Create standalone browser port of LTX Athena with authenticated native API transport

frontend/lib/multi-keyframe.ts

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+import { clampKeyframeStrength, DEFAULT_KEYFRAME_STRENGTH } from './keyframe-strength.ts'
+import { pickFreeFrameIndex } from './keyframe-timeline.ts'
+
+export {
+  clampKeyframeStrength,
+  DEFAULT_KEYFRAME_STRENGTH,
+  MISSING_KEYFRAME_STRENGTH,
+} from './keyframe-strength.ts'
+
+/** Local Distilled cap. Must match backend LOCAL_MULTI_KEYFRAME_MAX_COUNT. API stays 0. */
+export const LOCAL_MULTI_KEYFRAME_MAX_COUNT = 10
+
+export interface KeyframeItem {
+  id: string
+  path: string
+  frameIndex: number
+  strength: number
+}
+
+export function appendKeyframePaths(
+  keyframes: readonly KeyframeItem[],
+  paths: readonly string[],
+  lastFrame: number,
+  preferredFrame: number,
+  maxCount: number,
+  createId: () => string = () => crypto.randomUUID(),
+): KeyframeItem[] {
+  const next = [...keyframes]
+  for (const path of paths) {
+    if (next.length >= maxCount) break
+    const frameIndex = pickFreeFrameIndex(next, lastFrame, preferredFrame)
+    if (frameIndex === null) break
+    next.push({ id: createId(), path, frameIndex, strength: DEFAULT_KEYFRAME_STRENGTH })
+  }
+  return next
+}
+
+export function applyKeyframeImagePaths({
+  keyframes,
+  paths,
+  replaceId,
+  lastFrame,
+  preferredFrame,
+  maxCount,
+  createId,
+}: {
+  keyframes: readonly KeyframeItem[]
+  paths: readonly string[]
+  replaceId: string | null
+  lastFrame: number | null
+  preferredFrame: number
+  maxCount: number
+  createId?: () => string
+}): KeyframeItem[] {
+  if (paths.length === 0) return [...keyframes]
+
+  let next = [...keyframes]
+  let remaining = paths
+  if (replaceId) {
+    const [first, ...rest] = paths
+    next = next.map((keyframe) => (
+      keyframe.id === replaceId ? { ...keyframe, path: first } : keyframe
+    ))
+    remaining = rest
+  }
+
+  if (lastFrame === null || remaining.length === 0) return next
+  return appendKeyframePaths(
+    next,
+    remaining,
+    lastFrame,
+    preferredFrame,
+    maxCount,
+    createId,
+  )
+}
+
+export type PersistedKeyframe = {
+  path: string
+  frameIndex: number
+  strength: number
+}
+
+export function toPersistedKeyframes(
+  keyframes: readonly KeyframeItem[],
+): PersistedKeyframe[] {
+  return keyframes.map(({ path, frameIndex, strength }) => ({
+    path,
+    frameIndex,
+    strength: clampKeyframeStrength(strength),
+  }))
+}
+
+export function fromPersistedKeyframes(
+  keyframes: readonly { path: string; frameIndex: number; strength?: number }[],
+  createId: () => string = () => crypto.randomUUID(),
+): KeyframeItem[] {
+  return keyframes.map(({ path, frameIndex, strength }) => ({
+    id: createId(),
+    path,
+    frameIndex,
+    strength: clampKeyframeStrength(strength),
+  }))
+}
+
+export function videoGenerationModeFromInputs({
+  keyframes,
+  audioUrl,
+  imageUrl,
+}: {
+  keyframes?: readonly unknown[] | null
+  audioUrl?: string | null
+  imageUrl?: string | null
+}): 'multi-keyframe' | 'audio-to-video' | 'image-to-video' | 'text-to-video' {
+  if (keyframes && keyframes.length > 0) return 'multi-keyframe'
+  if (audioUrl) return 'audio-to-video'
+  if (imageUrl) return 'image-to-video'
+  return 'text-to-video'
+}
+
+export function toKeyframeInputs(
+  keyframes: readonly Pick<KeyframeItem, 'path' | 'frameIndex' | 'strength'>[],
+): { imagePath: string; frameIndex: number; strength: number }[] {
+  return keyframes.map(({ path, frameIndex, strength }) => ({
+    imagePath: path,
+    frameIndex,
+    strength: clampKeyframeStrength(strength),
+  }))
+}
+
+export function enhanceKeyframesPayload(
+  keyframes: readonly Pick<KeyframeItem, 'path' | 'frameIndex' | 'strength'>[],
+): { imagePath: string; frameIndex: number; strength: number }[] | undefined {
+  if (keyframes.length === 0) return undefined
+  return toKeyframeInputs([...keyframes].sort((a, b) => a.frameIndex - b.frameIndex))
+}