/** Prépare le HTML d'un mail pour affichage dans une iframe sandboxée. */

import { stripHiddenEmailHtml } from "@/lib/strip-hidden-email-html"
import { preprocessEmailHtmlForTheme } from "@/lib/email-preview-dark-styles"

const REMOTE_URL = /^https?:\/\//i
const PROTOCOL_RELATIVE = /^\/\//

export type ParsedEmailHtml = {
  headMarkup: string
  bodyHtml: string
  /** Uniquement si le mail définit explicitement <base href>. */
  documentBaseHref?: string
  /** Base pour résoudre les URLs relatives dans le HTML. */
  resolveBaseHref?: string
}

function escapeHtmlAttr(value: string): string {
  return value
    .replace(/&/g, "&amp;")
    .replace(/"/g, "&quot;")
    .replace(/</g, "&lt;")
}

export { escapeHtmlAttr }

function resolveUrl(url: string, baseHref?: string): string {
  const trimmed = url.trim()
  if (!trimmed || trimmed.startsWith("data:") || trimmed.startsWith("cid:")) {
    return trimmed
  }
  if (trimmed.startsWith("mailto:") || trimmed.startsWith("#")) return trimmed
  if (REMOTE_URL.test(trimmed)) {
    return trimmed.startsWith("http://")
      ? `https://${trimmed.slice("http://".length)}`
      : trimmed
  }
  if (PROTOCOL_RELATIVE.test(trimmed)) {
    return `https:${trimmed}`
  }
  if (!baseHref) return trimmed
  try {
    const resolved = new URL(trimmed, baseHref).href
    return resolved.startsWith("http://")
      ? `https://${resolved.slice("http://".length)}`
      : resolved
  } catch {
    return trimmed
  }
}

function isStylesheetLink(el: Element): boolean {
  if (el.tagName.toLowerCase() !== "link") return false
  const rel = (el.getAttribute("rel") ?? "").toLowerCase()
  const type = (el.getAttribute("type") ?? "").toLowerCase()
  return rel.includes("stylesheet") || type === "text/css"
}

const LAZY_IMG_SRC_ATTRS = [
  "data-src",
  "data-original",
  "data-lazy-src",
  "data-url",
  "data-href",
  "data-image",
  "originalsrc",
] as const

function firstLazyImageSrc(img: Element): string | null {
  for (const name of LAZY_IMG_SRC_ATTRS) {
    const value = img.getAttribute(name)?.trim()
    if (value) return value
  }
  return null
}

/** Known 1×1 / spacer filenames — not arbitrary URL substrings. */
function isPlaceholderImageSrc(src: string): boolean {
  const t = src.trim().toLowerCase()
  if (!t || t === "about:blank" || t === "#") return true
  if (t.startsWith("data:")) return false
  try {
    const path = new URL(t, "https://example.invalid/").pathname
    const file = path.split("/").pop() ?? ""
    return /^(?:spacer|blank|pixel|1x1|clear|dot|transparent|spacer\.gif)\.(?:gif|png|jpe?g|svg|webp)$/i.test(
      file
    )
  } catch {
    return /(?:^|\/)(?:spacer|blank|pixel|1x1)\.(?:gif|png|jpe?g)/i.test(t)
  }
}

function collectHeadResourceMarkup(
  doc: Document,
  resolveBaseHref?: string
): string {
  const parts: string[] = []
  const nodes = [
    ...doc.head.querySelectorAll("style, link[rel]"),
    ...doc.body.querySelectorAll("style, link[rel]"),
  ]

  for (const node of nodes) {
    const tag = node.tagName.toLowerCase()
    if (tag === "style") {
      parts.push(node.outerHTML)
      node.remove()
      continue
    }
    if (isStylesheetLink(node)) {
      const href = node.getAttribute("href")
      if (href && resolveBaseHref) {
        node.setAttribute("href", resolveUrl(href, resolveBaseHref))
      }
      parts.push(node.outerHTML)
      node.remove()
    }
  }

  return parts.join("\n")
}

export function inferEmailResolveBaseHref(html: string): string | undefined {
  const baseMatch = html.match(/<base[^>]+href=["']([^"']+)["']/i)
  if (baseMatch?.[1]) {
    try {
      return new URL(baseMatch[1]).href
    } catch {
      return baseMatch[1]
    }
  }

  const stylesheetMatch = html.match(
    /<link[^>]+rel=["'][^"']*stylesheet[^"']*["'][^>]+href=["']([^"']+)["']/i
  ) ?? html.match(
    /<link[^>]+href=["']([^"']+)["'][^>]+rel=["'][^"']*stylesheet/i
  )
  if (stylesheetMatch?.[1]) {
    try {
      const u = new URL(stylesheetMatch[1], "https://example.com/")
      if (stylesheetMatch[1].startsWith("http") || stylesheetMatch[1].startsWith("//")) {
        return `${u.origin}${u.pathname.replace(/\/[^/]*$/, "/")}`
      }
    } catch {
      /* ignore */
    }
  }

  const absoluteMatch = html.match(
    /(?:src|href)=["'](https?:\/\/[^/"']+)[^"']*["']/i
  )
  if (absoluteMatch?.[1]) {
    try {
      const u = new URL(absoluteMatch[1])
      return `${u.origin}/`
    } catch {
      /* ignore */
    }
  }

  return undefined
}

/** Extrait styles/CSS + body d'un document HTML complet ou fragment. */
export function parseEmailHtmlForIframe(
  html: string,
  resolveBaseHref?: string
): ParsedEmailHtml {
  if (!html.trim()) {
    return { headMarkup: "", bodyHtml: "" }
  }

  if (typeof DOMParser === "undefined") {
    return { headMarkup: "", bodyHtml: html }
  }

  try {
    const doc = new DOMParser().parseFromString(html, "text/html")
    const explicitBase =
      doc.querySelector("base[href]")?.getAttribute("href") ?? undefined
  const documentBaseHref = explicitBase
      ? resolveUrl(explicitBase, undefined)
      : undefined

    doc.querySelector("base[href]")?.remove()

    const headMarkup = collectHeadResourceMarkup(doc, resolveBaseHref)

    let bodyHtml = doc.body?.innerHTML?.trim() ?? ""
    if (!bodyHtml) bodyHtml = html.trim()

    return {
      headMarkup,
      bodyHtml,
      documentBaseHref,
      resolveBaseHref,
    }
  } catch {
    return { headMarkup: "", bodyHtml: html }
  }
}

function rewriteUrlList(value: string, baseHref?: string): string {
  return value
    .split(",")
    .map((part) => {
      const trimmed = part.trim()
      const space = trimmed.indexOf(" ")
      const url = space === -1 ? trimmed : trimmed.slice(0, space)
      const descriptor = space === -1 ? "" : trimmed.slice(space + 1)
      const resolved = resolveUrl(url, baseHref)
      return descriptor ? `${resolved} ${descriptor}` : resolved
    })
    .join(", ")
}

function rewriteStyleRemoteUrls(style: string, baseHref?: string): string {
  return style.replace(
    /url\s*\(\s*['"]?([^'")]+)['"]?\s*\)/gi,
    (_match, url: string) => {
      const trimmed = url.trim()
      if (
        trimmed.startsWith("data:") ||
        trimmed.startsWith("#") ||
        trimmed.startsWith("cid:")
      ) {
        return `url(${trimmed})`
      }
      return `url(${resolveUrl(trimmed, baseHref)})`
    }
  )
}

function rewriteHeadMarkupUrls(headMarkup: string, baseHref?: string): string {
  if (!headMarkup.trim() || !baseHref) return headMarkup
  return headMarkup
    .replace(
      /(<link[^>]+href=)(["'])([^"']+)\2/gi,
      (_m, prefix: string, quote: string, href: string) =>
        `${prefix}${quote}${resolveUrl(href, baseHref)}${quote}`
    )
    .replace(
      /(<style[^>]*>)([\s\S]*?)(<\/style>)/gi,
      (_m, open: string, css: string, close: string) =>
        `${open}${rewriteStyleRemoteUrls(css, baseHref)}${close}`
    )
}

function isRemoteOrRelativeUrl(url: string): boolean {
  const t = url.trim()
  return (
    REMOTE_URL.test(t) ||
    PROTOCOL_RELATIVE.test(t) ||
    (!t.startsWith("data:") &&
      !t.startsWith("cid:") &&
      !t.startsWith("mailto:") &&
      !t.startsWith("#") &&
      !t.startsWith("javascript:"))
  )
}

/** Active images lazy-load et résout les URLs relatives / http. */
export function activateRemoteResourcesInHtml(
  html: string,
  options: { baseHref?: string } = {}
): string {
  const { baseHref } = options
  if (!html.trim() || typeof DOMParser === "undefined") return html

  try {
    const doc = new DOMParser().parseFromString(html, "text/html")

    for (const img of doc.querySelectorAll("img")) {
      const lazySrc = firstLazyImageSrc(img)
      const src = img.getAttribute("src") ?? ""
      const srcIsUseful =
        !!src.trim() &&
        !isPlaceholderImageSrc(src) &&
        (src.startsWith("data:") ||
          src.startsWith("cid:") ||
          isRemoteOrRelativeUrl(src))

      if (lazySrc && isRemoteOrRelativeUrl(lazySrc) && !srcIsUseful) {
        img.setAttribute("src", resolveUrl(lazySrc, baseHref))
      } else if (src.trim() && (src.startsWith("data:") || src.startsWith("cid:"))) {
        /* keep inline / embedded sources */
      } else if (src && isRemoteOrRelativeUrl(src)) {
        img.setAttribute("src", resolveUrl(src, baseHref))
      } else if (lazySrc && isRemoteOrRelativeUrl(lazySrc)) {
        img.setAttribute("src", resolveUrl(lazySrc, baseHref))
      }

      const srcset = img.getAttribute("srcset")
      if (srcset) img.setAttribute("srcset", rewriteUrlList(srcset, baseHref))

      const dataSrcset = img.getAttribute("data-srcset")
      if (dataSrcset && !img.getAttribute("srcset")) {
        img.setAttribute("srcset", rewriteUrlList(dataSrcset, baseHref))
      }

      img.setAttribute("referrerpolicy", "no-referrer")
    }

    for (const el of doc.querySelectorAll("[background]")) {
      const bg = el.getAttribute("background")
      if (!bg || !isRemoteOrRelativeUrl(bg)) continue
      const resolved = resolveUrl(bg, baseHref)
      el.removeAttribute("background")
      const existing = el.getAttribute("style")?.trim() ?? ""
      const bgRule = `background-image:url(${resolved})`
      const nextStyle = existing
        ? existing.endsWith(";")
          ? `${existing}${bgRule}`
          : `${existing};${bgRule}`
        : bgRule
      el.setAttribute("style", nextStyle)
    }

    for (const el of doc.querySelectorAll("[style]")) {
      const style = el.getAttribute("style")
      if (style?.includes("url(")) {
        el.setAttribute("style", rewriteStyleRemoteUrls(style, baseHref))
      }
    }

    for (const source of doc.querySelectorAll("source[src], source[srcset]")) {
      const src = source.getAttribute("src")
      if (src && isRemoteOrRelativeUrl(src)) {
        source.setAttribute("src", resolveUrl(src, baseHref))
      }
      const srcset = source.getAttribute("srcset")
      if (srcset) source.setAttribute("srcset", rewriteUrlList(srcset, baseHref))
    }

    return doc.body.innerHTML
  } catch {
    return html
  }
}

/** Injecte le mail dans le document iframe sans doc.write (préserve les <style>). */
export function injectEmailHtmlIntoDocument(
  doc: Document,
  options: {
    csp: string
    /** Explicit <base href> from the message, if any. */
    documentBaseHref?: string
    /** Inferred origin for relative assets when the message has no <base>. */
    resolveBaseHref?: string
    headMarkup: string
    bodyHtml: string
    wrapperCss: string
  }
): void {
  doc.open()
  doc.write("<!DOCTYPE html><html><head></head><body></body></html>")
  doc.close()

  const head = doc.head
  const body = doc.body
  if (!head || !body) return

  const charset = doc.createElement("meta")
  charset.setAttribute("charset", "utf-8")
  head.appendChild(charset)

  const csp = doc.createElement("meta")
  csp.setAttribute("http-equiv", "Content-Security-Policy")
  csp.setAttribute("content", options.csp)
  head.appendChild(csp)

  const baseHref = options.documentBaseHref ?? options.resolveBaseHref
  if (baseHref) {
    const base = doc.createElement("base")
    base.setAttribute("href", baseHref)
    base.setAttribute("target", "_blank")
    head.appendChild(base)
  }

  const wrapper = doc.createElement("style")
  wrapper.setAttribute("data-ultimail-wrapper", "true")
  wrapper.textContent = options.wrapperCss
  head.appendChild(wrapper)

  if (options.headMarkup.trim()) {
    const tpl = doc.createElement("template")
    tpl.innerHTML = options.headMarkup
    head.append(...Array.from(tpl.content.childNodes))
  }

  body.replaceChildren()
  if (options.bodyHtml.trim()) {
    const tpl = doc.createElement("template")
    tpl.innerHTML = options.bodyHtml
    body.append(...Array.from(tpl.content.childNodes))
  } else {
    const empty = doc.createElement("p")
    empty.textContent = "Ce message n'a pas de contenu affichable."
    empty.setAttribute(
      "style",
      "color:#5f6368;font:14px sans-serif;margin:0;"
    )
    body.appendChild(empty)
  }
}

/** Replace cid: image references with resolved blob or API URLs. */
export function rewriteCidUrlsInHtml(
  html: string,
  cidUrlMap: Record<string, string> | undefined
): string {
  if (!html.trim() || !cidUrlMap || Object.keys(cidUrlMap).length === 0) {
    return html
  }
  if (typeof DOMParser === "undefined") return html

  const resolveCid = (value: string): string => {
    const trimmed = value.trim()
    if (!trimmed.toLowerCase().startsWith("cid:")) return trimmed
    const key = trimmed.slice(4).trim()
    return cidUrlMap[key] ?? cidUrlMap[trimmed] ?? trimmed
  }

  try {
    const doc = new DOMParser().parseFromString(html, "text/html")
    for (const img of doc.querySelectorAll("img")) {
      for (const attr of ["src", "data-src", "data-original", "data-lazy-src"] as const) {
        const value = img.getAttribute(attr)
        if (value?.toLowerCase().startsWith("cid:")) {
          img.setAttribute(attr, resolveCid(value))
        }
      }
      const srcset = img.getAttribute("srcset")
      if (srcset?.includes("cid:")) {
        img.setAttribute(
          "srcset",
          srcset.replace(/cid:[^\s,]+/gi, (match) => resolveCid(match))
        )
      }
    }
    for (const el of doc.querySelectorAll("[style]")) {
      const style = el.getAttribute("style")
      if (style?.includes("cid:")) {
        el.setAttribute(
          "style",
          style.replace(/cid:[^\s'")]+/gi, (match) => resolveCid(match))
        )
      }
    }
    return doc.body.innerHTML
  } catch {
    return html
  }
}

export function prepareEmailHtmlForIframe(
  html: string,
  options: {
    blockRemoteContent: boolean
    isDark: boolean
    senderEmail?: string
    cidUrlMap?: Record<string, string>
  }
): ParsedEmailHtml {
  if (!html.trim()) {
    return { headMarkup: "", bodyHtml: "" }
  }

  const resolveBaseHref =
    inferEmailResolveBaseHref(html) ??
    (options.senderEmail
      ? `https://${options.senderEmail.split("@")[1]?.trim().toLowerCase()}/`
      : undefined)

  if (options.blockRemoteContent) {
    const parsed = parseEmailHtmlForIframe(html, resolveBaseHref)
    const bodyHtml = rewriteCidUrlsInHtml(
      preprocessEmailHtmlForTheme(parsed.bodyHtml || html, options.isDark),
      options.cidUrlMap
    )
    return {
      headMarkup: "",
      bodyHtml,
    }
  }

  const parsed = parseEmailHtmlForIframe(html, resolveBaseHref)
  let bodyHtml = stripHiddenEmailHtml(parsed.bodyHtml)
  bodyHtml = activateRemoteResourcesInHtml(bodyHtml, {
    baseHref: resolveBaseHref,
  })
  bodyHtml = rewriteCidUrlsInHtml(bodyHtml, options.cidUrlMap)

  const headMarkup = rewriteHeadMarkupUrls(parsed.headMarkup, resolveBaseHref)

  return {
    headMarkup,
    bodyHtml,
    documentBaseHref: parsed.documentBaseHref,
    resolveBaseHref,
  }
}