import { McpContext, Resolver, Tool } from '@nestjs-mcp/server';
import { z } from 'zod';
import { TaskStreamApi, type TaskStreamClient } from '../api/taskstream-api';
import { issueRef, projectRef } from './params';
import { issueLine } from './summaries';
import { toolResult } from './tool-result';

const READ = { readOnlyHint: true, openWorldHint: false } as const;
const WRITE = {
  readOnlyHint: false,
  destructiveHint: false,
  openWorldHint: false,
} as const;

const PRIORITY = z.enum(['LOWEST', 'LOW', 'MEDIUM', 'HIGH', 'CRITICAL']);

const UUID = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;

/**
 * How the work is organised: epics and the tickets hanging from them, the
 * backlog order, changes to many tickets at once and the trash.
 */
@Resolver()
export class BacklogResolver {
  constructor(private readonly api: TaskStreamApi) {}

  @Tool({
    name: 'list_epics',
    description:
      'Epics of a project (top-level tickets that group others) with the progress of the tickets hanging from each one.',
    paramsSchema: z.object({ project: projectRef }),
    annotations: READ,
  })
  epics({ project }: { project: string }, ctx: McpContext) {
    return toolResult(async () =>
      (
        await this.api.data(
          this.api.as(ctx).GET('/api/projects/{project}/epics', {
            params: { path: { project } },
          }),
        )
      ).map((epic) => ({
        ...issueLine(epic.issue),
        startDate: epic.issue.startDate,
        progress: epic.progress,
      })),
    );
  }

  @Tool({
    name: 'set_issue_parent',
    description:
      'Place a ticket under an epic or another ticket of the same project (three levels at most: epic → ticket → subtask), or back to the top (null).',
    paramsSchema: z.object({
      issue: issueRef,
      parent: z.string().nullable().describe('Epic or ticket key, or null'),
    }),
    annotations: { ...WRITE, idempotentHint: true },
  })
  setParent(
    { issue, parent }: { issue: string; parent: string | null },
    ctx: McpContext,
  ) {
    return toolResult(() =>
      this.api.data(
        this.api.as(ctx).PUT('/api/issues/{issue}/parent', {
          params: { path: { issue } },
          body: { parent },
        }),
      ),
    );
  }

  @Tool({
    name: 'rank_issue',
    description:
      'Move a ticket in the backlog (board columns follow the same order): say which ticket ends up right above it or right below it; above null puts it at the top, below null at the bottom.',
    paramsSchema: z.object({
      issue: issueRef,
      above: z
        .string()
        .nullable()
        .optional()
        .describe('Ticket that ends up right above (null: to the top)'),
      below: z
        .string()
        .nullable()
        .optional()
        .describe('Ticket that ends up right below (null: to the bottom)'),
    }),
    annotations: { ...WRITE, idempotentHint: true },
  })
  rank(
    params: { issue: string; above?: string | null; below?: string | null },
    ctx: McpContext,
  ) {
    const { issue, ...body } = params;
    return toolResult(() =>
      this.api.data(
        this.api.as(ctx).PUT('/api/issues/{issue}/rank', {
          params: { path: { issue } },
          body,
        }),
      ),
    );
  }

  @Tool({
    name: 'bulk_update_issues',
    description:
      'The same change on up to 100 tickets: status, assignee, sprint, release, priority, extra labels. Each ticket follows the normal rules and may refuse on its own; the answer says which.',
    paramsSchema: z.object({
      issues: z.array(issueRef).min(1).max(100),
      status: z.string().optional().describe('Status id'),
      assigneeId: z.string().optional().describe('User id of a member'),
      unassign: z.boolean().optional(),
      sprintId: z.string().optional(),
      noSprint: z.boolean().optional().describe('Back to the backlog'),
      releaseId: z.string().optional(),
      noRelease: z.boolean().optional().describe('Out of their release'),
      priority: PRIORITY.optional(),
      addLabels: z.array(z.string().max(40)).max(20).optional(),
    }),
    annotations: WRITE,
  })
  bulk(
    params: {
      issues: string[];
      status?: string;
      assigneeId?: string;
      unassign?: boolean;
      sprintId?: string;
      noSprint?: boolean;
      releaseId?: string;
      noRelease?: boolean;
      priority?: z.infer<typeof PRIORITY>;
      addLabels?: string[];
    },
    ctx: McpContext,
  ) {
    const { issues, ...change } = params;
    return toolResult(async () => {
      const client = this.api.as(ctx);
      const refs = await this.ids(client, issues);
      const answer = await this.api.data(
        client.POST('/api/issues/bulk', {
          body: { issueIds: refs.map((r) => r.id), ...change },
        }),
      );
      const keyOf = new Map(refs.map((r) => [r.id, r.ref]));
      return {
        updated: answer.updated,
        refused: answer.results
          .filter((r) => !r.ok)
          .map((r) => ({ issue: keyOf.get(r.issueId), error: r.error })),
      };
    });
  }

  @Tool({
    name: 'delete_issue',
    description:
      'Move a ticket to the trash (whoever opened it, or an owner/admin). It disappears everywhere; restore_issue brings it back within 30 days, then it is deleted for good.',
    paramsSchema: z.object({ issue: issueRef }),
    annotations: { readOnlyHint: false, destructiveHint: true },
  })
  trash({ issue }: { issue: string }, ctx: McpContext) {
    return toolResult(() =>
      this.api.data(
        this.api.as(ctx).DELETE('/api/issues/{issue}', {
          params: { path: { issue } },
        }),
      ),
    );
  }

  @Tool({
    name: 'restore_issue',
    description: 'Bring a ticket back from the trash.',
    paramsSchema: z.object({ issue: issueRef }),
    annotations: { ...WRITE, idempotentHint: true },
  })
  restore({ issue }: { issue: string }, ctx: McpContext) {
    return toolResult(() =>
      this.api.data(
        this.api.as(ctx).POST('/api/issues/{issue}/restore', {
          params: { path: { issue } },
        }),
      ),
    );
  }

  @Tool({
    name: 'list_trash',
    description: "A project's tickets in the trash, newest first.",
    paramsSchema: z.object({ project: projectRef }),
    annotations: READ,
  })
  listTrash({ project }: { project: string }, ctx: McpContext) {
    return toolResult(async () =>
      (
        await this.api.data(
          this.api.as(ctx).GET('/api/projects/{project}/trash', {
            params: { path: { project } },
          }),
        )
      ).map((issue) => ({ ...issueLine(issue), trashedAt: issue.trashedAt })),
    );
  }

  /**
   * The bulk endpoint takes ids; people and models talk in keys. Keys are
   * looked up a few at a time, ids pass as they are.
   */
  private async ids(
    client: TaskStreamClient,
    refs: string[],
  ): Promise<{ ref: string; id: string }[]> {
    const found: { ref: string; id: string }[] = [];
    for (let i = 0; i < refs.length; i += 10) {
      const batch = refs.slice(i, i + 10);
      found.push(
        ...(await Promise.all(
          batch.map(async (ref) =>
            UUID.test(ref)
              ? { ref, id: ref }
              : {
                  ref,
                  id: (
                    await this.api.data(
                      client.GET('/api/issues/{issue}', {
                        params: { path: { issue: ref } },
                      }),
                    )
                  ).id,
                },
          ),
        )),
      );
    }
    return found;
  }
}