// deno-lint-ignore no-import-prefix
import { createClient } from 'https://esm.sh/@supabase/supabase-js@2.39.7'
import { corsHeaders, handleCorsPreflightRequest } from '../_shared/cors.ts'
import { requireUser, authErrorResponse, type AuthError } from '../_shared/auth.ts'

const EMBEDDING_DIMENSIONS = 1536
const PROVIDER_TIMEOUT_MS = 45_000

function json(status: number, body: Record<string, unknown>): Response {
  return new Response(JSON.stringify(body), {
    status,
    headers: { ...corsHeaders, 'Content-Type': 'application/json' },
  })
}

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

Deno.serve(async (req: Request) => {
  const preflight = handleCorsPreflightRequest(req)
  if (preflight) return preflight
  if (req.method !== 'POST') return json(405, { error: 'method_not_allowed' })

  try {
    await requireUser(req)
    const body = await req.json().catch(() => null) as {
      query?: unknown
      count?: unknown
    } | null
    const query = typeof body?.query === 'string' ? body.query.trim() : ''
    const count = body?.count === undefined ? 5 : body.count
    if (!query || query.length > 4_000) return json(400, { error: 'invalid_query' })
    if (typeof count !== 'number' || !Number.isInteger(count) || count < 1 || count > 20) {
      return json(400, { error: 'invalid_count' })
    }

    const openaiKey = Deno.env.get('OPENAI_API_KEY') ?? ''
    if (!openaiKey) return json(503, { error: 'embedding_provider_unavailable' })

    let embeddingResponse: Response
    try {
      embeddingResponse = await fetch('https://api.openai.com/v1/embeddings', {
        method: 'POST',
        headers: {
          Authorization: `Bearer ${openaiKey}`,
          'Content-Type': 'application/json',
        },
        body: JSON.stringify({
          model: 'text-embedding-3-small',
          input: query,
          dimensions: EMBEDDING_DIMENSIONS,
        }),
        signal: AbortSignal.timeout(PROVIDER_TIMEOUT_MS),
      })
    } catch {
      return json(502, { error: 'embedding_upstream_failed' })
    }
    if (!embeddingResponse.ok) return json(502, { error: 'embedding_upstream_failed' })

    const embeddingPayload = await embeddingResponse.json().catch(() => null) as {
      data?: Array<{ embedding?: unknown }>
    } | null
    const queryEmbedding = embeddingPayload?.data?.[0]?.embedding
    if (!isEmbedding(queryEmbedding)) return json(502, { error: 'embedding_response_invalid' })

    const authHeader = req.headers.get('Authorization') ?? ''
    const supabaseUrl = Deno.env.get('SUPABASE_URL') ?? ''
    const anonKey = Deno.env.get('SUPABASE_ANON_KEY') ?? ''
    if (!supabaseUrl || !anonKey) return json(503, { error: 'knowledge_storage_unavailable' })

    const userClient = createClient(supabaseUrl, anonKey, {
      global: { headers: { Authorization: authHeader } },
      auth: { persistSession: false, autoRefreshToken: false },
    })
    const result = await userClient.rpc('match_knowledge_chunks', {
      query_embedding: queryEmbedding,
      match_count: count,
      similarity_threshold: 0.5,
    })
    if (result.error) return json(500, { error: 'knowledge_search_failed' })

    return json(200, { results: result.data ?? [] })
  } catch (error) {
    if (
      error
      && typeof error === 'object'
      && 'status' in error
      && (error.status === 401 || error.status === 403)
      && 'message' in error
      && typeof error.message === 'string'
    ) {
      return authErrorResponse(error as AuthError, corsHeaders)
    }
    return json(500, { error: 'internal_error' })
  }
})