import type { TreeStructure } from '@/types'

export interface TreeMetadata {
  name?: string
  description?: string
  category?: string
  tags?: string[]
}

/**
 * Lightweight frontend serializer for instant preview when switching Form→Code.
 * The backend remains authoritative for actual saves.
 */
export function treeStructureToMarkdownPreview(
  structure: TreeStructure,
  metadata?: TreeMetadata,
): string {
  const blocks: string[] = []

  if (metadata) {
    const fm = ['---']
    if (metadata.name) fm.push(`name: ${metadata.name}`)
    if (metadata.description) fm.push(`description: ${metadata.description}`)
    if (metadata.category) fm.push(`category: ${metadata.category}`)
    if (metadata.tags?.length) fm.push(`tags: [${metadata.tags.join(', ')}]`)
    fm.push('---')
    blocks.push(fm.join('\n'))
  }

  serializeNode(structure, null, blocks)
  return blocks.join('\n\n') + '\n'
}

function serializeNode(
  node: TreeStructure,
  parentId: string | null,
  blocks: string[],
): void {
  const fm = ['---', `id: ${node.id}`, `type: ${node.type}`]
  if (parentId !== null) fm.push(`parent: ${parentId}`)
  fm.push('---')

  const body: string[] = []

  if (node.type === 'decision') {
    if (node.question) {
      body.push(`# ${node.question}`, '')
    }
    if (node.help_text) {
      for (const line of node.help_text.split('\n')) {
        body.push(`> ${line}`)
      }
      body.push('')
    }
    if (node.options) {
      node.options.forEach((opt, i) => {
        const letter = String.fromCharCode(65 + i)
        if (opt.next_node_id) {
          body.push(`- [${letter}] ${opt.label} → @${opt.next_node_id}`)
        } else {
          body.push(`- [${letter}] ${opt.label}`)
        }
      })
    }
  } else if (node.type === 'action') {
    if (node.title) body.push(`## ${node.title}`, '')
    if (node.description) body.push(node.description, '')
    if (node.commands?.length) {
      body.push('```commands')
      node.commands.forEach(cmd => body.push(cmd))
      body.push('```', '')
    }
    if (node.expected_outcome) body.push(`**Expected:** ${node.expected_outcome}`, '')
    if (node.next_node_id) body.push(`→ @${node.next_node_id}`)
  } else if (node.type === 'solution') {
    if (node.title) body.push(`## ${node.title}`, '')
    if (node.description) body.push(node.description, '')
    if (node.resolution_steps?.length) {
      node.resolution_steps.forEach((step, i) => body.push(`${i + 1}. ${step}`))
    }
  }

  blocks.push(fm.join('\n') + '\n' + body.join('\n'))

  if (node.children) {
    for (const child of node.children) {
      serializeNode(child, node.id, blocks)
    }
  }
}