import type { SkillFrontmatterSummary } from './skills'

type FrontmatterValue = string | string[]

function stripQuotePair(value: string): string {
  const trimmed = value.trim()
  if (
    (trimmed.startsWith('"') && trimmed.endsWith('"')) ||
    (trimmed.startsWith("'") && trimmed.endsWith("'"))
  ) {
    return trimmed.slice(1, -1)
  }
  return trimmed
}

function parseYamlFrontmatter(raw: string): Record<string, FrontmatterValue> {
  const lines = raw.replace(/\r\n/g, '\n').split('\n')
  const data: Record<string, FrontmatterValue> = {}
  let index = 0
  while (index < lines.length) {
    const line = lines[index]
    const match = /^([A-Za-z0-9_-]+):\s*(.*)$/.exec(line)
    if (!match) {
      index += 1
      continue
    }

    const key = match[1]
    const value = match[2].trim()
    if (value === '|' || value === '|-' || value === '>' || value === '>-') {
      const block: string[] = []
      index += 1
      while (index < lines.length && /^(?:\s{2,}|\s*$)/.test(lines[index])) {
        block.push(lines[index].replace(/^\s{2}/, ''))
        index += 1
      }
      data[key] = block
        .join(value.startsWith('>') ? ' ' : '\n')
        .replace(/\s+/g, ' ')
        .trim()
      continue
    }

    if (value === '') {
      const items: string[] = []
      index += 1
      while (index < lines.length) {
        const itemMatch = /^\s*-\s*(.+)$/.exec(lines[index])
        if (!itemMatch) {
          break
        }
        items.push(stripQuotePair(itemMatch[1]))
        index += 1
      }
      if (items.length > 0) {
        data[key] = items
        continue
      }
      data[key] = ''
      continue
    }

    data[key] = stripQuotePair(value)
    index += 1
  }
  return data
}

function firstHeading(body: string): string | null {
  const match = /^#\s+(.+)$/m.exec(body)
  return match?.[1].trim() || null
}

function firstParagraph(body: string): string | null {
  const lines = body.replace(/\r\n/g, '\n').split('\n')
  const paragraph: string[] = []
  for (const line of lines) {
    const trimmed = line.trim()
    if (!trimmed || trimmed.startsWith('#') || trimmed.startsWith('```')) {
      if (paragraph.length > 0) {
        break
      }
      continue
    }
    paragraph.push(trimmed)
    if (paragraph.join(' ').length > 240) {
      break
    }
  }
  return paragraph.length > 0 ? paragraph.join(' ') : null
}

export function summarizeSkillMarkdown(markdown: string): SkillFrontmatterSummary {
  const normalized = markdown.replace(/^\uFEFF/, '')
  const frontmatterMatch = /^---\s*\n([\s\S]*?)\n---\s*(?:\n|$)/.exec(normalized)
  const body = frontmatterMatch ? normalized.slice(frontmatterMatch[0].length) : normalized
  const frontmatter = frontmatterMatch ? parseYamlFrontmatter(frontmatterMatch[1]) : {}
  const nameValue = frontmatter.name
  const descriptionValue = frontmatter.description
  const name =
    typeof nameValue === 'string' && nameValue.trim() ? nameValue.trim() : firstHeading(body)
  const description =
    typeof descriptionValue === 'string' && descriptionValue.trim()
      ? descriptionValue.trim()
      : firstParagraph(body)
  return {
    name: name || null,
    description: description || null
  }
}