import type {
  DesignAsset,
  DesignSpecificationValues,
  DesignUserFieldOperation,
  DesignWorkspace,
} from '../../../shared/image-workspace';
import {
  insertReferenceToken,
  promptReferencesImage,
} from './reference-tokens';

type ReferenceValue = DesignSpecificationValues['references'][number];

function createReferenceId(): string {
  const random = globalThis.crypto?.randomUUID?.()
    ?? `${Date.now()}-${Math.random().toString(16).slice(2)}`;
  return `reference-${random}`.slice(0, 64);
}

export function creatorPromptForWorkspace(workspace: DesignWorkspace): string {
  const values = workspace.form.specification.values;
  return values.content.concept?.trim()
    || values.content.narrative?.trim()
    || [
      ...values.content.subjects.map((subject) => subject.description.trim()),
      values.content.action?.trim(),
      values.content.environment?.trim(),
      values.content.emotional_tone?.trim(),
    ].filter((value): value is string => Boolean(value)).join('，');
}

/**
 * Build the explicit field changes for using an existing image as a video's
 * first frame. The asset is only bound to the design; it is never copied or
 * deleted, and existing reference rows stay in place so @图片 numbers remain
 * stable.
 */
export function createVideoFirstFrameOperations(
  workspace: DesignWorkspace,
  asset: DesignAsset,
  promptOverride?: string,
): { operations: DesignUserFieldOperation[]; nextPrompt: string; referenceIndex: number } {
  if (asset.mediaType !== 'image') {
    throw new Error('视频开始画面必须使用图片');
  }

  const values = workspace.form.specification.values;
  const references = values.references;
  const currentFirstFrameIndex = references.findIndex((reference) => (
    reference.role === 'first_frame'
    || reference.asset_id === values.video.first_frame_asset_id
  ));
  const selectedReferenceIndex = references.findIndex((reference) => (
    reference.asset_id === asset.assetId
  ));

  let nextReferences: ReferenceValue[];
  let referenceIndex: number;
  if (selectedReferenceIndex >= 0) {
    referenceIndex = selectedReferenceIndex;
    nextReferences = references.map((reference, index) => {
      if (index === referenceIndex) return { ...reference, role: 'first_frame' };
      if (index === currentFirstFrameIndex && index !== referenceIndex) {
        return { ...reference, role: 'inspiration' };
      }
      return reference;
    });
  } else if (currentFirstFrameIndex >= 0) {
    referenceIndex = currentFirstFrameIndex;
    nextReferences = references.map((reference, index) => (
      index === referenceIndex
        ? { ...reference, asset_id: asset.assetId, asset_revision: null, role: 'first_frame' }
        : reference
    ));
  } else {
    referenceIndex = references.length;
    nextReferences = [
      ...references,
      {
        id: createReferenceId(),
        asset_id: asset.assetId,
        asset_revision: null,
        role: 'first_frame',
        preserve: [],
        adapt: [],
        do_not_copy: [],
        reviewed_observations: [],
      },
    ];
  }

  const prompt = promptOverride ?? creatorPromptForWorkspace(workspace);
  const inserted = promptReferencesImage(prompt, referenceIndex)
    ? { value: prompt }
    : insertReferenceToken(prompt, referenceIndex, null);
  const operations: DesignUserFieldOperation[] = [
    { kind: 'set', path: 'references', value: nextReferences },
    { kind: 'set', path: 'video.first_frame_asset_id', value: asset.assetId },
  ];
  if (inserted.value.trim() !== prompt.trim()) {
    operations.push({ kind: 'set', path: 'content.concept', value: inserted.value.trim() });
  }
  return { operations, nextPrompt: inserted.value.trim(), referenceIndex };
}