/** Persona `thinking` config — the wire shapes and the panel's form mapping
 *  (design/01 §2.1; provider mapping in design/04 §3.2).
 *
 *  Kept out of lib/types.ts (which is at its size ceiling) and, more importantly,
 *  out of the panel component: the mapping is pure, so the tri-state rules are
 *  testable without a browser.
 *
 *  Two rules the read/write sides share:
 *  - **`showToUser` is tri-state all the way.** `null`/absent = 未配置 = keep the
 *    current behavior (thinking frames keep flowing); `true`/`false` = an explicit
 *    choice. Flattening "unset" onto `false` would silently turn display off.
 *  - **An all-unset block is omitted, not sent as zeros.** The write side reads an
 *    omitted `thinking` object as "keep the stored one", so a panel that ships
 *    defaults would wipe a hand-edited config.
 */

/** Read shape of the `thinking` block (`GET /api/v1/admin/personas`, v0.43). The
 *  key is absent entirely when the persona configures none. */
export interface PersonaThinking {
  budgetTokens: number;
  effort: string;
  /** `null` = 未配置（保持现行为）, `true`/`false` = 显式选择. */
  showToUser: boolean | null;
  mode: string;
}

/** Write shape (`POST`/`PUT /api/v1/admin/personas`). An omitted key = unset; an
 *  omitted whole object = keep the stored block. */
export interface PersonaThinkingRequest {
  budgetTokens?: number;
  effort?: string;
  showToUser?: boolean;
  mode?: string;
}

/** Explicit reasoning switch, matching the backend's `ThinkingMode` constants
 *  (`internal/persona/loader`). */
export const THINKING_MODES = ["default", "on", "off"] as const;

/** `reasoning_effort` values the model layer recognizes across the providers it
 *  maps (design/04 §3.2). The **effective whitelist still depends on the active
 *  provider** — OpenAI-compatible takes `none…max`; DeepSeek takes
 *  `none/low/high/max` and normalizes the aliases (`minimal→low`, `medium→high`,
 *  `xhigh→high`, `ultra→max`) — and only the backend can see which provider is in
 *  play, so this list drives a select, not a promise. `ultra` is listed because
 *  DeepSeek accepts it as an alias; on an OpenAI-compatible provider the backend
 *  drops it and WARNs. */
export const THINKING_EFFORTS = [
  "none",
  "minimal",
  "low",
  "medium",
  "high",
  "xhigh",
  "max",
  "ultra",
] as const;

/** Form state: everything is a string so a half-typed number never coerces to 0
 *  and the tri-state select has an explicit "unset" arm. */
export interface ThinkingDraft {
  budgetTokens: string;
  effort: string;
  showToUser: "unset" | "on" | "off";
  mode: "" | (typeof THINKING_MODES)[number];
}

export const EMPTY_THINKING_DRAFT: ThinkingDraft = {
  budgetTokens: "",
  effort: "",
  showToUser: "unset",
  mode: "",
};

/** Backfill the form from the read side. An absent block (and an unknown mode)
 *  yields the empty draft, which maps back to "omitted" — so opening a persona
 *  that configures no thinking and saving it changes nothing. */
export function thinkingDraftFrom(read: PersonaThinking | null | undefined): ThinkingDraft {
  if (!read) return EMPTY_THINKING_DRAFT;
  return {
    budgetTokens: read.budgetTokens ? String(read.budgetTokens) : "",
    effort: read.effort ?? "",
    showToUser: read.showToUser === true ? "on" : read.showToUser === false ? "off" : "unset",
    mode: (THINKING_MODES as readonly string[]).includes(read.mode)
      ? (read.mode as ThinkingDraft["mode"])
      : "",
  };
}

/** Input validation only — what the client can actually know. Non-negative
 *  integer budget, enumerations for mode/effort. Whether the provider really
 *  honors the value is the backend's call (it validates against the active
 *  provider's whitelist and WARNs when it drops one); the panel does not pretend
 *  to know that, so it does not block on it. Returns an error message, or null. */
export function thinkingValidationError(draft: ThinkingDraft): string | null {
  const budget = draft.budgetTokens.trim();
  if (budget !== "") {
    if (!/^\d+$/.test(budget)) return "思考预算必须是非负整数";
    if (Number(budget) > Number.MAX_SAFE_INTEGER) return "思考预算过大";
  }
  if (draft.mode !== "" && !(THINKING_MODES as readonly string[]).includes(draft.mode)) {
    return `思考开关取值非法：${draft.mode}（仅 default/on/off）`;
  }
  if (draft.effort !== "" && !(THINKING_EFFORTS as readonly string[]).includes(draft.effort)) {
    return `思考强度取值非法：${draft.effort}`;
  }
  return null;
}

/** Whether the form holds anything at all. An untouched form must not be sent:
 *  the write side treats an omitted `thinking` object as "keep the stored block". */
export function thinkingDraftIsEmpty(draft: ThinkingDraft): boolean {
  return (
    draft.budgetTokens.trim() === "" &&
    draft.effort === "" &&
    draft.mode === "" &&
    draft.showToUser === "unset"
  );
}

/** Map the form onto the request body. Returns `undefined` when nothing is
 *  configured — the caller then omits `thinking` entirely, preserving whatever is
 *  stored (write-side semantics, unchanged). `showToUser: "unset"` omits the key
 *  so it stays `nil` in the backend, never a flattened `false`. Callers validate
 *  with `thinkingValidationError` first. */
export function thinkingDraftToRequest(draft: ThinkingDraft): PersonaThinkingRequest | undefined {
  if (thinkingDraftIsEmpty(draft)) return undefined;
  const req: PersonaThinkingRequest = {};
  const budget = draft.budgetTokens.trim();
  if (budget !== "") req.budgetTokens = Number(budget);
  if (draft.effort !== "") req.effort = draft.effort;
  if (draft.mode !== "") req.mode = draft.mode;
  if (draft.showToUser !== "unset") req.showToUser = draft.showToUser === "on";
  return req;
}