
reads the `session.start_time` (UTC), and matches it against
`activities.start_time_gmt` within a small tolerance.

Usage:
    uv run link_fit_files.py <export_root>
    uv run link_fit_files.py <export_root> --dry-run --min-size-kb 50

Defaults:
    Only parses FITs >= 50 KB (workout FITs; smaller files are HRV/sleep/body-battery
    monitoring snapshots, ~99% of the dump by count).
    Tolerance: 60 seconds. Garmin sometimes rounds session start to the second
    while activities.start_time_gmt is also second-precision.

Re-running is safe — the table is upsert by activity_id.
"""

from __future__ import annotations

import argparse
import sqlite3
import sys
from datetime import datetime, timezone
from pathlib import Path

import fitparse

from db import connect


def _parse_session_start(fit_path: Path) -> datetime | None:
    """Return the session start_time as a UTC datetime, or None if the file has none."""
    try:
        fit = fitparse.FitFile(str(fit_path))
        for msg in fit.get_messages("session"):
            vals = msg.get_values()
            ts = vals.get("start_time")
            if ts is None:
                continue
            if isinstance(ts, datetime):
                # fitparse returns naive datetimes in UTC for FIT timestamps.
                return ts.replace(tzinfo=timezone.utc) if ts.tzinfo is None else ts.astimezone(timezone.utc)
        return None
    except Exception as exc:  # noqa: BLE001
        print(f"  ! parse failed for {fit_path.name}: {exc}", file=sys.stderr)
        return None


def _load_activity_index(conn: sqlite3.Connection) -> dict[int, int]:
    """Map (epoch_seconds_utc) -> activity_id for every activity with a start_time_gmt."""
    idx: dict[int, int] = {}
    for aid, gmt in conn.execute("SELECT activity_id, start_time_gmt FROM activities"):
        if gmt is None:
            continue
        # start_time_gmt may be an ISO string, ms epoch number, or sec epoch.
        try:
            if isinstance(gmt, (int, float)):
                v = float(gmt)
                # heuristic: >1e12 means ms epoch, otherwise seconds
                secs = int(v / 1000) if v > 1e12 else int(v)
            else:
                s = str(gmt).strip().rstrip("Z")
                secs = int(datetime.fromisoformat(s).replace(tzinfo=timezone.utc).timestamp())
        except (ValueError, TypeError):
            continue
        idx[secs] = aid
    return idx


def link(export_root: Path, *, dry_run: bool, min_size_kb: int, tolerance_s: int) -> None:
    if not export_root.exists():
        sys.exit(f"path does not exist: {export_root}")

    conn = connect()
    index = _load_activity_index(conn)
    if not index:
        sys.exit("no activities with start_time_gmt — ingest activities first")
    sorted_keys = sorted(index.keys())
    print(f"loaded {len(index):,} activity start times")

    candidates = [p for p in export_root.rglob("*.fit") if p.stat().st_size >= min_size_kb * 1024]
    print(f"scanning {len(candidates):,} FIT files ≥ {min_size_kb} KB")

    linked = unmatched = parse_failed = 0
    for i, p in enumerate(candidates, 1):
        if i % 50 == 0:
            print(f"  … {i}/{len(candidates)} processed (linked={linked}, unmatched={unmatched})")
        start = _parse_session_start(p)
        if start is None:
            parse_failed += 1
            continue
        target = int(start.timestamp())
        # Binary search the closest key within tolerance.
        from bisect import bisect_left

        pos = bisect_left(sorted_keys, target)
        candidates_near: list[int] = []
        if pos < len(sorted_keys):
            candidates_near.append(sorted_keys[pos])
        if pos > 0:
            candidates_near.append(sorted_keys[pos - 1])
        best = min((c for c in candidates_near if abs(c - target) <= tolerance_s), default=None, key=lambda c: abs(c - target))
        if best is None:
            unmatched += 1
            continue
        aid = index[best]
        if not dry_run:
            rel = p.relative_to(export_root)
            conn.execute(
                """INSERT OR REPLACE INTO activity_fit_files (activity_id, fit_path, indexed_at)
                   VALUES (?, ?, datetime('now'))""",
                (aid, str(rel)),
            )
        linked += 1

    if not dry_run:
        conn.commit()
    conn.close()

    print()
    print("=== linker summary ===")
    print(f"  candidates scanned: {len(candidates):,}")
    print(f"  linked            : {linked:,}" + ("  (dry-run)" if dry_run else ""))
    print(f"  unmatched start   : {unmatched:,}  (no activity within ±{tolerance_s}s)")
    print(f"  parse failures    : {parse_failed:,}")


def main() -> None:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("export_root", help="Path to the unzipped Garmin export folder")
    parser.add_argument("--dry-run", action="store_true")
    parser.add_argument("--min-size-kb", type=int, default=50,
                        help="Skip FITs smaller than this; default 50 KB filters out HRV/sleep snapshots")
    parser.add_argument("--tolerance-s", type=int, default=60,
                        help="Max seconds between FIT session start and activity start to count as a match")
    args = parser.parse_args()
    link(Path(args.export_root).expanduser().resolve(),
         dry_run=args.dry_run,
         min_size_kb=args.min_size_kb,
         tolerance_s=args.tolerance_s)


if __name__ == "__main__":
    main()