import { MAX_COMMON, MAX_SECTION } from "../constants.ts";
import { normalizeSearch } from "../identity.ts";
import { sortItems } from "../state/usage.ts";
import type { IndexedItem, ResourceIndex } from "../types.ts";

export function escapeMarkdownInline(value: string | undefined): string {
  return (value ?? "").replace(/([\\`*_{}\[\]()#+\-.!|>])/g, "\\$1");
}

function itemTitle(item: IndexedItem): string {
  return escapeMarkdownInline(item.displayName ?? item.name);
}

function formatItem(item: IndexedItem): string {
  const meta = item.sourceLabel ? [escapeMarkdownInline(item.sourceLabel)] : [];
  if (item.scope && item.scope !== "builtin") meta.push(escapeMarkdownInline(item.scope === "project" ? "项目" : item.scope === "user" ? "全局" : item.scope));
  if ((item.useCount ?? 0) > 0) meta.push(`使用 ${item.useCount} 次`);
  if (item.pinned) meta.push("已固定");
  const suffix = meta.length > 0 ? ` · ${meta.join(" · ")}` : "";
  const desc = item.description ? ` — ${escapeMarkdownInline(item.description)}` : "";
  return `- **${itemTitle(item)}**${desc}${suffix}`;
}

function selectTop(items: IndexedItem[], count: number): IndexedItem[] {
  return [...items].sort(sortItems).slice(0, count);
}

function renderSection(title: string, items: IndexedItem[], emptyText: string): string {
  if (items.length === 0) return [`## ${title}`, `- ${emptyText}`].join("\n");
  return [`## ${title}`, items.map(formatItem).join("\n")].join("\n");
}

export function filterIndex(index: ResourceIndex, query?: string): IndexedItem[] {
  const normalizedQuery = normalizeSearch(query);
  return [...index.commands, ...index.tools, ...index.mcp, ...index.packages].filter((item) => {
    if (!normalizedQuery) return true;
    return normalizeSearch([item.name, item.displayName, item.description, item.sourceLabel, item.packageName, item.sourceRef, item.kind].join(" ")).includes(normalizedQuery);
  });
}

export function buildMarkdown(index: ResourceIndex, updatedAt: number | undefined, query?: string): string {
  const normalizedQuery = normalizeSearch(query);
  const allVisible = filterIndex(index, query);

  const commonCommands = selectTop(allVisible.filter((item) => item.kind === "command"), MAX_COMMON);
  const commonTools = selectTop(allVisible.filter((item) => item.kind === "tool"), MAX_COMMON);
  const commonMcp = selectTop(allVisible.filter((item) => item.kind === "mcp"), MAX_COMMON);
  const commonPackages = selectTop(allVisible.filter((item) => item.kind === "package"), MAX_COMMON);

  const commandItems = selectTop(allVisible.filter((item) => item.kind === "command"), MAX_SECTION);
  const toolItems = selectTop(allVisible.filter((item) => item.kind === "tool"), MAX_SECTION);
  const mcpItems = selectTop(allVisible.filter((item) => item.kind === "mcp"), MAX_SECTION);
  const packageItems = selectTop(allVisible.filter((item) => item.kind === "package"), MAX_SECTION);

  const gatewayItems = mcpItems.filter((item) => item.name === "mcp");
  const serverItems = mcpItems.filter((item) => item.name !== "mcp");

  const updated = updatedAt ? new Date(updatedAt).toLocaleString() : new Date().toLocaleString();
  const title = normalizedQuery ? `动态帮助 · 搜索：${escapeMarkdownInline(query?.trim())}` : "动态帮助";

  return [
    `# ${title}`,
    `_更新时间：${updated}_`,
    "",
    `> 已加载：${index.commands.length} 条命令 · ${index.tools.length} 个工具 · ${index.mcp.length} 个 MCP 服务器 · ${index.packages.length} 个包`,
    "",
    renderSection("常用命令", commonCommands, "暂无"),
    "",
    renderSection("常用工具", commonTools, "暂无"),
    "",
    renderSection("常用 MCP 服务器", commonMcp, "暂无"),
    "",
    renderSection("常用包", commonPackages, "暂无"),
    "",
    "## 命令",
    commandItems.length > 0 ? commandItems.map(formatItem).join("\n") : "- 暂无",
    "",
    "## 工具",
    toolItems.length > 0 ? toolItems.map(formatItem).join("\n") : "- 暂无",
    "",
    "## MCP 服务器",
    "### 网关",
    gatewayItems.length > 0 ? gatewayItems.map(formatItem).join("\n") : "- 暂无",
    "",
    "### 服务器",
    serverItems.length > 0 ? serverItems.map(formatItem).join("\n") : "- 暂无",
    "",
    "## 包",
    packageItems.length > 0 ? packageItems.map(formatItem).join("\n") : "- 暂无",
    "",
    "## 操作",
    "- `/help search <词>` 搜索当前索引",
    "- `/help pin <词>` 固定匹配项",
    "- `/help unpin <词>` 取消固定",
    "- `/help refresh` 重新扫描并刷新使用统计",
  ].join("\n");
}