// server/supabase/functions/_shared/openai-embeddings.ts
// Embedding provider port + OpenAI adapter shared by embed-chunks and
// search-knowledge. The functions depend on the `EmbeddingProvider` port only,
// so the quota/size policy can be tested without the network.

export const EMBEDDING_MODEL = 'text-embedding-3-small'
export const EMBEDDING_DIMENSIONS = 1536
export const EMBEDDING_PROVIDER_TIMEOUT_MS = 45_000
const OPENAI_EMBEDDINGS_URL = 'https://api.openai.com/v1/embeddings'

export interface EmbeddingItem {
  embedding?: unknown
  index?: unknown
}

export type EmbeddingOutcome =
  | { ok: true; data: EmbeddingItem[] }
  /** `upstream`: transport error or non-2xx status. `invalid`: 2xx with an unusable body. */
  | { ok: false; reason: 'upstream' | 'invalid' }

export interface EmbeddingProvider {
  embed(input: string | readonly string[]): Promise<EmbeddingOutcome>
}

export function isEmbedding(value: unknown): value is number[] {
  return Array.isArray(value)
    && value.length === EMBEDDING_DIMENSIONS
    && value.every((entry) => typeof entry === 'number' && Number.isFinite(entry))
}

export function createOpenAIEmbeddingProvider(
  apiKey: string,
  fetchImpl: typeof fetch = fetch,
): EmbeddingProvider {
  return {
    async embed(input) {
      let response: Response
      try {
        response = await fetchImpl(OPENAI_EMBEDDINGS_URL, {
          method: 'POST',
          headers: {
            Authorization: `Bearer ${apiKey}`,
            'Content-Type': 'application/json',
          },
          body: JSON.stringify({
            model: EMBEDDING_MODEL,
            input,
            dimensions: EMBEDDING_DIMENSIONS,
          }),
          signal: AbortSignal.timeout(EMBEDDING_PROVIDER_TIMEOUT_MS),
        })
      } catch {
        return { ok: false, reason: 'upstream' }
      }
      if (!response.ok) return { ok: false, reason: 'upstream' }
      const payload = await response.json().catch(() => null) as { data?: unknown } | null
      if (!payload || !Array.isArray(payload.data)) return { ok: false, reason: 'invalid' }
      return { ok: true, data: payload.data as EmbeddingItem[] }
    },
  }
}