import { useDocument } from '@terrace/core'
import { createStringReader } from '@terrace/core/readers/js-string'

export async function parse(lines, rootSchema) {
  const doc = useDocument(createStringReader(lines))

  const levelTracker = []

  function createScope(level, line, schema = null) {
    levelTracker.length = level
    const entry = levelTracker[level] = {}
    entry.scope = [line, []]

    if (schema) {
      entry.schemas = Object.values(schema),
      entry.matchers = Object.keys(schema),
      entry.counts = Object.values(schema).map(e => e.count)
    }

    return entry.scope
  }

  createScope(0, 'root', rootSchema)

  // Simpler parsing logic, don't need to worry about schemas, matchers, or counts if no schema is specified.
  if (!rootSchema) {
    while (true) {
      // If doc.next() returns true we've ended the document.
      if (await doc.next()) break;
      const level = doc.level()
      // Determine parent for this scope.
      const parent = levelTracker[level].scope
      // If there's no parent, skip this line.
      if (!parent) continue

      // Create new scope
      const scope = createScope(level + 1, doc.line())
      // Add current scope to parent.
      parent[1].push(scope)
    }
  // Full parsing logic
  } else {
    while (true) {
      // If doc.next() returns true we've ended the document.
      if (await doc.next()) break;
      const level = doc.level()
      if (!levelTracker[level]) continue

      // Determine parent for this scope.
      const parent = levelTracker[level].scope
      const schemas = levelTracker[level].schemas
      const matchers = levelTracker[level].matchers
      const counts = levelTracker[level].counts

      // Match the head value, or '?' for unspecified lines.
      const matchIndex = matchers.findIndex(entry => entry === doc.head() || entry === '?')

      // Handle trailing blocks of text. TODO: Proper trailing.
      if (matchIndex === -1 && matchers.includes('? literal')) {
        parent[1].push(...(await doc.content(level)).map(e => [e]))
        continue
      } else if (matchIndex === -1) continue

      // Return if the match has already been "used up"
      if (counts[matchIndex] === 0) continue
      // "use up" one more match
      counts[matchIndex] -= 1

      const scopeSchema = schemas[matchIndex]
      // Create new scope
      const scope = createScope(level + 1, doc.line(), scopeSchema?.children)
      parent[1].push(scope)
    }
  }

  return levelTracker[0].scope
}