import { Injectable } from "@nestjs/common";
import type {
  AgentMessage,
  AgentMessageRole,
  AgentSession,
  AgentSessionList,
  AgentSessionStatus,
  IAgentProvider,
  InjectResult,
} from "@mosaic/shared";
import type { AgentConversationMessage, AgentSessionTree } from "@prisma/client";
import { AgentControlService } from "./agent-control.service";
import { AgentMessagesService } from "./agent-messages.service";
import { AgentTreeService } from "./agent-tree.service";

const DEFAULT_SESSION_LIMIT = 50;
const DEFAULT_MESSAGE_LIMIT = 50;
const MAX_MESSAGE_LIMIT = 200;
const STREAM_POLL_INTERVAL_MS = 1000;
const INTERNAL_OPERATOR_ID = "internal-provider";

@Injectable()
export class InternalAgentProvider implements IAgentProvider {
  readonly providerId = "internal";
  readonly providerType = "internal";
  readonly displayName = "Internal Orchestrator";

  constructor(
    private readonly messagesService: AgentMessagesService,
    private readonly controlService: AgentControlService,
    private readonly treeService: AgentTreeService
  ) {}

  async listSessions(cursor?: string, limit = DEFAULT_SESSION_LIMIT): Promise<AgentSessionList> {
    const {
      sessions,
      total,
      cursor: nextCursor,
    } = await this.treeService.listSessions(cursor, limit);

    return {
      sessions: sessions.map((session) => this.toAgentSession(session)),
      total,
      ...(nextCursor !== undefined ? { cursor: nextCursor } : {}),
    };
  }

  async getSession(sessionId: string): Promise<AgentSession | null> {
    const session = await this.treeService.getSession(sessionId);
    return session ? this.toAgentSession(session) : null;
  }

  async getMessages(
    sessionId: string,
    limit = DEFAULT_MESSAGE_LIMIT,
    before?: string
  ): Promise<AgentMessage[]> {
    const safeLimit = this.normalizeMessageLimit(limit);
    const skip = this.parseSkip(before);

    const result = await this.messagesService.getMessages(sessionId, safeLimit, skip);
    return result.messages.map((message) => this.toAgentMessage(message));
  }

  async injectMessage(sessionId: string, content: string): Promise<InjectResult> {
    await this.controlService.injectMessage(sessionId, INTERNAL_OPERATOR_ID, content);

    return {
      accepted: true,
    };
  }

  async pauseSession(sessionId: string): Promise<void> {
    await this.controlService.pauseAgent(sessionId, INTERNAL_OPERATOR_ID);
  }

  async resumeSession(sessionId: string): Promise<void> {
    await this.controlService.resumeAgent(sessionId, INTERNAL_OPERATOR_ID);
  }

  async killSession(sessionId: string, force = true): Promise<void> {
    await this.controlService.killAgent(sessionId, INTERNAL_OPERATOR_ID, force);
  }

  async *streamMessages(sessionId: string): AsyncIterable<AgentMessage> {
    const replayMessages = await this.messagesService.getReplayMessages(
      sessionId,
      DEFAULT_MESSAGE_LIMIT
    );

    let lastSeenTimestamp = new Date();
    let lastSeenMessageId: string | null = null;

    for (const message of replayMessages) {
      yield this.toAgentMessage(message);
      lastSeenTimestamp = message.timestamp;
      lastSeenMessageId = message.id;
    }

    for (;;) {
      const newMessages = await this.messagesService.getMessagesAfter(
        sessionId,
        lastSeenTimestamp,
        lastSeenMessageId
      );

      for (const message of newMessages) {
        yield this.toAgentMessage(message);
        lastSeenTimestamp = message.timestamp;
        lastSeenMessageId = message.id;
      }

      await this.delay(STREAM_POLL_INTERVAL_MS);
    }
  }

  isAvailable(): Promise<boolean> {
    return Promise.resolve(true);
  }

  private toAgentSession(session: AgentSessionTree): AgentSession {
    const metadata = this.toMetadata(session.metadata);

    return {
      id: session.sessionId,
      providerId: this.providerId,
      providerType: this.providerType,
      ...(session.taskId !== null ? { label: session.taskId } : {}),
      status: this.toSessionStatus(session.status),
      ...(session.parentSessionId !== null ? { parentSessionId: session.parentSessionId } : {}),
      createdAt: session.spawnedAt,
      updatedAt: session.completedAt ?? session.spawnedAt,
      ...(metadata !== undefined ? { metadata } : {}),
    };
  }

  private toAgentMessage(message: AgentConversationMessage): AgentMessage {
    const metadata = this.toMetadata(message.metadata);

    return {
      id: message.id,
      sessionId: message.sessionId,
      role: this.toMessageRole(message.role),
      content: message.content,
      timestamp: message.timestamp,
      ...(metadata !== undefined ? { metadata } : {}),
    };
  }

  private toSessionStatus(status: string): AgentSessionStatus {
    switch (status) {
      case "running":
        return "active";
      case "paused":
        return "paused";
      case "completed":
        return "completed";
      case "failed":
      case "killed":
        return "failed";
      case "spawning":
      default:
        return "idle";
    }
  }

  private toMessageRole(role: string): AgentMessageRole {
    switch (role) {
      case "agent":
      case "assistant":
        return "assistant";
      case "system":
        return "system";
      case "tool":
        return "tool";
      case "operator":
      case "user":
      default:
        return "user";
    }
  }

  private normalizeMessageLimit(limit: number): number {
    const normalized = Number.isFinite(limit) ? Math.trunc(limit) : DEFAULT_MESSAGE_LIMIT;
    if (normalized < 1) {
      return 1;
    }

    return Math.min(normalized, MAX_MESSAGE_LIMIT);
  }

  private parseSkip(before?: string): number {
    if (!before) {
      return 0;
    }

    const parsed = Number.parseInt(before, 10);
    if (Number.isNaN(parsed) || parsed < 0) {
      return 0;
    }

    return parsed;
  }

  private toMetadata(value: unknown): Record<string, unknown> | undefined {
    if (value !== null && typeof value === "object" && !Array.isArray(value)) {
      return value as Record<string, unknown>;
    }

    return undefined;
  }

  private async delay(ms: number): Promise<void> {
    await new Promise((resolve) => {
      setTimeout(resolve, ms);
    });
  }
}