384 lines
11 KiB
C++
384 lines
11 KiB
C++
#include "app.hpp"
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#include <fstream>
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#include <sstream>
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#include <algorithm>
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#include <cctype>
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#include <cstdio>
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#include <stdexcept>
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// ============================================================
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// 匿名命名空间：简易 JSON 序列化 / 反序列化
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// 仅支持当前 TodoItem 数据结构的 JSON 子集，无外部依赖。
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// ============================================================
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namespace {
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/**
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* @brief 将字符串中的特殊字符转义为 JSON 安全形式。
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*/
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static std::string json_escape(const std::string& s) {
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std::string r;
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r.reserve(s.size() + 4);
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for (char c : s) {
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switch (c) {
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case '"': r += "\\\""; break;
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case '\\': r += "\\\\"; break;
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case '\n': r += "\\n"; break;
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case '\t': r += "\\t"; break;
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case '\r': r += "\\r"; break;
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default: r += c; break;
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}
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}
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return r;
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}
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/**
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* @brief 将 TodoItem 列表和 next_id 序列化为 JSON 字符串。
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*/
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static std::string items_to_json(const std::vector<TodoItem>& items, int next_id) {
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std::ostringstream oss;
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oss << "{\n \"items\": [\n";
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for (size_t i = 0; i < items.size(); ++i) {
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const auto& it = items[i];
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oss << " {\n";
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oss << " \"id\": " << it.id << ",\n";
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oss << " \"title\": \"" << json_escape(it.title) << "\",\n";
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oss << " \"description\": \"" << json_escape(it.description) << "\",\n";
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oss << " \"completed\": " << (it.completed ? "true" : "false") << "\n";
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oss << " }";
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if (i + 1 < items.size()) oss << ",";
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oss << "\n";
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}
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oss << " ],\n \"next_id\": " << next_id << "\n}\n";
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return oss.str();
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}
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/**
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* @brief 简易递归下降 JSON 解析器，专用于解析 TodoItem 数据格式。
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*
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* 支持 JSON 子集：对象、数组、字符串、整数、布尔值。
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* 不依赖任何外部库。
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*/
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class JsonReader {
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public:
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explicit JsonReader(const std::string& input)
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: s_(input), pos_(0) {}
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/**
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* @brief 解析顶层 JSON 对象，提取 items 和 next_id。
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* @param[out] items 解析出的任务列表
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* @param[out] next_id 解析出的下一个可用 ID
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* @return 解析成功返回 true
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*/
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bool parse(std::vector<TodoItem>& items, int& next_id) {
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items.clear();
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skip_ws();
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if (peek() != '{') return false;
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advance(); // 跳过 '{'
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while (pos_ < s_.size() && peek() != '}') {
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skip_ws();
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if (peek() == '}') break;
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if (peek() == ',') { advance(); continue; }
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std::string key = parse_string();
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skip_ws();
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if (peek() != ':') return false;
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advance();
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skip_ws();
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if (key == "items") {
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if (!parse_array(items)) return false;
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} else if (key == "next_id") {
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next_id = parse_int();
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} else {
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skip_value();
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}
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}
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if (peek() == '}') advance();
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return true;
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}
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private:
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const std::string& s_;
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size_t pos_ = 0;
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/// @brief 查看当前字符，不移动指针。
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char peek() const { return pos_ < s_.size() ? s_[pos_] : '\0'; }
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/// @brief 读取当前字符并前进一位。
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char advance() { return pos_ < s_.size() ? s_[pos_++] : '\0'; }
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/// @brief 跳过空白字符。
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void skip_ws() {
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while (pos_ < s_.size() &&
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std::isspace(static_cast<unsigned char>(s_[pos_]))) {
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++pos_;
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}
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}
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/// @brief 解析 JSON 字符串（含引号和转义处理）。
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std::string parse_string() {
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skip_ws();
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if (peek() != '"') return {};
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advance(); // 跳过开头的 "
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std::string result;
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while (pos_ < s_.size() && s_[pos_] != '"') {
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if (s_[pos_] == '\\') {
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advance();
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if (pos_ < s_.size()) {
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switch (s_[pos_]) {
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case '"': result += '"'; break;
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case '\\': result += '\\'; break;
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case '/': result += '/'; break;
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case 'n': result += '\n'; break;
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case 't': result += '\t'; break;
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case 'r': result += '\r'; break;
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default: result += s_[pos_]; break;
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}
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}
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} else {
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result += s_[pos_];
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}
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++pos_;
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}
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if (peek() == '"') advance(); // 跳过结尾的 "
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return result;
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}
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/// @brief 解析整数值（可选负号）。
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int parse_int() {
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skip_ws();
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int sign = 1;
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if (peek() == '-') { sign = -1; advance(); }
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int val = 0;
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while (pos_ < s_.size() &&
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std::isdigit(static_cast<unsigned char>(s_[pos_]))) {
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val = val * 10 + (s_[pos_] - '0');
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++pos_;
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}
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return sign * val;
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}
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/**
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* @brief 解析布尔值 true / false。
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* @param[out] value 解析结果
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* @return 解析成功返回 true
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*/
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bool parse_bool(bool& value) {
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skip_ws();
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if (s_.substr(pos_, 4) == "true") {
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pos_ += 4;
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value = true;
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return true;
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}
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if (s_.substr(pos_, 5) == "false") {
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pos_ += 5;
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value = false;
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return true;
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}
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return false;
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}
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/**
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* @brief 解析 JSON 数组，元素为 TodoItem 对象。
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*/
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bool parse_array(std::vector<TodoItem>& items) {
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skip_ws();
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if (peek() != '[') return false;
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advance(); // 跳过 '['
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while (pos_ < s_.size() && peek() != ']') {
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skip_ws();
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if (peek() == ']') break;
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if (peek() == ',') { advance(); continue; }
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TodoItem item;
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if (!parse_object(item)) return false;
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items.push_back(std::move(item));
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}
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if (peek() == ']') advance();
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return true;
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}
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/**
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* @brief 解析单个 TodoItem JSON 对象。
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*/
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bool parse_object(TodoItem& item) {
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skip_ws();
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if (peek() != '{') return false;
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advance(); // 跳过 '{'
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while (pos_ < s_.size() && peek() != '}') {
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skip_ws();
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if (peek() == '}') break;
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if (peek() == ',') { advance(); continue; }
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std::string key = parse_string();
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skip_ws();
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if (peek() != ':') return false;
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advance();
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skip_ws();
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if (key == "id") {
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item.id = parse_int();
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} else if (key == "title") {
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item.title = parse_string();
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} else if (key == "description") {
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item.description = parse_string();
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} else if (key == "completed") {
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bool val = false;
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if (parse_bool(val)) item.completed = val;
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} else {
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skip_value();
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}
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}
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if (peek() == '}') advance();
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return true;
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}
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/// @brief 跳过任意 JSON 值（用于忽略不关心的字段）。
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void skip_value() {
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skip_ws();
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char c = peek();
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if (c == '"') {
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parse_string();
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} else if (c == '{') {
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int depth = 1;
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advance();
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while (pos_ < s_.size() && depth > 0) {
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if (s_[pos_] == '{') ++depth;
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else if (s_[pos_] == '}') --depth;
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else if (s_[pos_] == '"') {
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++pos_;
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while (pos_ < s_.size() && s_[pos_] != '"') {
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if (s_[pos_] == '\\') ++pos_;
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++pos_;
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}
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}
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++pos_;
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}
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} else if (c == '[') {
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int depth = 1;
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advance();
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while (pos_ < s_.size() && depth > 0) {
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if (s_[pos_] == '[') ++depth;
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else if (s_[pos_] == ']') --depth;
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else if (s_[pos_] == '"') {
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++pos_;
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while (pos_ < s_.size() && s_[pos_] != '"') {
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if (s_[pos_] == '\\') ++pos_;
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++pos_;
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}
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}
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++pos_;
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}
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} else {
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// 数字、布尔值、null 等
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while (pos_ < s_.size() &&
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!std::isspace(static_cast<unsigned char>(s_[pos_])) &&
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s_[pos_] != ',' && s_[pos_] != '}' && s_[pos_] != ']') {
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++pos_;
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}
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}
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}
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};
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} // anonymous namespace
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// ============================================================
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// TodoService 实现
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// ============================================================
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TodoService::TodoService(const std::string& filepath)
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: filepath_(filepath) {
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load();
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}
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const std::vector<TodoItem>& TodoService::get_all() const {
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return items_;
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}
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std::optional<TodoItem> TodoService::get_by_id(int id) const {
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for (const auto& item : items_) {
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if (item.id == id) return item;
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}
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return std::nullopt;
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}
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TodoItem TodoService::create(const std::string& title,
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const std::string& description) {
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TodoItem item;
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item.id = next_id_++;
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item.title = title;
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item.description = description;
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item.completed = false;
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items_.push_back(item);
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save();
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return item;
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}
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std::optional<TodoItem> TodoService::update(
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int id,
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const std::optional<std::string>& title,
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const std::optional<std::string>& description,
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const std::optional<bool>& completed) {
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for (auto& item : items_) {
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if (item.id == id) {
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if (title.has_value()) item.title = title.value();
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if (description.has_value()) item.description = description.value();
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if (completed.has_value()) item.completed = completed.value();
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save();
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return item;
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}
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}
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return std::nullopt;
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}
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bool TodoService::delete_item(int id) {
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auto it = std::find_if(items_.begin(), items_.end(),
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[id](const TodoItem& item) { return item.id == id; });
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if (it == items_.end()) return false;
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items_.erase(it);
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save();
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return true;
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}
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void TodoService::load() {
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std::ifstream ifs(filepath_);
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if (!ifs.is_open()) {
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items_.clear();
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next_id_ = 1;
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return;
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}
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std::stringstream buffer;
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buffer << ifs.rdbuf();
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std::string content = buffer.str();
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if (content.empty()) {
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items_.clear();
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next_id_ = 1;
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return;
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}
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items_.clear();
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int parsed_next_id = 1;
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JsonReader reader(content);
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if (reader.parse(items_, parsed_next_id)) {
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next_id_ = parsed_next_id;
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// 确保 next_id 大于所有现有 ID，避免冲突
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for (const auto& item : items_) {
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if (item.id >= next_id_) next_id_ = item.id + 1;
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}
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} else {
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// 解析失败时回退到空状态
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items_.clear();
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next_id_ = 1;
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}
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}
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void TodoService::save() {
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std::ofstream ofs(filepath_);
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if (!ofs.is_open()) return;
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ofs << items_to_json(items_, next_id_);
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}
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