/**
 * TasksClient — external-dependency interface for the tasks package.
 *
 * All code in tools.ts codes against the TasksClient interface, never against a
 * concrete AWS SDK import. The real implementation (DynamoDBTasksClient) stubs
 * the actual DynamoDB call so no AWS credentials or network are needed at import
 * time or in tests.
 *
 * Tests inject a MockTasksClient (see test/tasks.test.ts).
 */

export interface Task {
  taskId: string;
  sub: string; // owner — partition key, enforced ABAC (dynamodb:LeadingKeys)
  title: string;
  description?: string;
  completed: boolean;
  createdAt: string; // ISO-8601
  completedAt?: string; // ISO-8601
}

export interface CreateTaskInput {
  sub: string;
  title: string;
  description?: string;
}

export interface ListTasksInput {
  sub: string;
  includeCompleted?: boolean;
}

export interface CompleteTaskInput {
  sub: string;
  taskId: string;
}

export interface DeleteTaskInput {
  sub: string;
  taskId: string;
}

/**
 * The interface every caller (tools.ts, jobs, tests) depends on.
 * The DynamoDB table is partitioned by `sub`; callers always pass their own sub
 * so the ABAC LeadingKeys condition on the IAM policy matches.
 */
export interface TasksClient {
  createTask(input: CreateTaskInput): Promise<Task>;
  listTasks(input: ListTasksInput): Promise<Task[]>;
  completeTask(input: CompleteTaskInput): Promise<Task>;
  deleteTask(input: DeleteTaskInput): Promise<void>;
}

// ---------------------------------------------------------------------------
// Real (DynamoDB) implementation
// ---------------------------------------------------------------------------
// The real AWS SDK import is lazy and guard-wrapped so that:
//   1. Importing this file at test time does NOT instantiate a real SDK client.
//   2. A real deployment provides TABLE_NAME and AWS credentials via the
//      Lambda execution environment.
//
// TODO (DEFERRED — auth layer): Once the real JWT/aud/client_id validation
// layer is in place, ensure the DynamoDB client is constructed with a role that
// only has `dynamodb:GetItem`, `dynamodb:PutItem`, `dynamodb:UpdateItem`,
// `dynamodb:DeleteItem`, `dynamodb:Query` on the tasks table, scoped to
// `dynamodb:LeadingKeys` = `${cognito-identity.amazonaws.com:sub}` so a
// compromised server cannot read another user's tasks.

const TABLE_NAME = process.env['TASKS_TABLE_NAME'] ?? 'sh-mcp-tasks';

export class DynamoDBTasksClient implements TasksClient {
  // eslint-disable-next-line @typescript-eslint/no-explicit-any
  private ddb: any; // typed as `any` to avoid importing @aws-sdk/client-dynamodb at the top level

  constructor() {
    if (process.env['NODE_ENV'] === 'test') {
      throw new Error(
        'DynamoDBTasksClient must not be instantiated in tests. Inject a mock TasksClient instead.',
      );
    }
    // Lazy import — only reached in a real Lambda execution environment.
    // eslint-disable-next-line @typescript-eslint/no-require-imports
    const { DynamoDBClient } = require('@aws-sdk/client-dynamodb');
    // eslint-disable-next-line @typescript-eslint/no-require-imports
    const { DynamoDBDocumentClient } = require('@aws-sdk/lib-dynamodb');
    this.ddb = DynamoDBDocumentClient.from(new DynamoDBClient({}));
    // Accessed once so TypeScript does not flag the field as write-only.
    // Remove when the real DynamoDB calls are wired in the methods below.
    void this.ddb;
  }

  async createTask(input: CreateTaskInput): Promise<Task> {
    // TODO: replace this stub with a real `PutCommand` against TABLE_NAME.
    // Stub guards against accidental real calls during development.
    throw new Error(
      `DynamoDBTasksClient.createTask not yet implemented. Table: ${TABLE_NAME}, input: ${JSON.stringify(input)}`,
    );
  }

  async listTasks(input: ListTasksInput): Promise<Task[]> {
    // TODO: replace with a real `QueryCommand` (KeyConditionExpression: 'sub = :sub',
    // optionally FilterExpression: 'completed = :completed').
    throw new Error(
      `DynamoDBTasksClient.listTasks not yet implemented. Table: ${TABLE_NAME}, input: ${JSON.stringify(input)}`,
    );
  }

  async completeTask(input: CompleteTaskInput): Promise<Task> {
    // TODO: replace with a real `UpdateCommand` setting completed = true, completedAt = now.
    // Enforce ownership: ConditionExpression: 'sub = :sub' so a user cannot complete another
    // user's task even if they guess the taskId.
    throw new Error(
      `DynamoDBTasksClient.completeTask not yet implemented. Table: ${TABLE_NAME}, input: ${JSON.stringify(input)}`,
    );
  }

  async deleteTask(input: DeleteTaskInput): Promise<void> {
    // TODO: replace with a real `DeleteCommand` with the same sub-ownership condition.
    throw new Error(
      `DynamoDBTasksClient.deleteTask not yet implemented. Table: ${TABLE_NAME}, input: ${JSON.stringify(input)}`,
    );
  }
}