#!/usr/bin/env python3
"""
Migration: Rescue misrouted viewing reviews.

Two classes of bad data this script fixes:

  CLASS A — person_reviews collection
    dm_brain.py (before the bug fix) wrote viewing reviews to a legacy
    `person_reviews` collection using field `reviewed_id` instead of
    `target_id`.  These docs never showed up on the landlord's profile.

  CLASS B — reviews collection with ObjectId target_id
    viewing_notification_jobs.py stored `landlord_id` (a raw ObjectId) in
    the pending_viewing_review session, so dm_brain wrote the review with
    target_id = <ObjectId object> instead of a plain string.  MongoDB's
    $match on the string version found nothing.

Both classes are migrated into `reviews` with:
    target_type  = "user"
    target_id    = str(landlord_id)
    review_source = "viewing"

After migrating, all affected users' ratings are recalculated from scratch.

Run:
    python scripts/migrate_viewing_reviews.py          # dry-run (shows what would change)
    python scripts/migrate_viewing_reviews.py --apply  # actually writes to MongoDB
"""

import asyncio
import sys
import os
from datetime import datetime

sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))

from motor.motor_asyncio import AsyncIOMotorClient
from bson import ObjectId
from app.config import settings

DRY_RUN = "--apply" not in sys.argv


# ── helpers ──────────────────────────────────────────────────────────────────

def _str_id(val) -> str:
    """Safely coerce ObjectId or string to string."""
    if val is None:
        return ""
    return str(val)


async def _get_db():
    client = AsyncIOMotorClient(settings.MONGODB_URL, serverSelectionTimeoutMS=5000)
    await client.admin.command("ping")
    return client[settings.MONGODB_DATABASE]


def _is_objectid(val) -> bool:
    return isinstance(val, ObjectId)


async def _find_in_reviews(db, reviewer_id: str, target_id: str):
    """Return matching review doc from canonical collection, or None."""
    return await db.reviews.find_one({
        "reviewer_id": reviewer_id,
        "target_type": "user",
        "target_id": target_id,
    })


async def _already_in_reviews(db, reviewer_id: str, target_id: str) -> bool:
    return await _find_in_reviews(db, reviewer_id, target_id) is not None


async def _recalculate_user_rating(db, user_id: str):
    """Recompute rating / reviews_count for one user from the reviews collection."""
    reviews = await db.reviews.find({
        "target_type": "user",
        "target_id": user_id,
    }).to_list(length=None)

    count = len(reviews)
    avg   = round(sum(r.get("rating", 0) for r in reviews) / count, 2) if count else 0.0

    if not DRY_RUN:
        await db.users.update_one(
            {"_id": ObjectId(user_id)},
            {"$set": {"rating": avg, "reviews_count": count}},
        )
    return count, avg


# ── CLASS A — migrate from person_reviews ────────────────────────────────────

async def migrate_person_reviews(db) -> list[str]:
    """
    Move docs from `person_reviews` into `reviews`.
    Returns list of affected landlord user_ids.
    """
    print("\n" + "=" * 60)
    print("CLASS A — person_reviews collection")
    print("=" * 60)

    docs = await db["person_reviews"].find({}).to_list(length=None)
    print(f"Found {len(docs)} document(s) in person_reviews")

    if not docs:
        return []

    affected_users: list[str] = []
    migrated = skipped = errors = 0

    for doc in docs:
        doc_id = doc["_id"]

        # Field mapping: old schema used `reviewed_id` as the landlord's id
        raw_target = doc.get("reviewed_id") or doc.get("target_id")
        if not raw_target:
            print(f"  ⚠  Doc {doc_id}: no reviewed_id / target_id — skipping")
            errors += 1
            continue

        target_id   = _str_id(raw_target)
        reviewer_id = _str_id(doc.get("reviewer_id", ""))

        if not target_id or not reviewer_id:
            print(f"  ⚠  Doc {doc_id}: missing reviewer_id or target_id — skipping")
            errors += 1
            continue

        # If the review already exists in the canonical collection, check whether
        # it's missing review_source="viewing" (saved before today's schema change).
        existing = await _find_in_reviews(db, reviewer_id, target_id)
        if existing:
            needs_patch = existing.get("review_source") != "viewing"
            property_name_old = (
                doc.get("property_name") or doc.get("property") or
                existing.get("property_name") or ""
            )
            if needs_patch:
                print(f"  ~  Doc {doc_id}: in reviews but missing review_source=viewing — patching")
                if not DRY_RUN:
                    patch = {"review_source": "viewing"}
                    if property_name_old:
                        patch["property_name"] = property_name_old
                    await db["reviews"].update_one(
                        {"_id": existing["_id"]},
                        {"$set": patch},
                    )
                affected_users.append(target_id)
                migrated += 1
            else:
                print(f"  ✓  Doc {doc_id}: already correct in reviews — skipping")
                skipped += 1
            continue

        # Build canonical review doc
        new_doc = {
            "target_type":   "user",
            "target_id":     target_id,
            "reviewer_id":   reviewer_id,
            "reviewer_name": doc.get("reviewer_name") or "",
            "rating":        doc.get("rating", 0),
            "review_text":   doc.get("review_text") or doc.get("comment") or "",
            "created_at":    doc.get("created_at", datetime.utcnow()),
            "review_source": "viewing",
            "property_name": doc.get("property_name") or doc.get("property") or "",
        }

        landlord_name = "(unknown)"
        landlord = await db["users"].find_one({"_id": ObjectId(target_id)}) \
            if ObjectId.is_valid(target_id) else None
        if landlord:
            landlord_name = f"{landlord.get('firstName','')} {landlord.get('lastName','')}".strip()

        print(f"  → Migrating doc {doc_id}: "
              f"{new_doc['rating']}★ by {reviewer_id} "
              f"for landlord {landlord_name} ({target_id})")

        if not DRY_RUN:
            await db["reviews"].insert_one(new_doc)
            # Mark the old doc so we know it's been processed (don't delete yet)
            await db["person_reviews"].update_one(
                {"_id": doc_id},
                {"$set": {"_migrated": True, "_migrated_at": datetime.utcnow()}},
            )

        affected_users.append(target_id)
        migrated += 1

    print(f"\n  Migrated: {migrated}  |  Already present: {skipped}  |  Errors: {errors}")
    return affected_users


# ── CLASS B — fix ObjectId target_id in reviews ──────────────────────────────

async def fix_objectid_target_ids(db) -> list[str]:
    """
    Find user reviews in `reviews` where target_id is a BSON ObjectId
    (not a string) and convert them to strings.
    Returns list of affected landlord user_ids.
    """
    print("\n" + "=" * 60)
    print("CLASS B — reviews with ObjectId target_id")
    print("=" * 60)

    # Motor returns ObjectId fields as Python ObjectId objects; we can match
    # documents where target_id is not a string by checking the $type operator.
    # BSON type 7 = ObjectId, type 2 = string.
    cursor = db["reviews"].find({
        "target_type": "user",
        "target_id":   {"$type": "objectId"},   # stored as ObjectId, should be string
    })
    docs = await cursor.to_list(length=None)
    print(f"Found {len(docs)} review(s) with ObjectId target_id")

    affected_users: list[str] = []

    for doc in docs:
        doc_id      = doc["_id"]
        old_val     = doc["target_id"]          # ObjectId
        new_val     = str(old_val)              # string

        reviewer_id = _str_id(doc.get("reviewer_id", ""))

        landlord = await db["users"].find_one({"_id": old_val})
        landlord_name = ""
        if landlord:
            landlord_name = f"{landlord.get('firstName','')} {landlord.get('lastName','')}".strip()

        print(f"  → Fix doc {doc_id}: target_id {old_val} → '{new_val}' "
              f"(landlord: {landlord_name or 'not found'})")

        if not DRY_RUN:
            await db["reviews"].update_one(
                {"_id": doc_id},
                {"$set": {
                    "target_id":     new_val,
                    "review_source": doc.get("review_source") or "viewing",
                }},
            )

        affected_users.append(new_val)

    print(f"\n  Fixed: {len(docs)}")
    return affected_users


# ── Rating recalculation ──────────────────────────────────────────────────────

async def recalculate_affected_ratings(db, user_ids: list[str]):
    print("\n" + "=" * 60)
    print("Recalculating ratings for affected landlords")
    print("=" * 60)

    unique_ids = list(set(uid for uid in user_ids if uid and ObjectId.is_valid(uid)))
    if not unique_ids:
        print("  No users to update.")
        return

    for uid in unique_ids:
        user = await db["users"].find_one({"_id": ObjectId(uid)})
        name = ""
        if user:
            name = f"{user.get('firstName','')} {user.get('lastName','')}".strip()

        count, avg = await _recalculate_user_rating(db, uid)
        flag = "" if DRY_RUN else " ✅"
        print(f"  {name or uid}: {count} review(s), avg {avg}★{flag}")


# ── main ─────────────────────────────────────────────────────────────────────

async def main():
    print("\n" + "=" * 60)
    print("VIEWING REVIEWS MIGRATION")
    if DRY_RUN:
        print("MODE: DRY RUN — no changes will be written")
        print("      Pass --apply to commit changes")
    else:
        print("MODE: APPLY — changes will be written to MongoDB")
    print("=" * 60)
    print(f"Started: {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}")

    db = await _get_db()
    print(f"Connected  —  db: {settings.MONGODB_DATABASE}")

    affected_a = await migrate_person_reviews(db)
    affected_b = await fix_objectid_target_ids(db)

    all_affected = affected_a + affected_b
    await recalculate_affected_ratings(db, all_affected)

    print("\n" + "=" * 60)
    total = len(affected_a) + len(affected_b)
    if DRY_RUN:
        print(f"DRY RUN COMPLETE — {total} review(s) would be fixed.")
        print("Run with --apply to commit.")
    else:
        print(f"MIGRATION COMPLETE — {total} review(s) fixed.")
    print(f"Finished: {datetime.now().strftime('%Y-%m-%d %H:%M:%S')}")
    print("=" * 60)


if __name__ == "__main__":
    asyncio.run(main())