/**
 * Anthropic Messages stream adapter for Bedrock Mantle. It rewrites Mantle
 * endpoints to Anthropic-compatible URLs and adjusts thinking-token budgets.
 */
import Anthropic from "@anthropic-ai/sdk";
import type { StreamFn } from "openclaw/plugin-sdk/agent-core";
import { stream, type Model, type SimpleStreamOptions } from "openclaw/plugin-sdk/llm";

const MANTLE_ANTHROPIC_BETA = "fine-grained-tool-streaming-2025-05-14";
type AnthropicOptions = ConstructorParameters<typeof Anthropic>[0];
type MantleAnthropicStream = typeof stream;

/** Resolve the Anthropic-compatible Mantle base URL from a provider base URL. */
export function resolveMantleAnthropicBaseUrl(baseUrl: string): string {
  const trimmed = baseUrl.replace(/\/+$/, "");
  if (trimmed.endsWith("/anthropic")) {
    return trimmed;
  }
  if (trimmed.endsWith("/v1")) {
    return `${trimmed.slice(0, -"/v1".length)}/anthropic`;
  }
  return `${trimmed}/anthropic`;
}

function requiresDefaultSampling(modelId: string): boolean {
  return modelId.includes("claude-opus-4-7");
}

function isClaudeMythosPreviewModel(model: Model): boolean {
  return [model.id, model.name, model.params?.canonicalModelId]
    .filter((value): value is string => typeof value === "string")
    .some((value) =>
      /(?:^|-)claude-mythos-preview(?=$|[^a-z0-9])/.test(
        value
          .trim()
          .toLowerCase()
          .replace(/[\s_.:]+/g, "-"),
      ),
    );
}

function resolveMantleReasoning(
  model: Model,
  options: SimpleStreamOptions | undefined,
): NonNullable<SimpleStreamOptions["reasoning"]> | undefined {
  if (requiresDefaultSampling(model.id)) {
    return undefined;
  }
  const reasoning = options?.reasoning ?? (isClaudeMythosPreviewModel(model) ? "high" : undefined);
  if (!isClaudeMythosPreviewModel(model)) {
    return reasoning;
  }
  if (reasoning === "minimal") {
    return "low";
  }
  return reasoning === "xhigh" || reasoning === "max" ? "high" : reasoning;
}

function mergeHeaders(
  ...headerSources: Array<Record<string, string> | undefined>
): Record<string, string> {
  const merged: Record<string, string> = {};
  for (const headers of headerSources) {
    if (headers) {
      Object.assign(merged, headers);
    }
  }
  return merged;
}

function buildMantleAnthropicBaseOptions(
  model: Model,
  options: SimpleStreamOptions | undefined,
  apiKey: string,
) {
  return {
    temperature: requiresDefaultSampling(model.id) ? undefined : options?.temperature,
    maxTokens: options?.maxTokens || Math.min(model.maxTokens, 32_000),
    signal: options?.signal,
    apiKey,
    cacheRetention: options?.cacheRetention,
    sessionId: options?.sessionId,
    onPayload: options?.onPayload,
    maxRetryDelayMs: options?.maxRetryDelayMs,
    metadata: options?.metadata,
  };
}

function adjustMaxTokensForThinking(
  baseMaxTokens: number,
  modelMaxTokens: number,
  reasoningLevel: NonNullable<SimpleStreamOptions["reasoning"]>,
  customBudgets?: SimpleStreamOptions["thinkingBudgets"],
): { maxTokens: number; thinkingBudget: number } {
  const defaultBudgets = {
    minimal: 1024,
    low: 2048,
    medium: 8192,
    high: 16384,
    xhigh: 16384,
    max: 16384,
  } as const;
  const budgets = { ...defaultBudgets, ...customBudgets };
  const minOutputTokens = 1024;
  let thinkingBudget = budgets[reasoningLevel];
  const maxTokens = Math.min(baseMaxTokens + thinkingBudget, modelMaxTokens);
  if (maxTokens <= thinkingBudget) {
    thinkingBudget = Math.max(0, maxTokens - minOutputTokens);
  }
  return { maxTokens, thinkingBudget };
}

/** Create the Mantle Anthropic Messages stream function. */
export function createMantleAnthropicStreamFn(deps?: {
  createClient?: (options: AnthropicOptions) => Anthropic;
  stream?: MantleAnthropicStream;
}): StreamFn {
  return (model, context, options) => {
    const apiKey = options?.apiKey ?? "";
    const createClient = deps?.createClient ?? ((clientOptions) => new Anthropic(clientOptions));
    const streamFn = deps?.stream ?? stream;
    const client = createClient({
      apiKey: null,
      authToken: apiKey,
      baseURL: resolveMantleAnthropicBaseUrl(model.baseUrl),
      dangerouslyAllowBrowser: true,
      defaultHeaders: mergeHeaders(
        {
          accept: "application/json",
          "anthropic-dangerous-direct-browser-access": "true",
          "anthropic-beta": MANTLE_ANTHROPIC_BETA,
        },
        model.headers,
        options?.headers,
      ),
    });
    const base = buildMantleAnthropicBaseOptions(model, options, apiKey);
    // Plugin package deps can give this plugin a distinct physical SDK copy.
    // The client API is the same, but the SDK class private field makes types nominal.
    const streamClient = client as unknown as Anthropic;
    const reasoning = resolveMantleReasoning(model, options);
    if (!reasoning) {
      return streamFn(model as Model<"anthropic-messages">, context, {
        ...base,
        client: streamClient,
        thinkingEnabled: false,
      });
    }

    const adjusted = adjustMaxTokensForThinking(
      base.maxTokens || 0,
      model.maxTokens,
      reasoning,
      options?.thinkingBudgets,
    );
    return streamFn(model as Model<"anthropic-messages">, context, {
      ...base,
      client: streamClient,
      maxTokens: adjusted.maxTokens,
      thinkingEnabled: true,
      ...(isClaudeMythosPreviewModel(model) ? { effort: reasoning } : {}),
      thinkingBudgetTokens: adjusted.thinkingBudget,
    });
  };
}