/**
 * No-thinking gateway model IDs (free-claude-code port, Fase 8.1).
 *
 * Some clients — most notably Claude Code — always attach a `thinking` block to
 * certain Claude models and offer no UI to turn it off. To let an operator force a
 * thinking-capable model into a no-thinking mode purely by *model selection*, the
 * gateway exposes a synthetic catalog id:
 *
 *     no-think/<provider>/<model>
 *
 * When such an id arrives on a request we strip the prefix back to the real
 * `<provider>/<model>` and suppress reasoning (`thinking:{type:"disabled"}` for the
 * Claude/Messages path; drop `reasoning`/`reasoning_effort` for the OpenAI path).
 * The existing `normalizeThinkingForModel()` still runs downstream, so models that
 * reject `disabled` are handled exactly as before.
 *
 * Catalog visibility is gated (see `shouldExposeNoThinkingAlias`): we only advertise
 * the variant for Claude-family models that actually support thinking AND honor
 * `disabled` — advertising it for a model that ignores suppression would be a lie.
 * An explicit registry override (`ModelSpec.noThinkingAlias`) wins over the default.
 */
import { getModelSpec } from "@/shared/constants/modelSpecs";

export const NO_THINKING_PREFIX = "no-think/";

/** True when `modelId` carries the no-thinking gateway prefix. */
export function isNoThinkingAlias(modelId: unknown): modelId is string {
  return typeof modelId === "string" && modelId.startsWith(NO_THINKING_PREFIX);
}

/** Remove the gateway prefix, returning the real `<provider>/<model>` (plain ids pass through). */
export function stripNoThinkingAlias(modelId: string): string {
  return isNoThinkingAlias(modelId) ? modelId.slice(NO_THINKING_PREFIX.length) : modelId;
}

/** Wrap a real qualified model id in the no-thinking gateway prefix. */
export function toNoThinkingAlias(qualifiedModelId: string): string {
  return `${NO_THINKING_PREFIX}${qualifiedModelId}`;
}

interface ApplyResult {
  applied: boolean;
  realModel?: string;
}

/**
 * Request-side hook: if `body.model` is a no-thinking alias, rewrite it to the real
 * model and suppress reasoning in place. No-op (and body untouched) otherwise.
 */
export function applyNoThinkingAlias(
  body: Record<string, unknown> | null | undefined,
  opts: { claudeFormat?: boolean } = {}
): ApplyResult {
  if (!body || typeof body !== "object") return { applied: false };
  const model = body.model;
  if (!isNoThinkingAlias(model)) return { applied: false };

  const realModel = stripNoThinkingAlias(model);
  if (!realModel) return { applied: false }; // malformed: nothing after the prefix

  body.model = realModel;
  if (opts.claudeFormat === true) {
    body.thinking = { type: "disabled" };
  }
  delete body.reasoning_effort;
  delete body.reasoning;
  return { applied: true, realModel };
}

interface CatalogModelEntry {
  id?: unknown;
  owned_by?: unknown;
  name?: unknown;
  [key: string]: unknown;
}

/** Strip a `<provider>/` prefix to get the bare model name for spec lookup. */
function bareModelName(id: string): string {
  const slash = id.lastIndexOf("/");
  return slash >= 0 ? id.slice(slash + 1) : id;
}

/**
 * Whether the catalog should advertise a no-thinking variant for this entry.
 *
 * Default rule: Claude-family model that supports thinking and does NOT reject
 * `thinking:{type:"disabled"}`. An explicit `ModelSpec.noThinkingAlias` boolean
 * overrides the default in either direction (operator opt-in / opt-out).
 */
export function shouldExposeNoThinkingAlias(model: CatalogModelEntry): boolean {
  if (!model || typeof model !== "object") return false;
  const id = model.id;
  if (typeof id !== "string" || id.length === 0) return false;
  if (model.owned_by === "combo") return false; // combos are virtual
  if (isNoThinkingAlias(id)) return false; // never double-alias

  const name = bareModelName(id);
  const spec = getModelSpec(name);
  if (!spec) return false;

  if (spec.noThinkingAlias === true) return true;
  if (spec.noThinkingAlias === false) return false;

  return (
    spec.supportsThinking === true && spec.rejectsThinkingDisabled !== true && /claude/i.test(name)
  );
}

/**
 * Normalize the provider prefix inside a qualified model id using an alias→canonical map.
 * e.g. "cc/claude-opus-4-6" → "claude/claude-opus-4-6" when aliasToCanonical["cc"]="claude".
 * Ids without a "/" or whose prefix is not in the map are returned unchanged.
 */
function normalizeProviderPrefix(
  qualifiedId: string,
  aliasToCanonical: Record<string, string>
): string {
  const slash = qualifiedId.indexOf("/");
  if (slash < 0) return qualifiedId;
  const prefix = qualifiedId.slice(0, slash);
  const canonical = aliasToCanonical[prefix];
  return canonical && canonical !== prefix
    ? `${canonical}${qualifiedId.slice(slash)}`
    : qualifiedId;
}

/**
 * Append a no-thinking variant for every eligible model. Returns the original array
 * reference unchanged when nothing is eligible (no allocation in the common case).
 *
 * @param aliasToCanonical - When provided, the inner provider prefix of each variant id is
 *   normalized to its canonical form (e.g. "cc" → "claude"). Pass this when the catalog is
 *   emitting canonical-prefixed ids so no-think variants stay consistent with the prefix mode.
 */
export function appendNoThinkingVariants<T extends CatalogModelEntry>(
  models: T[],
  aliasToCanonical?: Record<string, string>
): T[] {
  if (!Array.isArray(models)) return models;
  const variants: T[] = [];
  for (const model of models) {
    if (!shouldExposeNoThinkingAlias(model)) continue;
    const rawId = model.id as string;
    const qualifiedId = aliasToCanonical ? normalizeProviderPrefix(rawId, aliasToCanonical) : rawId;
    const aliasId = toNoThinkingAlias(qualifiedId);
    const variant: T = { ...model, id: aliasId, root: aliasId };
    if (typeof model.name === "string" && model.name) {
      variant.name = `${model.name} (no thinking)`;
    }
    variants.push(variant);
  }
  return variants.length > 0 ? [...models, ...variants] : models;
}