export const DETAIL_KIMI_THINKING_HEADER = "x-detail-agent-kimi-thinking";
export const DETAIL_KIMI_PROFILE_HEADER = "x-detail-agent-kimi-profile";

export type DetailKimiThinkingMode = "enabled" | "disabled";
export type DetailKimiPurpose = "plan" | "preflight" | "review" | "repair";

export type DetailKimiGenerateOptions = {
  temperature?: number;
  topP?: number;
  maxTokens?: number;
  headers?: Record<string, string>;
};

const KIMI_K26_PATTERN = /^kimi[-_.]?k2\.6(?:\b|[-_.])/i;
const MOONSHOT_BASE_URL_PATTERN = /moonshot\.(?:cn|ai)|kimi\.com/i;

export function isKimiK26ModelId(value: unknown) {
  return KIMI_K26_PATTERN.test(String(value || "").trim());
}

export function isMoonshotOfficialBaseUrl(value: unknown) {
  return MOONSHOT_BASE_URL_PATTERN.test(String(value || "").trim());
}

function normalizeThinkingMode(value: unknown): DetailKimiThinkingMode | null {
  const normalized = String(value || "").trim().toLowerCase();
  if (normalized === "enabled" || normalized === "on" || normalized === "true") {
    return "enabled";
  }
  if (normalized === "disabled" || normalized === "off" || normalized === "false") {
    return "disabled";
  }
  return null;
}

function getPurposeThinkingMode(purpose: DetailKimiPurpose): DetailKimiThinkingMode {
  if (purpose === "plan" || purpose === "repair") return "enabled";
  return "disabled";
}

function getPurposeMaxTokens(params: {
  purpose: DetailKimiPurpose;
  generationMode?: string | null;
}) {
  if (params.purpose === "plan") {
    return params.generationMode === "agent_layout" ? 16_000 : 10_000;
  }
  if (params.purpose === "repair") return 8_000;
  if (params.purpose === "preflight") return 4_096;
  return 3_000;
}

export function shouldUseKimiDetailProfile(params: {
  modelId?: string | null;
  providerBaseUrl?: string | null;
  isLocalMoonshot?: boolean;
}) {
  if (!isKimiK26ModelId(params.modelId)) return false;
  return Boolean(params.isLocalMoonshot) || isMoonshotOfficialBaseUrl(params.providerBaseUrl);
}

export function buildDetailKimiGenerateOptions(params: {
  purpose: DetailKimiPurpose;
  generationMode?: string | null;
  modelId?: string | null;
  providerBaseUrl?: string | null;
  isLocalMoonshot?: boolean;
}): DetailKimiGenerateOptions {
  if (!shouldUseKimiDetailProfile(params)) return {};

  const thinking = getPurposeThinkingMode(params.purpose);

  return {
    temperature: thinking === "enabled" ? 1 : 0.6,
    topP: 0.95,
    maxTokens: getPurposeMaxTokens(params),
    headers: {
      [DETAIL_KIMI_THINKING_HEADER]: thinking,
      [DETAIL_KIMI_PROFILE_HEADER]: `detail-ui-${params.purpose}`,
    },
  };
}

function toHeaders(headers: HeadersInit | undefined) {
  const next = new Headers();
  if (!headers) return next;

  if (headers instanceof Headers) {
    headers.forEach((value, key) => next.set(key, value));
    return next;
  }

  if (Array.isArray(headers)) {
    headers.forEach(([key, value]) => {
      if (value !== undefined && value !== null) next.set(key, String(value));
    });
    return next;
  }

  Object.entries(headers).forEach(([key, value]) => {
    if (value !== undefined && value !== null) next.set(key, String(value));
  });
  return next;
}

function bodyToString(body: BodyInit | null | undefined) {
  if (!body) return null;
  if (typeof body === "string") return body;
  if (body instanceof Uint8Array) {
    return new TextDecoder().decode(body);
  }
  return null;
}

function applyKimiThinkingToBody(params: {
  rawBody: string;
  thinking: DetailKimiThinkingMode | null;
}) {
  if (!params.thinking) return null;

  try {
    const body = JSON.parse(params.rawBody) as Record<string, unknown>;
    if (!isKimiK26ModelId(body.model)) return null;

    return JSON.stringify({
      ...body,
      thinking: { type: params.thinking },
    });
  } catch {
    return null;
  }
}

export function createMoonshotKimiFetch(baseFetch: typeof fetch = fetch): typeof fetch {
  return async (input, init) => {
    const headers = toHeaders(
      init?.headers || (input instanceof Request ? input.headers : undefined)
    );
    const thinking = normalizeThinkingMode(headers.get(DETAIL_KIMI_THINKING_HEADER));
    headers.delete(DETAIL_KIMI_THINKING_HEADER);
    headers.delete(DETAIL_KIMI_PROFILE_HEADER);

    const rawBody = bodyToString(init?.body);
    const patchedBody = rawBody ? applyKimiThinkingToBody({ rawBody, thinking }) : null;

    return baseFetch(input, {
      ...init,
      headers,
      body: patchedBody || init?.body,
    });
  };
}