const { toSafeRedirectUrl } = require("./urlSafety")

const ALLOWED_DESCRIPTION_TAGS = new Set(["p", "strong", "ul", "ol", "li", "img", "br"])
const SELF_CLOSING_DESCRIPTION_TAGS = new Set(["img", "br"])

function stripControlChars(value) {
  return String(value || "").replace(/[\u0000-\u001F\u007F]/g, "")
}

function stripHtmlTags(value) {
  return String(value || "")
    .replace(/<!--[\s\S]*?-->/g, "")
    .replace(/<\/?[^>]+>/g, "")
}

function escapeHtml(value) {
  return String(value || "")
    .replace(/&/g, "&amp;")
    .replace(/</g, "&lt;")
    .replace(/>/g, "&gt;")
}

function escapeHtmlAttribute(value) {
  return String(value || "")
    .replace(/&/g, "&amp;")
    .replace(/"/g, "&quot;")
    .replace(/</g, "&lt;")
    .replace(/>/g, "&gt;")
}

function sanitizeOptionalPlainText(value, { maxLength } = {}) {
  if (value === undefined || value === null) return null

  let normalized = stripControlChars(value)
  normalized = stripHtmlTags(normalized).trim()
  if (!normalized) return null
  if (Number.isInteger(maxLength) && maxLength > 0 && normalized.length > maxLength) {
    normalized = normalized.slice(0, maxLength)
  }
  return normalized
}

function sanitizeRequiredPlainText(value, { fieldName = "field", maxLength } = {}) {
  const normalized = sanitizeOptionalPlainText(value, { maxLength })
  if (!normalized) {
    const err = new Error(`${fieldName}_REQUIRED`)
    err.statusCode = 400
    throw err
  }
  return normalized
}

function sanitizeImageSrc(value) {
  const trimmed = stripControlChars(value).trim()
  if (!trimmed) return null

  const lower = trimmed.toLowerCase()
  if (
    lower.startsWith("javascript:") ||
    lower.startsWith("data:") ||
    lower.startsWith("vbscript:")
  ) {
    return null
  }

  const isHttp = lower.startsWith("http://") || lower.startsWith("https://")
  const isProtocolRelative = lower.startsWith("//")
  const isRootRelative = trimmed.startsWith("/")
  if (!isHttp && !isProtocolRelative && !isRootRelative) return null

  return toSafeRedirectUrl(trimmed)
}

function sanitizeImgTagAttributes(rawAttrs = "") {
  const attrs = {}
  const attrRegex = /([a-zA-Z0-9:-]+)\s*=\s*("([^"]*)"|'([^']*)'|([^\s"'=<>`]+))/g
  let match

  while ((match = attrRegex.exec(rawAttrs)) !== null) {
    const name = String(match[1] || "").toLowerCase()
    const rawValue = match[3] ?? match[4] ?? match[5] ?? ""
    if (name === "src") {
      const safeSrc = sanitizeImageSrc(rawValue)
      if (safeSrc) attrs.src = safeSrc
      continue
    }
    if (name === "alt" || name === "title") {
      const safeText = sanitizeOptionalPlainText(rawValue, { maxLength: 300 })
      if (safeText) attrs[name] = safeText
    }
  }

  return attrs
}

function sanitizeDealDescriptionHtml(value) {
  if (value === undefined || value === null) return null

  const raw = stripControlChars(value).trim()
  if (!raw) return null

  const tagRegex =
    /<\/?([a-zA-Z0-9]+)((?:\s+[a-zA-Z0-9:-]+(?:\s*=\s*(?:"[^"]*"|'[^']*'|[^\s"'=<>`]+))?)*)\s*\/?>/g
  const stack = []
  let output = ""
  let cursor = 0
  let match

  while ((match = tagRegex.exec(raw)) !== null) {
    const [fullTag, rawTagName, rawAttrs = ""] = match
    const tagName = String(rawTagName || "").toLowerCase()
    const isClosing = fullTag.startsWith("</")

    output += escapeHtml(raw.slice(cursor, match.index))

    if (ALLOWED_DESCRIPTION_TAGS.has(tagName)) {
      if (isClosing) {
        if (!SELF_CLOSING_DESCRIPTION_TAGS.has(tagName)) {
          const idx = stack.lastIndexOf(tagName)
          if (idx !== -1) {
            for (let i = stack.length - 1; i >= idx; i -= 1) {
              output += `</${stack.pop()}>`
            }
          }
        }
      } else if (tagName === "br") {
        output += "<br>"
      } else if (tagName === "img") {
        const attrs = sanitizeImgTagAttributes(rawAttrs)
        if (attrs.src) {
          const altPart = attrs.alt ? ` alt="${escapeHtmlAttribute(attrs.alt)}"` : ""
          const titlePart = attrs.title ? ` title="${escapeHtmlAttribute(attrs.title)}"` : ""
          output += `<img src="${escapeHtmlAttribute(attrs.src)}"${altPart}${titlePart}>`
        }
      } else {
        output += `<${tagName}>`
        stack.push(tagName)
      }
    }

    cursor = tagRegex.lastIndex
  }

  output += escapeHtml(raw.slice(cursor))

  while (stack.length) {
    output += `</${stack.pop()}>`
  }

  const normalized = output.trim()
  return normalized || null
}

module.exports = {
  sanitizeOptionalPlainText,
  sanitizeRequiredPlainText,
  sanitizeDealDescriptionHtml,
}