import { extractMaterialPlaceholders } from "@/lib/prompt/material-placeholders";

export type MaterialDraftKind = "image" | "video" | "audio";

const tokenBoundaryBeforePattern = /[\s，。；：、（(【\[]$/;
const tokenBoundaryAfterPattern = /^[\s，。；：、）)】\]]/;

export function detectMaterialDraftStart(previous: string, next: string, cursor: number): { text: string; index: number } | null {
  const index = cursor - 1;
  if (index < 0 || next[index] !== "@") return null;
  if (next.length !== previous.length + 1) return null;
  if (`${next.slice(0, index)}${next.slice(cursor)}` !== previous) return null;
  return { text: previous, index };
}

export function normalizeMaterialDraftToken(input: string, prompt: string, defaultKind: MaterialDraftKind = "image"): string | null {
  const query = input.replace(/^@+/, "").trim().replace(/\s+/g, "");
  if (!query) return nextMaterialDraftToken(defaultKind, prompt);

  const explicit = query.match(/^(参考视频|图片|图|视频|音频)(\d+)$/);
  if (explicit) {
    const kind = kindFromText(explicit[1]);
    const index = Number(explicit[2]);
    if (Number.isInteger(index) && index > 0) return labelForDraftKind(kind, index);
    return null;
  }

  const kindOnly = query.match(/^(参考视频|图片|图|视频|音频)$/);
  if (kindOnly) return nextMaterialDraftToken(kindFromText(kindOnly[1]), prompt);

  return null;
}

export function nextMaterialDraftToken(kind: MaterialDraftKind, prompt: string): string {
  const placeholders = extractMaterialPlaceholders(prompt).filter((placeholder) => placeholder.type === kind);
  const nextIndex = placeholders.reduce((max, placeholder) => Math.max(max, placeholder.index), 0) + 1;
  return labelForDraftKind(kind, nextIndex);
}

export function insertMaterialDraftToken(text: string, index: number, token: string): { text: string; cursor: number } {
  const safeIndex = Math.max(0, Math.min(index, text.length));
  const before = text.slice(0, safeIndex);
  const after = text.slice(safeIndex);
  const needsLeadingSpace = before.length > 0 && !tokenBoundaryBeforePattern.test(before);
  const needsTrailingSpace = after.length === 0 || !tokenBoundaryAfterPattern.test(after);
  const insertion = `${needsLeadingSpace ? " " : ""}${token}${needsTrailingSpace ? " " : ""}`;
  return {
    text: `${before}${insertion}${after}`,
    cursor: before.length + insertion.length
  };
}

export function labelForDraftKind(kind: MaterialDraftKind, index: number): string {
  if (kind === "video") return `@视频${index}`;
  if (kind === "audio") return `@音频${index}`;
  return `@图片${index}`;
}

function kindFromText(value: string): MaterialDraftKind {
  if (value === "视频" || value === "参考视频") return "video";
  if (value === "音频") return "audio";
  return "image";
}