<script setup lang="ts">
import { ref, watch, nextTick } from "vue";
import { unified } from "unified";
import remarkParse from "remark-parse";
import remarkGfm from "remark-gfm";
import remarkRehype from "remark-rehype";
import rehypeStringify from "rehype-stringify";
import rehypeSanitize from "rehype-sanitize";

const props = withDefaults(
  defineProps<{
    modelValue?: string;
    placeholder?: string;
    previewOnly?: boolean;
  }>(),
  {
    modelValue: "",
    placeholder: "开始写作...",
    previewOnly: false,
  },
);

const emit = defineEmits<{
  "update:modelValue": [value: string];
  "save-shortcut": [];
}>();

// ── Unified processors ─────────────────────────────────────────────

/** Full pipeline: markdown → HTML */
const md2html = unified()
  .use(remarkParse)
  .use(remarkGfm)
  .use(remarkRehype, { allowDangerousHtml: false })
  .use(rehypeSanitize)
  .use(rehypeStringify);

// ── Rendering ──────────────────────────────────────────────────────

const renderedHtml = ref("");
const renderError = ref(false);

function renderFullHtml(md: string) {
  try {
    const file = md2html.processSync(md);
    renderedHtml.value = String(file.value);
    renderError.value = false;
  } catch {
    renderedHtml.value = "";
    renderError.value = true;
  }
}

watch(
  () => props.modelValue,
  (val) => {
    renderFullHtml(val);
    // 切换文件时重置滚动位置到顶部
    nextTick(() => {
      if (scrollRef.value) scrollRef.value.scrollTop = 0;
    });
  },
  { immediate: true },
);

// ── Editor textarea handlers ───────────────────────────────────────

const editorTextareaRef = ref<HTMLTextAreaElement>();
const scrollRef = ref<HTMLDivElement>();

function onEditorInput(e: Event) {
  const val = (e.target as HTMLTextAreaElement).value;
  emit("update:modelValue", val);
  renderFullHtml(val);
}

function tryAutoPair(
  ta: HTMLTextAreaElement,
  key: string,
): boolean {
  const pairs: Record<string, string> = {
    "(": ")",
    "[": "]",
    "{": "}",
    '"': '"',
    "'": "'",
    "`": "`",
  };
  const close = pairs[key];
  if (!close) return false;

  const start = ta.selectionStart;
  const end = ta.selectionEnd;
  const selected = props.modelValue.substring(start, end);
  const newVal =
    props.modelValue.substring(0, start) +
    key +
    selected +
    close +
    props.modelValue.substring(end);

  emit("update:modelValue", newVal);
  renderFullHtml(newVal);

  void nextTick(() => {
    ta.selectionStart = start + 1;
    ta.selectionEnd = start + 1 + selected.length;
    ta.focus();
  });
  return true;
}

function onEditorKeydown(e: KeyboardEvent) {
  if ((e.ctrlKey || e.metaKey) && e.key === "s") {
    e.preventDefault();
    emit("save-shortcut");
    return;
  }

  const ta = e.target as HTMLTextAreaElement;

  if (e.key === "Tab") {
    e.preventDefault();
    const start = ta.selectionStart;
    const end = ta.selectionEnd;
    const newVal =
      props.modelValue.substring(0, start) +
      "  " +
      props.modelValue.substring(end);
    emit("update:modelValue", newVal);
    renderFullHtml(newVal);
    void nextTick(() => {
      ta.selectionStart = ta.selectionEnd = start + 2;
      ta.focus();
    });
    return;
  }

  if (tryAutoPair(ta, e.key)) {
    e.preventDefault();
    return;
  }
}
</script>

<template>
  <div
    ref="scrollRef"
    class="flex-1 w-full overflow-auto"
    @wheel.passive
  >
    <div
      class="mx-auto px-8 pb-40 pt-8 h-full"
      :style="{
        maxWidth: `calc(700px * var(--editor-zoom, 1))`,
        fontSize: `calc(1rem * var(--editor-zoom, 1))`,
      }"
    >
      <!-- Editor mode -->
      <textarea
        v-if="!previewOnly"
        ref="editorTextareaRef"
        :value="props.modelValue"
        :placeholder="props.placeholder"
        class="
          w-full h-full min-h-[60vh] resize-none bg-transparent outline-none
          font-serif text-[#38342e] leading-relaxed
          placeholder:text-[#b8b3a8]
        "
        @input="onEditorInput"
        @keydown="onEditorKeydown"
      />

      <!-- Preview mode -->
      <div v-else class="min-h-[60vh]">
        <div v-if="renderError" class="text-red-500 text-sm">
          ⚠ Markdown 解析错误
        </div>
        <div v-else class="markdown-preview" v-html="renderedHtml" />
      </div>
    </div>
  </div>
</template>

<style>
/* ── Markdown Preview Styles (warm palette) ─────────────────────── */

.markdown-preview {
  font-family: ui-serif, Georgia, Cambria, "Times New Roman", Times, serif;
  line-height: 1.625;
  color: #38342e;
  word-break: break-word;
}

.markdown-preview > *:first-child { margin-top: 0; }

.markdown-preview h1,
.markdown-preview h2,
.markdown-preview h3,
.markdown-preview h4,
.markdown-preview h5,
.markdown-preview h6 {
  font-weight: 700;
  color: #2d2a26;
  line-height: 1.3;
  margin-top: 1.5em;
  margin-bottom: 0.5em;
}
.markdown-preview h1 { font-size: 1.5em; }
.markdown-preview h2 { font-size: 1.25em; }
.markdown-preview h3 { font-size: 1.125em; }
.markdown-preview h4 { font-size: 1em; }

.markdown-preview p { margin: 0.5em 0; }

.markdown-preview strong { font-weight: 700; color: #2d2a26; }
.markdown-preview em { font-style: italic; }
.markdown-preview del { text-decoration: line-through; color: #8c877d; }

.markdown-preview code {
  background-color: #f4f1ea;
  color: #bf6a3b;
  border-radius: 0.25rem;
  padding: 0.125rem 0.375rem;
  font-size: 0.875em;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;
  word-break: break-all;
}

.markdown-preview pre {
  background-color: #f4f1ea;
  border-radius: 0.375rem;
  padding: 1rem;
  overflow-x: auto;
  margin: 0.75em 0;
}
.markdown-preview pre code {
  background: none;
  padding: 0;
  color: #38342e;
  font-size: 0.875em;
  border-radius: 0;
  word-break: normal;
}

.markdown-preview a { color: #bf6a3b; text-decoration: underline; }

.markdown-preview blockquote {
  border-left: 4px solid #bf6a3b;
  padding-left: 1rem;
  margin: 0.75em 0;
  color: #8c877d;
  font-style: italic;
}
.markdown-preview blockquote p { margin: 0.25em 0; }

.markdown-preview ul { list-style-type: disc; padding-left: 1.5em; margin: 0.5em 0; }
.markdown-preview ol { list-style-type: decimal; padding-left: 1.5em; margin: 0.5em 0; }
.markdown-preview li { margin: 0.25em 0; }

.markdown-preview li input[type="checkbox"] {
  margin-right: 0.375rem;
  accent-color: #bf6a3b;
}

.markdown-preview hr {
  border: none;
  border-top: 1px solid #e0dbcf;
  margin: 1.5em 0;
}

.markdown-preview table {
  border-collapse: collapse;
  width: 100%;
  margin: 0.75em 0;
}
.markdown-preview th,
.markdown-preview td {
  border: 1px solid #e0dbcf;
  padding: 0.5rem 0.75rem;
  text-align: left;
}
.markdown-preview th {
  background-color: #f4f1ea;
  font-weight: 700;
  color: #2d2a26;
}
.markdown-preview tr:nth-child(even) td { background-color: #faf9f6; }

.markdown-preview img {
  max-width: 100%;
  height: auto;
  border-radius: 0.25rem;
  margin: 0.5em 0;
}
</style>
