import { readdirSync, statSync, readFileSync } from "node:fs"
import { join } from "node:path"

export type TemplateVariable = {
  path: string
  type: string
}

const IF_RE = /<@(?:if|elseif)\((.+?)\)>/g
const VAR_RE = /<@var\(context\.(.+?)(?::(\w+))?\)>/g
const EQ_RE = /^eq\(context\.(.+?),\s*"(.*)"\)$/
const PATH_RE = /^context\.(.+)$/

function extractCondition(expr: string, vars: TemplateVariable[]) {
  const eqMatch = expr.match(EQ_RE)
  if (eqMatch) {
    vars.push({ path: eqMatch[1]!, type: "string" })
    return
  }
  const pathMatch = expr.match(PATH_RE)
  if (pathMatch) {
    vars.push({ path: pathMatch[1]!, type: "boolean" })
  }
}

function extractFromString(text: string, vars: TemplateVariable[]) {
  for (const match of text.matchAll(IF_RE)) {
    extractCondition(match[1]!, vars)
  }
  for (const match of text.matchAll(VAR_RE)) {
    vars.push({ path: match[1]!, type: match[2] ?? "string" })
  }
}

function walkDir(dirPath: string, vars: TemplateVariable[]) {
  const entries = readdirSync(dirPath).sort()
  for (const entry of entries) {
    const fullPath = join(dirPath, entry)
    extractFromString(entry, vars)

    const stat = statSync(fullPath)
    if (stat.isDirectory()) {
      walkDir(fullPath, vars)
    } else if (stat.isFile()) {
      const content = readFileSync(fullPath, "utf-8")
      extractFromString(content, vars)
    }
  }
}

export function parse(dirPath: string): TemplateVariable[] {
  const vars: TemplateVariable[] = []
  walkDir(dirPath, vars)
  const seen = new Set<string>()
  return vars.filter(v => {
    const key = `${v.path}:${v.type}`
    if (seen.has(key)) return false
    seen.add(key)
    return true
  })
}