import { randomBytes, randomInt, randomUUID } from "node:crypto";
import { HttpStatus, Inject, Injectable } from "@nestjs/common";
import { ErrorCode } from "@drift/contracts";
import type { Prisma } from "@prisma/client";
import { DomainException } from "../common/domain.exception.js";
import { PrismaService } from "../database/prisma.service.js";
import { utc8UsageDate } from "../bottle/usage-date.js";
import {
  decryptLeaseToken,
  encryptLeaseToken,
  leaseHmac,
} from "../auth/auth.config.js";
import { CandidateRepository, type Candidate } from "./candidate.repository.js";
import {
  CandidateBatchContended,
  classifyPickError,
  readMatchRetryConfig,
  transactionLimits,
} from "./match-retry-policy.js";
import { SafetyLockService } from "../safety/safety-lock.service.js";

type LeaseWithBottle = {
  id: string;
  expiresAt: Date;
  leaseTokenCiphertext: Uint8Array;
  bottle: {
    id: string;
    authorId: string;
    contentText: string;
    author: {
      anonymousProfile: {
        publicId: string;
        nickname: string;
        avatarColor: string;
        bio: string | null;
      } | null;
    };
  };
};

function positiveInt(
  value: string | undefined,
  fallback: number,
  name: string,
) {
  const parsed = value === undefined ? fallback : Number(value);
  if (!Number.isInteger(parsed) || parsed <= 0)
    throw new Error(`${name} must be a positive integer`);
  return parsed;
}

@Injectable()
export class MatchService {
  private readonly ttlMs = positiveInt(
    process.env.BOTTLE_LEASE_TTL_MS,
    300_000,
    "BOTTLE_LEASE_TTL_MS",
  );
  private readonly retry = readMatchRetryConfig(process.env);

  constructor(
    @Inject(PrismaService) private readonly prisma: PrismaService,
    @Inject(CandidateRepository)
    private readonly candidates: CandidateRepository,
    @Inject(SafetyLockService) private readonly locks: SafetyLockService,
  ) {}

  async pick(pickerId: string, requestId: string) {
    const deadline = performance.now() + this.retry.budgetMs;
    for (let attempt = 0; attempt < this.retry.maxAttempts; attempt += 1) {
      const limits = transactionLimits(this.retry, performance.now(), deadline);
      if (!limits) break;
      try {
        const result = await this.prisma.$transaction(
          async (tx) => {
            const previous = await this.findPrevious(tx, pickerId, requestId);
            if (previous?.lease) {
              await this.locks.lockAccounts(tx, [
                pickerId,
                previous.lease.bottle.authorId,
              ]);
              await this.assertPairAllowed(
                tx,
                pickerId,
                previous.lease.bottle.authorId,
              );
              return this.replayResponse(previous.lease);
            }
            await this.assertEligible(tx, pickerId);
            const usageDate = utc8UsageDate(new Date());
            const batch = await this.candidates.findBatch(tx, pickerId);
            if (!batch.length) {
              // An in-flight same-key winner may have claimed the sole bottle
              // without committing its request row yet. Let it commit before
              // deciding this request actually saw an empty pool.
              await this.locks.lockAccounts(tx, [pickerId]);
              if (await this.findPrevious(tx, pickerId, requestId))
                throw new CandidateBatchContended();
              throw new DomainException(
                ErrorCode.BOTTLE_POOL_EMPTY,
                "Bottle pool empty",
                HttpStatus.NOT_FOUND,
              );
            }
            // Lock the entire subject set once, in global order. Locking pairs
            // across candidates could otherwise form A→B / B→A cycles. This
            // trades wider short-lived locks for correctness; the concurrent
            // sole-bottle and same-key retry E2E cases exercise contention.
            await this.locks.lockAccounts(tx, [
              pickerId,
              ...batch.map((candidate) => candidate.authorId),
            ]);
            while (batch.length) {
              const index = Math.floor(Math.random() * batch.length);
              const candidate = batch.splice(index, 1)[0]!;
              const result = await this.claim(
                tx,
                pickerId,
                requestId,
                usageDate,
                candidate,
              );
              if (result) return result;
            }
            throw new CandidateBatchContended();
          },
          {
            isolationLevel: "ReadCommitted",
            ...limits,
          },
        );
        return result;
      } catch (error) {
        if (error instanceof DomainException) {
          if (error.code === ErrorCode.BOTTLE_POOL_EMPTY) {
            try {
              const winner = await this.readWinnerUntil(
                pickerId,
                requestId,
                Math.min(deadline, performance.now() + 250),
              );
              if (winner) return winner;
            } catch (readError) {
              if (classifyPickError(readError) === "SERVICE_UNAVAILABLE")
                throw error;
              throw readError;
            }
          }
          throw error;
        }
        const action = classifyPickError(error);
        if (action === "THROW") throw error;
        if (action === "SERVICE_UNAVAILABLE") break;
        if (action === "READ_WINNER") {
          try {
            const winner = await this.readWinner(pickerId, requestId, deadline);
            if (winner) return winner;
          } catch (readError) {
            if (classifyPickError(readError) === "SERVICE_UNAVAILABLE") break;
            throw readError;
          }
        }
      }
      const remaining = deadline - performance.now();
      if (remaining <= 1) break;
      await new Promise((resolve) =>
        setTimeout(
          resolve,
          Math.min(
            randomInt(5, 21) * 2 ** Math.min(attempt, 3),
            100,
            remaining,
          ),
        ),
      );
    }
    throw new DomainException(
      ErrorCode.SERVICE_UNAVAILABLE,
      "Bottle pick temporarily unavailable",
      HttpStatus.SERVICE_UNAVAILABLE,
    );
  }

  private findPrevious(
    client: Prisma.TransactionClient | PrismaService,
    pickerId: string,
    requestId: string,
  ) {
    return client.bottlePickRequest.findUnique({
      where: { pickerId_requestId: { pickerId, requestId } },
      include: {
        lease: {
          include: {
            bottle: {
              include: { author: { include: { anonymousProfile: true } } },
            },
          },
        },
      },
    });
  }

  private async readWinner(
    pickerId: string,
    requestId: string,
    deadline: number,
  ) {
    const limits = transactionLimits(this.retry, performance.now(), deadline);
    if (!limits) return null;
    const result = await this.prisma.$transaction(
      async (tx) => {
        const previous = await this.findPrevious(tx, pickerId, requestId);
        if (!previous?.lease) return null;
        await this.locks.lockAccounts(tx, [
          pickerId,
          previous.lease.bottle.authorId,
        ]);
        await this.assertPairAllowed(
          tx,
          pickerId,
          previous.lease.bottle.authorId,
        );
        return this.replayResponse(previous.lease);
      },
      { isolationLevel: "ReadCommitted", ...limits },
    );
    return result;
  }

  private async readWinnerUntil(
    pickerId: string,
    requestId: string,
    deadline: number,
  ) {
    while (performance.now() < deadline) {
      const winner = await this.readWinner(pickerId, requestId, deadline);
      if (winner) return winner;
      await new Promise((resolve) => setTimeout(resolve, 5));
    }
    return null;
  }

  private async claim(
    tx: Prisma.TransactionClient,
    pickerId: string,
    requestId: string,
    usageDate: string,
    candidate: Candidate,
  ) {
    await this.assertPairAllowed(tx, pickerId, candidate.authorId);
    const eligible = await tx.bottle.findFirst({
      where: {
        id: candidate.id,
        authorId: candidate.authorId,
        version: candidate.version,
        reviewStatus: "APPROVED",
        poolStatus: "IN_POOL",
        activeLeaseId: null,
        author: { anonymousProfile: { reviewStatus: "APPROVED" } },
        pickHistory: { none: { pickerId } },
      },
      select: { id: true },
    });
    if (!eligible) return null;
    const token = randomBytes(32).toString("base64url");
    const expiresAt = new Date(Date.now() + this.ttlMs);
    const leaseId = randomUUID();
    const claimed = await tx.bottle.updateMany({
      where: {
        id: candidate.id,
        version: candidate.version,
        poolStatus: "IN_POOL",
        activeLeaseId: null,
      },
      data: {
        poolStatus: "LEASED",
        activeLeaseId: leaseId,
        version: { increment: 1 },
      },
    });
    if (claimed.count !== 1) return null;
    const lease = await tx.bottlePickLease.create({
      data: {
        id: leaseId,
        bottleId: candidate.id,
        pickerId,
        leaseTokenHash: leaseHmac(token),
        leaseTokenCiphertext: encryptLeaseToken(token, leaseId),
        expiresAt,
      },
    });
    await tx.bottlePickHistory.create({
      data: { bottleId: candidate.id, pickerId },
    });
    const rows = await tx.$queryRaw<Array<{ bottles_picked: number }>>`
      INSERT INTO "daily_usage" ("id", "account_id", "usage_date", "bottles_picked", "updated_at")
      VALUES (gen_random_uuid(), ${pickerId}::uuid, ${usageDate}::date, 1, now())
      ON CONFLICT ("account_id", "usage_date") DO UPDATE
      SET "bottles_picked" = "daily_usage"."bottles_picked" + 1, "updated_at" = now()
      WHERE "daily_usage"."bottles_picked" < 20
      RETURNING "bottles_picked"`;
    if (!rows.length) this.limit();
    await tx.bottlePickRequest.create({
      data: { pickerId, requestId, leaseId: lease.id },
    });
    return {
      bottle: { id: candidate.id, contentText: candidate.contentText },
      author: {
        publicId: candidate.publicId,
        nickname: candidate.nickname,
        avatarColor: candidate.avatarColor,
        bio: candidate.bio,
      },
      lease: { id: lease.id, token, expiresAt },
    };
  }

  private async assertEligible(tx: Prisma.TransactionClient, pickerId: string) {
    const now = new Date();
    const account = await tx.account.findUnique({
      where: { id: pickerId },
      select: { status: true },
    });
    const sanction = await tx.sanction.findFirst({
      where: {
        accountId: pickerId,
        type: { in: ["SUSPENSION", "BAN"] },
        revokedAt: null,
        startsAt: { lte: now },
        OR: [{ expiresAt: null }, { expiresAt: { gt: now } }],
      },
      select: { id: true },
    });
    if (account?.status !== "ACTIVE" || sanction)
      throw new DomainException(
        ErrorCode.ACCOUNT_SANCTIONED,
        "Account sanctioned",
        HttpStatus.FORBIDDEN,
      );
  }

  private async assertPairAllowed(
    tx: Prisma.TransactionClient,
    pickerId: string,
    authorId: string,
  ) {
    const now = new Date();
    const [accounts, block, sanction] = await Promise.all([
      tx.account.count({
        where: { id: { in: [pickerId, authorId] }, status: "ACTIVE" },
      }),
      tx.block.findFirst({
        where: {
          OR: [
            { blockerId: pickerId, blockedId: authorId },
            { blockerId: authorId, blockedId: pickerId },
          ],
        },
        select: { id: true },
      }),
      tx.sanction.findFirst({
        where: {
          accountId: { in: [pickerId, authorId] },
          type: { in: ["SUSPENSION", "BAN"] },
          revokedAt: null,
          startsAt: { lte: now },
          OR: [{ expiresAt: null }, { expiresAt: { gt: now } }],
        },
        select: { id: true },
      }),
    ]);
    if (block)
      throw new DomainException(
        ErrorCode.USER_BLOCKED,
        "User blocked",
        HttpStatus.FORBIDDEN,
      );
    if (accounts !== 2 || sanction)
      throw new DomainException(
        ErrorCode.ACCOUNT_SANCTIONED,
        "Account sanctioned",
        HttpStatus.FORBIDDEN,
      );
  }

  private replayResponse(lease: LeaseWithBottle) {
    try {
      return this.response(
        lease,
        decryptLeaseToken(lease.leaseTokenCiphertext, lease.id),
      );
    } catch (error) {
      if (error instanceof DomainException) throw error;
      throw new DomainException(
        ErrorCode.SERVICE_UNAVAILABLE,
        "Bottle pick temporarily unavailable",
        HttpStatus.SERVICE_UNAVAILABLE,
      );
    }
  }

  async returnBottle(
    pickerId: string,
    bottleId: string,
    leaseId: string,
    token: string,
  ) {
    const tokenHash = leaseHmac(token);
    const hidden = () =>
      new DomainException(
        ErrorCode.NOT_FOUND,
        "Not Found",
        HttpStatus.NOT_FOUND,
      );
    return this.prisma.$transaction(async (tx) => {
      const rows = await tx.$queryRaw<
        Array<{ id: string; status: string; expiresAt: Date }>
      >`
        SELECT "id", "status", "expires_at" AS "expiresAt"
        FROM "bottle_pick_leases"
        WHERE "id" = ${leaseId}::uuid AND "bottle_id" = ${bottleId}::uuid
          AND "picker_id" = ${pickerId}::uuid AND "lease_token_hash" = ${tokenHash}
        FOR UPDATE`;
      const lease = rows[0];
      if (!lease) throw hidden();
      if (lease.status === "RETURNED")
        return { bottleId, leaseId, status: "RETURNED" as const };
      if (lease.status !== "ACTIVE") throw hidden();
      if (lease.expiresAt <= new Date())
        throw new DomainException(
          ErrorCode.BOTTLE_LEASE_EXPIRED,
          "Bottle lease expired",
          HttpStatus.GONE,
        );
      const released = await tx.bottle.updateMany({
        where: { id: bottleId, poolStatus: "LEASED", activeLeaseId: leaseId },
        data: {
          poolStatus: "IN_POOL",
          activeLeaseId: null,
          version: { increment: 1 },
        },
      });
      if (released.count !== 1) throw hidden();
      await tx.bottlePickLease.update({
        where: { id: leaseId },
        data: { status: "RETURNED", endedAt: new Date() },
      });
      return { bottleId, leaseId, status: "RETURNED" as const };
    });
  }

  private response(lease: LeaseWithBottle, token: string) {
    const profile = lease.bottle.author.anonymousProfile;
    if (!profile)
      throw new DomainException(
        ErrorCode.BOTTLE_POOL_EMPTY,
        "Bottle pool empty",
        HttpStatus.NOT_FOUND,
      );
    return {
      bottle: { id: lease.bottle.id, contentText: lease.bottle.contentText },
      author: {
        publicId: profile.publicId,
        nickname: profile.nickname,
        avatarColor: profile.avatarColor,
        bio: profile.bio,
      },
      lease: { id: lease.id, token, expiresAt: lease.expiresAt },
    };
  }

  private limit(): never {
    throw new DomainException(
      ErrorCode.BOTTLE_DAILY_LIMIT,
      "Daily pick limit reached",
      HttpStatus.TOO_MANY_REQUESTS,
    );
  }
}