/**
 * In-memory fake of the Mongo collections used by the service. Production runs
 * MongoDB 3.2, for which no mongod binary is downloadable/runnable on modern
 * dev/CI hosts (glibc/libssl). So the DB integration tests run against this
 * fake, which faithfully emulates the subset of behaviour the code relies on:
 * the query operators used ($ne/$in/$gte/$exists/equality), $set/$unset updates,
 * projection/limit, and — crucially — unique-index duplicate-key errors (11000)
 * that back the idempotency guarantee.
 */
import type { Repos } from '../src/db.js';

type Doc = Record<string, any>;

function isObjectId(v: any): boolean {
  return v != null && typeof v === 'object' && typeof v.equals === 'function' && v._bsontype === 'ObjectID';
}

function valEq(a: any, b: any): boolean {
  if (a === b) return true;
  if (a == null || b == null) return a === b;
  if (isObjectId(a)) {
    try {
      return a.equals(b);
    } catch {
      return false;
    }
  }
  if (isObjectId(b)) return b.equals(a);
  if (a instanceof Date && b instanceof Date) return a.getTime() === b.getTime();
  return false;
}

function isOperatorObject(cond: any): boolean {
  if (cond == null || typeof cond !== 'object') return false;
  if (cond instanceof Date || isObjectId(cond)) return false;
  const keys = Object.keys(cond);
  return keys.length > 0 && keys.every((k) => k.startsWith('$'));
}

function matchField(docVal: any, cond: any): boolean {
  if (isOperatorObject(cond)) {
    return Object.entries(cond).every(([op, v]) => {
      switch (op) {
        case '$ne':
          return !valEq(docVal, v);
        case '$in':
          return Array.isArray(v) && v.some((x) => valEq(docVal, x));
        case '$gte':
          return docVal != null && docVal >= (v as any);
        case '$gt':
          return docVal != null && docVal > (v as any);
        case '$lte':
          return docVal != null && docVal <= (v as any);
        case '$lt':
          return docVal != null && docVal < (v as any);
        case '$exists':
          return (docVal !== undefined) === v;
        default:
          throw new Error(`fake-repo: unsupported operator ${op}`);
      }
    });
  }
  return valEq(docVal, cond);
}

function matches(doc: Doc, filter: Doc): boolean {
  return Object.entries(filter).every(([k, cond]) => matchField(doc[k], cond));
}

function applyUpdate(doc: Doc, update: Doc): void {
  if (update.$set) Object.assign(doc, update.$set);
  if (update.$unset) for (const k of Object.keys(update.$unset)) delete doc[k];
}

class FakeCollection {
  docs: Doc[] = [];
  collectionName = 'fake';
  private uniqueFields: string[] | null = null;

  async createIndex(spec: Doc, opts?: { unique?: boolean }): Promise<string> {
    if (opts?.unique) this.uniqueFields = Object.keys(spec);
    return 'idx';
  }

  private violatesUnique(doc: Doc): boolean {
    if (!this.uniqueFields) return false;
    return this.docs.some((d) => this.uniqueFields!.every((f) => valEq(d[f], doc[f])));
  }

  async insertOne(doc: Doc): Promise<{ insertedId: any }> {
    if (this.violatesUnique(doc)) {
      const err: any = new Error('E11000 duplicate key error');
      err.code = 11000;
      throw err;
    }
    const copy = { ...doc };
    this.docs.push(copy);
    return { insertedId: copy._id };
  }

  async insertMany(docs: Doc[]): Promise<{ insertedCount: number }> {
    for (const d of docs) await this.insertOne(d);
    return { insertedCount: docs.length };
  }

  async findOne(filter: Doc = {}): Promise<Doc | null> {
    return this.docs.find((d) => matches(d, filter)) ?? null;
  }

  async updateOne(filter: Doc, update: Doc, opts?: { upsert?: boolean }): Promise<{ modifiedCount: number; upsertedCount: number }> {
    const d = this.docs.find((x) => matches(x, filter));
    if (!d) {
      if (opts?.upsert) {
        const created: Doc = { ...filter };
        applyUpdate(created, update);
        this.docs.push(created);
        return { modifiedCount: 0, upsertedCount: 1 };
      }
      return { modifiedCount: 0, upsertedCount: 0 };
    }
    applyUpdate(d, update);
    return { modifiedCount: 1, upsertedCount: 0 };
  }

  async updateMany(filter: Doc, update: Doc): Promise<{ modifiedCount: number }> {
    const ds = this.docs.filter((x) => matches(x, filter));
    for (const d of ds) applyUpdate(d, update);
    return { modifiedCount: ds.length };
  }

  async deleteOne(filter: Doc): Promise<{ deletedCount: number }> {
    const i = this.docs.findIndex((d) => matches(d, filter));
    if (i === -1) return { deletedCount: 0 };
    this.docs.splice(i, 1);
    return { deletedCount: 1 };
  }

  async deleteMany(filter: Doc = {}): Promise<{ deletedCount: number }> {
    const before = this.docs.length;
    this.docs = this.docs.filter((d) => !matches(d, filter));
    return { deletedCount: before - this.docs.length };
  }

  async countDocuments(filter: Doc = {}): Promise<number> {
    return this.docs.filter((d) => matches(d, filter)).length;
  }

  find(filter: Doc = {}, _opts?: Doc) {
    let result = this.docs.filter((d) => matches(d, filter));
    const cursor = {
      project() {
        return cursor;
      },
      sort(spec: Doc) {
        const [field, dir] = Object.entries(spec)[0] as [string, number];
        result = [...result].sort((a, b) => {
          const av = a[field];
          const bv = b[field];
          if (av === bv) return 0;
          return (av < bv ? -1 : 1) * (dir < 0 ? -1 : 1);
        });
        return cursor;
      },
      limit(n: number) {
        result = result.slice(0, n);
        return cursor;
      },
      async toArray() {
        return result.map((d) => ({ ...d }));
      },
    };
    return cursor;
  }
}

export function makeRepos(): Repos {
  return {
    client: {} as any,
    db: {} as any,
    notifications: new FakeCollection() as any,
    users: new FakeCollection() as any,
    sends: new FakeCollection() as any,
    subscriptions: new FakeCollection() as any,
    activefires: new FakeCollection() as any,
    notificationsShadow: new FakeCollection() as any,
    matcherState: new FakeCollection() as any,
    close: async () => {},
  };
}