export type ExtensionCompatibilityKind = 'pi' | 'opencode' | 'unknown'
export type ExtensionCompatibilityStatus = 'supported' | 'partial' | 'unsupported'
export type ExtensionCompatibilityCapability = 'extensions' | 'skills' | 'prompts' | 'themes' | 'commands'

export interface ExtensionCompatibilityDescriptor {
  kind: ExtensionCompatibilityKind
  status: ExtensionCompatibilityStatus
  reason: string
  capabilities: ExtensionCompatibilityCapability[]
}

interface ExtensionPackageManifest {
  name?: unknown
  pi?: unknown
  opencode?: unknown
}

const PI_CAPABILITY_KEYS: ExtensionCompatibilityCapability[] = ['extensions', 'skills', 'prompts', 'themes']
const OPENCODE_CAPABILITY_KEYS: ExtensionCompatibilityCapability[] = ['extensions', 'commands']

export function describeExtensionCompatibility(manifest: ExtensionPackageManifest): ExtensionCompatibilityDescriptor {
  const piCapabilities = collectCapabilities(manifest.pi, PI_CAPABILITY_KEYS)
  if (piCapabilities.length > 0) {
    return {
      kind: 'pi',
      status: 'supported',
      reason: 'Package declares Pi extension entrypoints.',
      capabilities: piCapabilities,
    }
  }

  const opencodeCapabilities = collectCapabilities(manifest.opencode, OPENCODE_CAPABILITY_KEYS)
  if (opencodeCapabilities.length > 0) {
    return {
      kind: 'opencode',
      status: 'partial',
      reason: 'OpenCode manifest detected; execution is disabled until sandbox permissions are implemented.',
      capabilities: opencodeCapabilities,
    }
  }

  return {
    kind: 'unknown',
    status: 'unsupported',
    reason: 'No Pi or OpenCode extension manifest was detected.',
    capabilities: [],
  }
}

function collectCapabilities(
  value: unknown,
  capabilityKeys: ExtensionCompatibilityCapability[],
): ExtensionCompatibilityCapability[] {
  if (!isRecord(value)) return []
  return capabilityKeys.filter(key => hasManifestEntries(value[key]))
}

function hasManifestEntries(value: unknown): boolean {
  if (typeof value === 'string') return value.trim().length > 0
  if (Array.isArray(value)) return value.some(entry => typeof entry === 'string' && entry.trim().length > 0)
  return false
}

function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === 'object' && value !== null && !Array.isArray(value)
}