finance-app/src/app/api/rules/apply/route.ts

import { NextRequest, NextResponse } from "next/server";
import { getCurrentUser } from "@/lib/auth";
import { queryRaw } from "@/lib/db";
import { getTransactions } from "@/lib/queries";
import { evaluateCondition, type Condition, type Actions } from "@/lib/rules";

interface SnapshotEntry {
  transaction_id: number;
  had_override: boolean;
  prev_category_override: string | null;
  prev_merchant_normalized: string | null;
  prev_tag_ids: number[];
  prev_splits: { participant_id: number; share_percent: number; settled: boolean }[];
}


export async function GET(req: NextRequest) {
  const user = await getCurrentUser(req);
  if (!user) return NextResponse.json({ error: "Unauthorized" }, { status: 403 });

  const runs = await queryRaw<{
    id: number;
    applied_at: string;
    split_from: string | null;
    matched: number;
    transactions_affected: number;
    reverted_at: string | null;
  }>(
    `SELECT id, applied_at, split_from, matched, transactions_affected, reverted_at
     FROM rule_apply_runs WHERE owner_id = $1 ORDER BY applied_at DESC LIMIT 20`,
    [user.id]
  );

  return NextResponse.json(runs);
}

export async function POST(req: NextRequest) {
  const user = await getCurrentUser(req);
  if (!user) return NextResponse.json({ error: "Unauthorized" }, { status: 403 });

  const body = await req.json().catch(() => ({})) as { splitFrom?: string | null; ruleId?: number | null };
  const splitFrom = body.splitFrom || null;
  const ruleId = body.ruleId || null;

  const rules = await queryRaw<{ id: number; conditions: unknown; actions: unknown }>(
    ruleId
      ? `SELECT id, conditions, actions FROM rules WHERE owner_id = $1 AND id = $2`
      : `SELECT id, conditions, actions FROM rules WHERE owner_id = $1 AND enabled = true ORDER BY priority DESC`,
    ruleId ? [user.id, ruleId] : [user.id]
  );

  if (!rules.length) return NextResponse.json({ matched: 0, transactions_affected: 0 });

  const { data: transactions } = await getTransactions(user.id, { limit: 100000, offset: 0 });

  // --- Pre-pass: find all transactions that will match any rule ---
  const parsedRules = rules.map((r) => ({
    conditions: (typeof r.conditions === "string" ? JSON.parse(r.conditions) : r.conditions) as Condition[],
    actions: (typeof r.actions === "string" ? JSON.parse(r.actions) : r.actions) as Actions,
  }));

  const matchedIds = new Set<number>();
  for (const tx of transactions) {
    for (const { conditions } of parsedRules) {
      if (conditions.length === 0 || conditions.every((c) => evaluateCondition(c, tx))) {
        matchedIds.add(tx.id);
        break;
      }
    }
  }

  // --- Capture before-state for all matched transactions (batched) ---
  const snapshot: SnapshotEntry[] = [];
  if (matchedIds.size > 0) {
    const ids = Array.from(matchedIds);
    const idList = ids.join(",");

    const overrides = await queryRaw<{ transaction_id: number; category_override: string | null; merchant_normalized: string | null }>(
      `SELECT transaction_id, category_override, merchant_normalized FROM transaction_overrides WHERE transaction_id = ANY($1::int[])`,
      [ids]
    );
    const overrideMap = new Map(overrides.map((o) => [o.transaction_id, o]));

    const tagRows = await queryRaw<{ transaction_id: number; tag_id: number }>(
      `SELECT transaction_id, tag_id FROM transaction_tags WHERE transaction_id = ANY($1::int[])`,
      [ids]
    );
    const tagMap = new Map<number, number[]>();
    for (const row of tagRows) {
      if (!tagMap.has(row.transaction_id)) tagMap.set(row.transaction_id, []);
      tagMap.get(row.transaction_id)!.push(row.tag_id);
    }

    const splitRows = await queryRaw<{ transaction_id: number; participant_id: number; share_percent: number; settled: boolean }>(
      `SELECT transaction_id, participant_id, share_percent, settled FROM transaction_splits WHERE transaction_id = ANY($1::int[])`,
      [ids]
    );
    const splitMap = new Map<number, { participant_id: number; share_percent: number; settled: boolean }[]>();
    for (const row of splitRows) {
      if (!splitMap.has(row.transaction_id)) splitMap.set(row.transaction_id, []);
      splitMap.get(row.transaction_id)!.push({ participant_id: row.participant_id, share_percent: row.share_percent, settled: row.settled });
    }

    for (const id of ids) {
      const ov = overrideMap.get(id);
      snapshot.push({
        transaction_id: id,
        had_override: !!ov,
        prev_category_override: ov?.category_override ?? null,
        prev_merchant_normalized: ov?.merchant_normalized ?? null,
        prev_tag_ids: tagMap.get(id) ?? [],
        prev_splits: splitMap.get(id) ?? [],
      });
    }

    void idList; // suppress unused warning
  }

  // --- Apply rules ---
  let matched = 0;
  const affectedIds = new Set<number>();

  for (const { conditions, actions } of parsedRules) {
    for (const tx of transactions) {
      const allMatch = conditions.length === 0 || conditions.every((c) => evaluateCondition(c, tx));
      if (!allMatch) continue;

      matched++;
      affectedIds.add(tx.id);

      if (actions.set_category || actions.set_merchant) {
        await queryRaw(
          `INSERT INTO transaction_overrides (transaction_id, category_override, merchant_normalized)
           VALUES ($1, $2, $3)
           ON CONFLICT (transaction_id) DO UPDATE SET
             category_override = COALESCE($2, transaction_overrides.category_override),
             merchant_normalized = COALESCE($3, transaction_overrides.merchant_normalized),
             updated_at = NOW()`,
          [tx.id, actions.set_category || null, actions.set_merchant || null]
        );
      }

      if (actions.add_tag_ids?.length) {
        for (const tagId of actions.add_tag_ids) {
          await queryRaw(
            `INSERT INTO transaction_tags (transaction_id, tag_id) VALUES ($1, $2) ON CONFLICT DO NOTHING`,
            [tx.id, tagId]
          );
        }
      }

      if (actions.apply_split?.length) {
        if (splitFrom && tx.transaction_date < splitFrom) continue;
        // Remove only participants no longer in the rule's split, and upsert the
        // rest — a plain delete+reinsert would reset settled flags on every run.
        await queryRaw(
          `DELETE FROM transaction_splits WHERE transaction_id = $1 AND participant_id != ALL($2::int[])`,
          [tx.id, actions.apply_split.map((s) => s.participant_id)]
        );
        for (const s of actions.apply_split) {
          await queryRaw(
            `INSERT INTO transaction_splits (transaction_id, participant_id, share_percent)
             VALUES ($1, $2, $3)
             ON CONFLICT (transaction_id, participant_id)
             DO UPDATE SET share_percent = EXCLUDED.share_percent`,
            [tx.id, s.participant_id, s.share_percent]
          );
        }
      }
    }
  }

  // --- Save run record ---
  const run = await queryRaw<{ id: number }>(
    `INSERT INTO rule_apply_runs (owner_id, split_from, matched, transactions_affected, snapshot)
     VALUES ($1, $2, $3, $4, $5) RETURNING id`,
    [user.id, splitFrom, matched, affectedIds.size, JSON.stringify(snapshot)]
  );

  return NextResponse.json({ id: run[0].id, matched, transactions_affected: affectedIds.size });
}