"use client";

// @contract-pending：studentLessonPlanView schema 未实现，全 MSW 兜底
// @contract-pending scope-check：范围校验待 core-edu 服务接入后启用
/**
 * 学生教案只读查看页 - 客户端组件（ARCHITECTURE.md §7.3 详情页 / §9.1 / §10 P2）
 *
 * 数据契约：
 * - studentLessonPlanView(planId) ❌ schema 无此字段 → MSW 兜底（@contract-pending）
 * - 契约工单：docs/architecture/issues/contracts/core-edu_contract.md
 *
 * 三态规范（§11.3 DoD）：
 * - loading：DetailPageSkeleton
 * - error：errorNode 局部降级
 * - notFound：data 为 null 时显示空态节点
 *
 * 范围校验（@contract-pending scope-check）：
 * - 当前 portal-shell 使用 MSW 兜底，无真实 ctx.dataScope
 * - TODO: 待 core-edu 服务接入后，调用 assertPlanInScope(plan, ctx) 校验范围
 *
 * 关联：ARCHITECTURE.md §5.3 / §5.4 / §7.3 / §9.1 / §10 P2 / §11.3 / §11.4
 */
import { FileText } from "lucide-react";
import { useParams } from "next/navigation";
import { useTranslations } from "next-intl";
import { useEffect, useMemo, type ReactNode } from "react";

import {
  useStudentLessonPlanView,
  type StudentLessonPlanView as LessonPlanViewData,
} from "@/lib/api";
import { EmptyState } from "@/shared/components/ui/empty-state";
import {
  DetailPageShell,
  DetailPageSkeleton,
  DetailSection,
  DetailField,
} from "@/shared/components/page-templates";
import { notify } from "@/shared/lib/notify";

/**
 * 只读查看客户端主体。需由 server page 包裹在 <Suspense> 中。
 *
 * 全高度布局（h-[calc(100vh-4rem)]）+ 内部 overflow-y-auto，提升阅读体验。
 */
export function StudentLessonPlanViewClient(): React.ReactElement {
  const t = useTranslations("studentDomain.lessonPlans.view");
  const tCommon = useTranslations("common");
  const params = useParams<{ planId: string }>();
  const planId = params?.planId ?? "";

  // @contract-pending：MSW 兜底
  const { data, loading, error } = useStudentLessonPlanView(planId);

  useEffect(() => {
    if (error) {
      notify.error(tCommon("error.loadFailed", { message: String(error) }));
    }
  }, [error, tCommon]);

  const errorNode = error ? (
    <div className="rounded-xl border border-destructive/30 bg-destructive/5 p-6 text-center">
      <p className="text-sm text-destructive">
        {tCommon("error.loadFailed", { message: String(error) })}
      </p>
    </div>
  ) : undefined;

  const emptyNode =
    !loading && !error && !data ? (
      <EmptyState
        icon={FileText}
        title={t("notFound")}
        action={{
          label: t("backToList"),
          href: "/shell/student/lesson-plans",
        }}
      />
    ) : undefined;

  return (
    <div className="h-[calc(100vh-4rem)] overflow-y-auto">
      <DetailPageShell
        title={data?.title ?? t("title")}
        description={data ? buildSubtitle(data, t) : undefined}
        icon={<FileText className="size-6" />}
        backHref="/shell/student/lesson-plans"
        loading={loading}
        loadingNode={<DetailPageSkeleton />}
        errorNode={errorNode}
        emptyNode={emptyNode}
      >
        {data ? <LessonPlanViewBody plan={data} /> : null}
      </DetailPageShell>
    </div>
  );
}

/**
 * 构造副标题字符串：优先教材/章节，缺失时退化为学科/年级。
 */
function buildSubtitle(
  plan: LessonPlanViewData,
  t: ReturnType<typeof useTranslations>,
): string {
  const parts: string[] = [];
  if (plan.textbookTitle) {
    parts.push(`${t("fieldTextbook")}: ${plan.textbookTitle}`);
  }
  if (plan.chapterTitle) {
    parts.push(`${t("fieldChapter")}: ${plan.chapterTitle}`);
  }
  if (parts.length === 0) {
    parts.push(`${t("fieldSubject")}: ${plan.subject}`);
    parts.push(`${t("fieldGrade")}: ${plan.grade}`);
  }
  return parts.join(" · ");
}

/**
 * 教案查看主体（基本信息 + 教案内容）。
 *
 * 已发布状态检查：status !== "published" 时显示友好提示并阻止渲染内容。
 * 范围校验占位：@contract-pending scope-check（见文件头 TODO）
 */
function LessonPlanViewBody({
  plan,
}: {
  plan: LessonPlanViewData;
}): React.ReactElement {
  const t = useTranslations("studentDomain.lessonPlans.view");

  // TODO: 待 core-edu 服务接入后，调用 assertPlanInScope(plan, ctx) 校验范围
  // @contract-pending scope-check

  // 已发布状态检查：未发布时阻止渲染内容
  if (plan.status && plan.status !== "published") {
    return (
      <div className="rounded-xl border border-border bg-muted/50 p-6 text-center">
        <p className="text-sm text-muted-foreground">{t("notPublished")}</p>
      </div>
    );
  }

  return (
    <div className="flex flex-col gap-6">
      <DetailSection title={t("sectionBasic")}>
        <DetailField label={t("fieldSubject")} value={plan.subject} />
        <DetailField label={t("fieldGrade")} value={plan.grade} />
        {plan.textbookTitle ? (
          <DetailField label={t("fieldTextbook")} value={plan.textbookTitle} />
        ) : null}
        {plan.chapterTitle ? (
          <DetailField label={t("fieldChapter")} value={plan.chapterTitle} />
        ) : null}
      </DetailSection>

      <DetailSection title={t("sectionContent")}>
        <RichLessonContent content={plan.content} />
      </DetailSection>
    </div>
  );
}

/* ------------------------------------------------------------------ *
 * 富文档渲染（自研简易解析，不引入新依赖）
 *
 * 支持两种内容形式：
 * 1. 结构化 JSON：{ sections: [{ title, content, items }] }
 * 2. 简易 markdown 文本：标题（#/##/###、中文序号"一、二、…"）、
 *    有序列表（1.）、无序列表（-/*）、段落、行内加粗（**text**）
 * ------------------------------------------------------------------ */

/** 块级节点类型 */
type BlockNode =
  | {
      readonly type: "heading";
      readonly level: 1 | 2 | 3;
      readonly text: string;
    }
  | { readonly type: "paragraph"; readonly text: string }
  | {
      readonly type: "list";
      readonly ordered: boolean;
      readonly items: readonly string[];
    };

/** 中文序号正则：一、二、三、... 十、十一、… */
const CN_HEADING_RE = /^[一二三四五六七八九十]+、\s*(.+)$/;
/** 阿拉伯数字有序列表项：1. xxx */
const OL_RE = /^\d+\.\s+(.+)$/;
/** 无序列表项：- xxx 或 * xxx */
const UL_RE = /^[-*]\s+(.+)$/;
/** Markdown 标题：# xxx / ## xxx / ### xxx */
const MD_HEADING_RE = /^(#{1,3})\s+(.+)$/;
/** 行内加粗：**text** */
const BOLD_RE = /\*\*([^*]+)\*\*/;

/** 类型守卫：判断 value 是否为字符串 */
function isString(value: unknown): value is string {
  return typeof value === "string";
}

/** 类型守卫：判断 value 是否为结构化 sections 文档 */
function isStructuredDoc(value: unknown): value is {
  sections: ReadonlyArray<{
    title?: unknown;
    content?: unknown;
    items?: unknown;
  }>;
} {
  if (typeof value !== "object" || value === null) return false;
  if (!("sections" in value)) return false;
  // 从 unknown 转换为具体类型（允许的 as 场景）
  const obj = value as { sections: unknown };
  return Array.isArray(obj.sections);
}

/** 将数字钳制到 1-3 区间（用于标题层级） */
function clampLevel(n: number): 1 | 2 | 3 {
  if (n >= 3) return 3;
  if (n === 2) return 2;
  return 1;
}

/**
 * 解析教案内容字符串为块级节点数组。
 *
 * 优先尝试 JSON 结构化解析；失败则按简易 markdown 文本解析。
 */
function parseLessonContent(content: string): readonly BlockNode[] {
  if (content.trim().startsWith("{")) {
    try {
      const parsed: unknown = JSON.parse(content);
      if (isStructuredDoc(parsed)) {
        return parseStructuredSections(parsed.sections);
      }
    } catch {
      // JSON 解析失败，回退到文本解析
    }
  }
  return parseMarkdownLike(content);
}

/** 解析结构化 sections 为块级节点 */
function parseStructuredSections(
  sections: ReadonlyArray<{
    title?: unknown;
    content?: unknown;
    items?: unknown;
  }>,
): readonly BlockNode[] {
  const nodes: BlockNode[] = [];
  for (const section of sections) {
    if (isString(section.title) && section.title.length > 0) {
      nodes.push({ type: "heading", level: 2, text: section.title });
    }
    if (isString(section.content) && section.content.length > 0) {
      nodes.push({ type: "paragraph", text: section.content });
    }
    if (Array.isArray(section.items)) {
      const items = section.items.filter(isString);
      if (items.length > 0) {
        nodes.push({ type: "list", ordered: false, items });
      }
    }
  }
  return nodes;
}

/** 解析简易 markdown 文本为块级节点 */
function parseMarkdownLike(content: string): readonly BlockNode[] {
  const lines = content.split(/\r?\n/);
  const nodes: BlockNode[] = [];
  let i = 0;
  while (i < lines.length) {
    const line = lines[i] ?? "";
    const trimmed = line.trim();

    // 空行：跳过（段落分隔由节点边界自然形成）
    if (trimmed === "") {
      i += 1;
      continue;
    }

    // Markdown 标题
    const mdMatch = MD_HEADING_RE.exec(trimmed);
    if (mdMatch) {
      const hashes = mdMatch[1] ?? "";
      const text = mdMatch[2] ?? "";
      nodes.push({ type: "heading", level: clampLevel(hashes.length), text });
      i += 1;
      continue;
    }

    // 中文序号标题（一、二、三、）
    const cnMatch = CN_HEADING_RE.exec(trimmed);
    if (cnMatch) {
      const text = cnMatch[1] ?? "";
      nodes.push({ type: "heading", level: 2, text });
      i += 1;
      continue;
    }

    // 有序列表
    if (OL_RE.test(trimmed)) {
      const items: string[] = [];
      while (i < lines.length) {
        const cur = (lines[i] ?? "").trim();
        const m = OL_RE.exec(cur);
        if (!m) break;
        items.push(m[1] ?? "");
        i += 1;
      }
      nodes.push({ type: "list", ordered: true, items });
      continue;
    }

    // 无序列表
    if (UL_RE.test(trimmed)) {
      const items: string[] = [];
      while (i < lines.length) {
        const cur = (lines[i] ?? "").trim();
        const m = UL_RE.exec(cur);
        if (!m) break;
        items.push(m[1] ?? "");
        i += 1;
      }
      nodes.push({ type: "list", ordered: false, items });
      continue;
    }

    // 段落
    nodes.push({ type: "paragraph", text: trimmed });
    i += 1;
  }
  return nodes;
}

/** 渲染行内文本（处理 **bold** 加粗） */
function renderInline(text: string): ReactNode[] {
  const parts: ReactNode[] = [];
  let remaining = text;
  let key = 0;
  while (remaining.length > 0) {
    const m = BOLD_RE.exec(remaining);
    if (!m) {
      parts.push(remaining);
      break;
    }
    if (m.index > 0) {
      parts.push(remaining.slice(0, m.index));
    }
    parts.push(
      <strong key={`b-${key}`} className="font-semibold">
        {m[1]}
      </strong>,
    );
    key += 1;
    remaining = remaining.slice(m.index + m[0].length);
  }
  return parts;
}

/**
 * 富文档渲染组件。
 *
 * 将教案内容字符串解析为块级节点并渲染：标题（h2/h3/h4）、段落（p）、
 * 有序/无序列表（ol/ul + li）。纯文本场景保留 whitespace-pre-wrap。
 */
function RichLessonContent({
  content,
}: {
  content: string;
}): React.ReactElement {
  const nodes = useMemo(() => parseLessonContent(content), [content]);

  // 纯文本退化：仅单个段落且无结构时，保留 whitespace-pre-wrap
  if (nodes.length === 1 && nodes[0]?.type === "paragraph") {
    return (
      <div className="whitespace-pre-wrap rounded-md border bg-card p-4 text-sm leading-7 text-foreground">
        {renderInline(nodes[0].text)}
      </div>
    );
  }

  return (
    <div className="space-y-3 rounded-md border bg-card p-4">
      {nodes.map((node, idx) => {
        const key = `block-${idx}`;
        if (node.type === "heading") {
          if (node.level === 1) {
            return (
              <h2
                key={key}
                className="mt-4 text-xl font-bold text-foreground first:mt-0"
              >
                {renderInline(node.text)}
              </h2>
            );
          }
          if (node.level === 2) {
            return (
              <h3
                key={key}
                className="mt-3 text-lg font-semibold text-foreground first:mt-0"
              >
                {renderInline(node.text)}
              </h3>
            );
          }
          return (
            <h4
              key={key}
              className="mt-2 text-base font-semibold text-foreground first:mt-0"
            >
              {renderInline(node.text)}
            </h4>
          );
        }
        if (node.type === "paragraph") {
          return (
            <p
              key={key}
              className="whitespace-pre-wrap leading-7 text-foreground"
            >
              {renderInline(node.text)}
            </p>
          );
        }
        // list
        if (node.ordered) {
          return (
            <ol key={key} className="ml-5 list-decimal space-y-1">
              {node.items.map((item, i) => (
                <li key={`li-${i}`} className="leading-7 text-foreground">
                  {renderInline(item)}
                </li>
              ))}
            </ol>
          );
        }
        return (
          <ul key={key} className="ml-5 list-disc space-y-1">
            {node.items.map((item, i) => (
              <li key={`li-${i}`} className="leading-7 text-foreground">
                {renderInline(item)}
              </li>
            ))}
          </ul>
        );
      })}
    </div>
  );
}