import type { PiModelProfile, PiModelProfiles } from "./pi-profiles.ts";
import type { ProviderModelConfigLike } from "./types.ts";

export interface ModelApiContext {
  availableModelId: string;
  metadataModelId?: string;
}

const GPT_5_5_MODEL = /^gpt-5\.5(?:-|$)/;
const GPT_5_6_MODEL = /^gpt-5\.6(?:-|$)/;
const GPT_6_MODEL = /^gpt-6(?:\.\d+)?(?:-|$)/;
const CLAUDE_MODEL = /^claude(?:-|$)/;

/** A model id without any owner or routing prefix (`plus/gpt-5.6-sol` -> `gpt-5.6-sol`). */
export function modelName(id: string): string {
  return id.slice(id.lastIndexOf("/") + 1);
}

function matchesModelId(context: ModelApiContext, pattern: RegExp): boolean {
  const ids = [context.availableModelId, context.metadataModelId].filter((id): id is string => id !== undefined);
  return ids.some((id) => pattern.test(modelName(id)));
}

export function isGpt55Model(context: ModelApiContext): boolean {
  return matchesModelId(context, GPT_5_5_MODEL);
}

export function isGpt56Model(context: ModelApiContext): boolean {
  return matchesModelId(context, GPT_5_6_MODEL);
}

/** GPT-6 family (`gpt-6-astra`, and any `gpt-6.x-*` successor). */
export function isGpt6Model(context: ModelApiContext): boolean {
  return matchesModelId(context, GPT_6_MODEL);
}

/**
 * The Codex Responses family: every GPT model CLIProxyAPI serves from a Codex
 * OAuth credential rather than a plain OpenAI API key. They share the same
 * Responses-only upstream, the same usage shape, and the same conservative
 * 272000 fallback context window when CPA publishes none for the route.
 *
 * Membership is pi's own `openai-codex` catalog when one is supplied. The
 * GPT-5.5/5.6/6 patterns cover models newer than the running pi and models a
 * later pi drops from its catalog (0.87 dropped GPT-5.4), which would otherwise
 * fall back to Chat Completions with the models.dev window.
 */
export function isCodexResponsesModel(context: ModelApiContext, profiles?: PiModelProfiles): boolean {
  return isGpt55Model(context)
    || isGpt56Model(context)
    || isGpt6Model(context)
    || profiles?.find("openai-codex", context) !== undefined;
}

export function isClaudeModel(context: ModelApiContext): boolean {
  return matchesModelId(context, CLAUDE_MODEL);
}

export interface ModelWire {
  /** Model-level API override; undefined keeps the provider default. */
  api?: ProviderModelConfigLike["api"];
  codexResponses: boolean;
  /** Pi's native definition of the model on the upstream CPA fronts for it, when pi knows it. */
  profile?: PiModelProfile;
}

/**
 * Select a model-level API when a mixed CLIProxyAPI catalog cannot share the
 * provider default, together with pi's native profile for that upstream.
 *
 * - Codex Responses models (see {@link isCodexResponsesModel}) use the
 *   Responses API so Pi receives the Responses usage shape needed for
 *   token-cost accounting. CLIProxyAPI serves these from Codex OAuth
 *   credentials, whose upstream is Responses-only.
 * - Claude models use the Anthropic Messages API, which CLIProxyAPI serves
 *   faithfully at `/v1/messages`. The Chat Completions shape cannot represent
 *   signed thinking blocks or per-turn thinking effort, so routing Claude
 *   through it drops signatures and breaks multi-turn reasoning replay.
 */
export function resolveModelWire(context: ModelApiContext, profiles?: PiModelProfiles): ModelWire {
  if (isClaudeModel(context)) {
    return { api: "anthropic-messages", codexResponses: false, profile: profiles?.find("anthropic", context) };
  }
  if (isCodexResponsesModel(context, profiles)) {
    return { api: "openai-responses", codexResponses: true, profile: profiles?.find("openai-codex", context) };
  }
  return { codexResponses: false };
}