import https from 'https'
import querystring from 'querystring'

export interface GrammarMatch {
  offset: number
  length: number
  message: string
  shortMessage: string
  replacement: string | null
  ruleId: string
  categoryId: string
}

const IGNORED_RULE_IDS = new Set([
  'WHITESPACE_RULE',
  'UNPAIRED_BRACKETS',
  'EN_QUOTES',
  'DASH_RULE',
  'WORD_CONTAINS_UNDERSCORE',
])

export async function checkGrammar(text: string, language = 'en-US'): Promise<GrammarMatch[]> {
  return new Promise((resolve, reject) => {
    const body = querystring.stringify({ text, language, enabledOnly: 'false' })
    const req = https.request(
      {
        hostname: 'api.languagetool.org',
        path: '/v2/check',
        method: 'POST',
        headers: {
          'Content-Type': 'application/x-www-form-urlencoded',
          'Content-Length': Buffer.byteLength(body),
          'Accept': 'application/json',
        },
      },
      (res) => {
        let data = ''
        res.on('data', (chunk) => { data += chunk })
        res.on('end', () => {
          try {
            const parsed = JSON.parse(data) as {
              matches: Array<{
                offset: number
                length: number
                message: string
                shortMessage: string
                replacements: Array<{ value: string }>
                rule: { id: string; category: { id: string } }
              }>
            }
            const matches: GrammarMatch[] = parsed.matches
              .filter((m) => !IGNORED_RULE_IDS.has(m.rule.id))
              .map((m) => ({
                offset: m.offset,
                length: m.length,
                message: m.message,
                shortMessage: m.shortMessage || m.message,
                replacement: m.replacements[0]?.value ?? null,
                ruleId: m.rule.id,
                categoryId: m.rule.category.id,
              }))
            resolve(matches)
          } catch (e) {
            reject(new Error(`LanguageTool parse error: ${String(e)}`))
          }
        })
      }
    )
    req.on('error', reject)
    req.setTimeout(15000, () => { req.destroy(); reject(new Error('Grammar check timed out')) })
    req.write(body)
    req.end()
  })
}