import type { Context } from 'hono'

import type * as App from '../../App.js'
import type * as Db from '../../db/Db.js'
import * as FundingProvider from '../../internal/funding/Provider.js'

const sourceScopes = new WeakMap<Db.Source, number>()
let nextSourceScope = 0

/** Returns an inventory cache key scoped by request URL, providers, and database source. */
export function key(c: Context<App.Environment>) {
  const url = new URL(c.req.url)
  const providers = c
    .get('providers')
    .filter(FundingProvider.is)
    .map((provider) => provider.id)
    .sort()
  url.searchParams.set('__tempo_database', String(sourceScope(c.get('dbCached'))))
  url.searchParams.set('__tempo_providers', providers.join(','))
  return url.toString()
}

function sourceScope(source: Db.Source) {
  const current = sourceScopes.get(source)
  if (current !== undefined) return current
  // A production isolate has one source, while multi-app runtimes receive distinct scopes.
  const scope = nextSourceScope++
  sourceScopes.set(source, scope)
  return scope
}