import { OpenBrainConfigError, OpenBrainHttpError, OpenBrainRequestError } from "./errors.js";

export type OpenBrainThoughtMetadata = Record<string, unknown> & {
  sessionId?: string;
  turn?: number;
  role?: string;
  type?: string;
};

export type OpenBrainThought = {
  id: string;
  content: string;
  source: string;
  metadata: OpenBrainThoughtMetadata | undefined;
  createdAt: string | undefined;
  updatedAt: string | undefined;
  score: number | undefined;
  [key: string]: unknown;
};

export type OpenBrainThoughtInput = {
  content: string;
  source: string;
  metadata?: OpenBrainThoughtMetadata;
};

export type OpenBrainSearchInput = {
  query: string;
  limit: number;
  source?: string;
};

export type OpenBrainClientOptions = {
  baseUrl: string;
  apiKey: string;
  fetchImpl?: typeof fetch;
};

export interface OpenBrainClientLike {
  createThought(input: OpenBrainThoughtInput): Promise<OpenBrainThought>;
  search(input: OpenBrainSearchInput): Promise<OpenBrainThought[]>;
  listRecent(input: { limit: number; source?: string }): Promise<OpenBrainThought[]>;
  updateThought(
    id: string,
    payload: { content?: string; metadata?: OpenBrainThoughtMetadata },
  ): Promise<OpenBrainThought>;
  deleteThought(id: string): Promise<void>;
  deleteThoughts(params: { source?: string; metadataId?: string }): Promise<void>;
}

function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === "object" && value !== null;
}

function readString(record: Record<string, unknown>, key: string): string | undefined {
  const value = record[key];
  return typeof value === "string" ? value : undefined;
}

function readNumber(record: Record<string, unknown>, key: string): number | undefined {
  const value = record[key];
  return typeof value === "number" ? value : undefined;
}

function normalizeBaseUrl(baseUrl: string): string {
  const normalized = baseUrl.trim().replace(/\/+$/, "");
  if (normalized.length === 0) {
    throw new OpenBrainConfigError("Missing required OpenBrain config: baseUrl");
  }
  return normalized;
}

function normalizeApiKey(apiKey: string): string {
  const normalized = apiKey.trim();
  if (normalized.length === 0) {
    throw new OpenBrainConfigError("Missing required OpenBrain config: apiKey");
  }
  return normalized;
}

function normalizeHeaders(headers: unknown): Record<string, string> {
  if (headers === undefined) {
    return {};
  }

  if (Array.isArray(headers)) {
    const normalized: Record<string, string> = {};
    for (const pair of headers) {
      if (!Array.isArray(pair) || pair.length < 2) {
        continue;
      }

      const key = pair[0];
      const value = pair[1];
      if (typeof key !== "string" || typeof value !== "string") {
        continue;
      }

      normalized[key] = value;
    }
    return normalized;
  }

  if (headers instanceof Headers) {
    const normalized: Record<string, string> = {};
    for (const [key, value] of headers.entries()) {
      normalized[key] = value;
    }
    return normalized;
  }

  if (!isRecord(headers)) {
    return {};
  }

  const normalized: Record<string, string> = {};
  for (const [key, value] of Object.entries(headers)) {
    if (typeof value === "string") {
      normalized[key] = value;
      continue;
    }

    if (Array.isArray(value)) {
      normalized[key] = value.join(", ");
    }
  }

  return normalized;
}

async function readResponseBody(response: Response): Promise<string | undefined> {
  try {
    const body = await response.text();
    return body.length > 0 ? body : undefined;
  } catch {
    return undefined;
  }
}

export class OpenBrainClient implements OpenBrainClientLike {
  private readonly baseUrl: string;
  private readonly apiKey: string;
  private readonly fetchImpl: typeof fetch;

  constructor(options: OpenBrainClientOptions) {
    this.baseUrl = normalizeBaseUrl(options.baseUrl);
    this.apiKey = normalizeApiKey(options.apiKey);
    this.fetchImpl = options.fetchImpl ?? fetch;
  }

  async createThought(input: OpenBrainThoughtInput): Promise<OpenBrainThought> {
    const payload = await this.request<unknown>("/v1/thoughts", {
      method: "POST",
      body: JSON.stringify(input),
    });
    return this.extractThought(payload);
  }

  async search(input: OpenBrainSearchInput): Promise<OpenBrainThought[]> {
    const payload = await this.request<unknown>("/v1/search", {
      method: "POST",
      body: JSON.stringify(input),
    });
    return this.extractThoughtArray(payload);
  }

  async listRecent(input: { limit: number; source?: string }): Promise<OpenBrainThought[]> {
    const params = new URLSearchParams({
      limit: String(input.limit),
    });

    if (input.source !== undefined && input.source.length > 0) {
      params.set("source", input.source);
    }

    const payload = await this.request<unknown>(`/v1/thoughts/recent?${params.toString()}`, {
      method: "GET",
    });

    return this.extractThoughtArray(payload);
  }

  async updateThought(
    id: string,
    payload: { content?: string; metadata?: OpenBrainThoughtMetadata },
  ): Promise<OpenBrainThought> {
    const responsePayload = await this.request<unknown>(`/v1/thoughts/${encodeURIComponent(id)}`, {
      method: "PATCH",
      body: JSON.stringify(payload),
    });

    return this.extractThought(responsePayload);
  }

  async deleteThought(id: string): Promise<void> {
    await this.request<unknown>(`/v1/thoughts/${encodeURIComponent(id)}`, {
      method: "DELETE",
    });
  }

  async deleteThoughts(params: { source?: string; metadataId?: string }): Promise<void> {
    const query = new URLSearchParams();
    if (params.source !== undefined && params.source.length > 0) {
      query.set("source", params.source);
    }
    if (params.metadataId !== undefined && params.metadataId.length > 0) {
      query.set("metadata_id", params.metadataId);
    }

    const suffix = query.size > 0 ? `?${query.toString()}` : "";
    await this.request<unknown>(`/v1/thoughts${suffix}`, {
      method: "DELETE",
    });
  }

  private async request<T>(endpoint: string, init: RequestInit): Promise<T> {
    const headers = normalizeHeaders(init.headers);
    headers.Authorization = `Bearer ${this.apiKey}`;

    if (init.body !== undefined && headers["Content-Type"] === undefined) {
      headers["Content-Type"] = "application/json";
    }

    const url = `${this.baseUrl}${endpoint}`;

    let response: Response;
    try {
      response = await this.fetchImpl(url, {
        ...init,
        headers,
      });
    } catch (error) {
      throw new OpenBrainRequestError({ endpoint, cause: error });
    }

    if (!response.ok) {
      throw new OpenBrainHttpError({
        endpoint,
        status: response.status,
        responseBody: await readResponseBody(response),
      });
    }

    if (response.status === 204) {
      return undefined as T;
    }

    const contentType = response.headers.get("content-type") ?? "";
    if (!contentType.toLowerCase().includes("application/json")) {
      return undefined as T;
    }

    return (await response.json()) as T;
  }

  private extractThoughtArray(payload: unknown): OpenBrainThought[] {
    if (Array.isArray(payload)) {
      return payload.map((item) => this.normalizeThought(item));
    }

    if (!isRecord(payload)) {
      return [];
    }

    const candidates = [payload.thoughts, payload.data, payload.results, payload.items];
    for (const candidate of candidates) {
      if (Array.isArray(candidate)) {
        return candidate.map((item) => this.normalizeThought(item));
      }
    }

    return [];
  }

  private extractThought(payload: unknown): OpenBrainThought {
    if (isRecord(payload)) {
      const nested = payload.thought;
      if (nested !== undefined) {
        return this.normalizeThought(nested);
      }

      const data = payload.data;
      if (data !== undefined && !Array.isArray(data)) {
        return this.normalizeThought(data);
      }
    }

    return this.normalizeThought(payload);
  }

  private normalizeThought(value: unknown): OpenBrainThought {
    if (!isRecord(value)) {
      return {
        id: "",
        content: "",
        source: "",
        metadata: undefined,
        createdAt: undefined,
        updatedAt: undefined,
        score: undefined,
      };
    }

    const metadataValue = value.metadata;
    const metadata = isRecord(metadataValue)
      ? ({ ...metadataValue } as OpenBrainThoughtMetadata)
      : undefined;

    const id = readString(value, "id") ?? readString(value, "thought_id") ?? "";
    const content =
      readString(value, "content") ??
      readString(value, "text") ??
      (value.content === undefined ? "" : String(value.content));
    const source = readString(value, "source") ?? "";

    const createdAt = readString(value, "createdAt") ?? readString(value, "created_at");
    const updatedAt = readString(value, "updatedAt") ?? readString(value, "updated_at");
    const score = readNumber(value, "score");

    return {
      ...value,
      id,
      content,
      source,
      metadata,
      createdAt,
      updatedAt,
      score,
    };
  }
}

export { normalizeApiKey, normalizeBaseUrl };