import type { PickerAdapter, PickerNode } from '../../types/filePicker'
import { pickerFormat } from './validation'

/** Construct metadata only: no FileReader, arrayBuffer or upload. */
export function localFilesAdapter(
  files: File[],
  relativePaths?: (string | undefined)[],
): PickerAdapter {
  const nodes = new Map<string, PickerNode>()
  for (const [index, file] of files.entries()) {
    const relative = relativePaths?.[index] || file.webkitRelativePath || file.name
    const parts = relative.split('/')
    let parent: string | null = null
    for (let i = 0; i < parts.length - 1; i++) {
      const path = parts.slice(0, i + 1).join('/')
      if (!nodes.has(path))
        nodes.set(path, {
          kind: 'folder', name: parts[i]!, path, parentPath: parent,
          fileCount: 0, bytes: 0, formats: {},
        })
      parent = path
    }
    // Plain file picks can have equal names; preserve both File objects.
    let path = relative
    for (let n = 2; nodes.has(path); n++) path = `${relative} (${n})`
    nodes.set(path, {
      kind: 'file',
      name: file.name,
      path,
      parentPath: parent,
      bytes: file.size,
      modifiedAt: new Date(file.lastModified).toISOString(),
      format: pickerFormat(file.name),
      file,
    })
  }
  const children = new Map<string, PickerNode[]>()
  for (const node of nodes.values()) {
    const parent = node.parentPath ?? ''
    const siblings = children.get(parent)
    if (siblings) siblings.push(node)
    else children.set(parent, [node])
    if (node.kind !== 'file') continue
    // Each file contributes once to its ancestors, rather than scanning all
    // files again for every folder in the selection.
    for (let slash = node.path.indexOf('/'); slash >= 0; slash = node.path.indexOf('/', slash + 1)) {
      const folder = nodes.get(node.path.slice(0, slash))
      if (folder?.kind !== 'folder') continue
      folder.fileCount = (folder.fileCount ?? 0) + 1
      folder.bytes = (folder.bytes ?? 0) + (node.bytes ?? 0)
      folder.formats![node.format] = (folder.formats![node.format] ?? 0) + 1
    }
  }
  const list = (path: string) => [...(children.get(path) ?? [])]
  return {
    listRoot: async () => list(''),
    listChildren: async (path) => list(path),
    search: async (query, scope) =>
      [...nodes.values()].filter((node) => {
        const inScope = scope.recursive
          ? !scope.path || node.path.startsWith(`${scope.path}/`)
          : (node.parentPath ?? '') === scope.path
        return inScope && node.name.toLowerCase().includes(query.toLowerCase())
      }),
  }
}