/* Copyright (c) 2013 Dropbox, Inc.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "json11.hpp"
#include <cassert>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <limits>
#include <locale>
#include <sstream>

namespace json11
{

static const int max_depth = 200;

using std::initializer_list;
using std::make_shared;
using std::map;
using std::move;
using std::string;
using std::vector;

/* Helper for representing null - just a do-nothing struct, plus comparison
 * operators so the helpers in JsonValue work. We can't use nullptr_t because
 * it may not be orderable.
 */
struct NullStruct
{
    bool operator==(NullStruct) const { return true; }
    bool operator<(NullStruct) const { return false; }
};

/* * * * * * * * * * * * * * * * * * * *
 * Serialization
 */

static void dump(NullStruct, string& out)
{
    out += "null";
}

static void dump(double value, string& out)
{
    if (std::isfinite(value))
    {
        std::ostringstream stm;
        stm.imbue(std::locale("C"));
        stm << value;
        out += stm.str();
    }
    else
    {
        out += "null";
    }
}

static void dump(int value, string& out)
{
    char buf[32];
    snprintf(buf, sizeof buf, "%d", value);
    out += buf;
}

static void dump(bool value, string& out)
{
    out += value ? "true" : "false";
}

static void dump(const string& value, string& out)
{
    out += '"';
    for (std::size_t i = 0; i < value.length(); i++)
    {
        const char ch = value[i];
        if (ch == '\\')
        {
            out += "\\\\";
        }
        else if (ch == '"')
        {
            out += "\\\"";
        }
        else if (ch == '\b')
        {
            out += "\\b";
        }
        else if (ch == '\f')
        {
            out += "\\f";
        }
        else if (ch == '\n')
        {
            out += "\\n";
        }
        else if (ch == '\r')
        {
            out += "\\r";
        }
        else if (ch == '\t')
        {
            out += "\\t";
        }
        else if (static_cast<std::uint8_t>(ch) <= 0x1f)
        {
            char buf[8];
            snprintf(buf, sizeof buf, "\\u%04x", ch);
            out += buf;
        }
        else if (static_cast<std::uint8_t>(ch) == 0xe2 && static_cast<std::uint8_t>(value[i + 1]) == 0x80
            && static_cast<std::uint8_t>(value[i + 2]) == 0xa8)
        {
            out += "\\u2028";
            i += 2;
        }
        else if (static_cast<std::uint8_t>(ch) == 0xe2 && static_cast<std::uint8_t>(value[i + 1]) == 0x80
            && static_cast<std::uint8_t>(value[i + 2]) == 0xa9)
        {
            out += "\\u2029";
            i += 2;
        }
        else
        {
            out += ch;
        }
    }
    out += '"';
}

static void dump(const Json::array& values, string& out)
{
    bool first = true;
    out += "[";
    for (const auto& value : values)
    {
        if (!first)
            out += ", ";
        value.dump(out);
        first = false;
    }
    out += "]";
}

static void dump(const Json::object& values, string& out)
{
    bool first = true;
    out += "{";
    for (const auto& kv : values)
    {
        if (!first)
            out += ", ";
        dump(kv.first, out);
        out += ": ";
        kv.second.dump(out);
        first = false;
    }
    out += "}";
}

void Json::dump(string& out) const
{
    m_ptr->dump(out);
}

/* * * * * * * * * * * * * * * * * * * *
 * Value wrappers
 */

template <Json::Type tag, typename T>
class Value : public JsonValue
{
protected:
    // Constructors
    explicit Value(const T& value)
        : m_value(value)
    {
    }
    explicit Value(T&& value)
        : m_value(move(value))
    {
    }

    // Get type tag
    Json::Type type() const override
    {
        return tag;
    }

    // Comparisons
    bool equals(const JsonValue* other) const override
    {
        return m_value == static_cast<const Value<tag, T>*>(other)->m_value;
    }
    bool less(const JsonValue* other) const override
    {
        return m_value < static_cast<const Value<tag, T>*>(other)->m_value;
    }

    const T m_value;
    void dump(string& out) const override { json11::dump(m_value, out); }
};

class JsonDouble final : public Value<Json::NUMBER, double>
{
    double number_value() const override { return m_value; }
    int int_value() const override { return static_cast<int>(m_value); }
    bool equals(const JsonValue* other) const override { return m_value == other->number_value(); }
    bool less(const JsonValue* other) const override { return m_value < other->number_value(); }

public:
    explicit JsonDouble(double value)
        : Value(value)
    {
    }
};

class JsonInt final : public Value<Json::NUMBER, int>
{
    double number_value() const override { return m_value; }
    int int_value() const override { return m_value; }
    bool equals(const JsonValue* other) const override { return m_value == other->number_value(); }
    bool less(const JsonValue* other) const override { return m_value < other->number_value(); }

public:
    explicit JsonInt(int value)
        : Value(value)
    {
    }
};

class JsonBoolean final : public Value<Json::BOOL, bool>
{
    bool bool_value() const override { return m_value; }

public:
    explicit JsonBoolean(bool value)
        : Value(value)
    {
    }
};

class JsonString final : public Value<Json::STRING, string>
{
    const string& string_value() const override { return m_value; }

public:
    explicit JsonString(const string& value)
        : Value(value)
    {
    }
    explicit JsonString(string&& value)
        : Value(move(value))
    {
    }
};

class JsonArray final : public Value<Json::ARRAY, Json::array>
{
    const Json::array& array_items() const override { return m_value; }
    const Json& operator[](std::size_t i) const override;

public:
    explicit JsonArray(const Json::array& value)
        : Value(value)
    {
    }
    explicit JsonArray(Json::array&& value)
        : Value(move(value))
    {
    }
};

class JsonObject final : public Value<Json::OBJECT, Json::object>
{
    const Json::object& object_items() const override { return m_value; }
    const Json& operator[](const string& key) const override;

public:
    explicit JsonObject(const Json::object& value)
        : Value(value)
    {
    }
    explicit JsonObject(Json::object&& value)
        : Value(move(value))
    {
    }
};

class JsonNull final : public Value<Json::NUL, NullStruct>
{
public:
    JsonNull()
        : Value({})
    {
    }
};

/* * * * * * * * * * * * * * * * * * * *
 * Static globals - static-init-safe
 */
struct Statics
{
    const std::shared_ptr<JsonValue> null = make_shared<JsonNull>();
    const std::shared_ptr<JsonValue> t = make_shared<JsonBoolean>(true);
    const std::shared_ptr<JsonValue> f = make_shared<JsonBoolean>(false);
    const string empty_string;
    const vector<Json> empty_vector;
    const map<string, Json> empty_map;
    Statics() {}
};

static const Statics& statics()
{
    static const Statics s {};
    return s;
}

static const Json& static_null()
{
    // This has to be separate, not in Statics, because Json() accesses statics().null.
    static const Json json_null;
    return json_null;
}

/* * * * * * * * * * * * * * * * * * * *
 * Constructors
 */

Json::Json() noexcept
    : m_ptr(statics().null)
{
}
Json::Json(std::nullptr_t) noexcept
    : m_ptr(statics().null)
{
}
Json::Json(double value)
    : m_ptr(make_shared<JsonDouble>(value))
{
}
Json::Json(int value)
    : m_ptr(make_shared<JsonInt>(value))
{
}
Json::Json(bool value)
    : m_ptr(value ? statics().t : statics().f)
{
}
Json::Json(const string& value)
    : m_ptr(make_shared<JsonString>(value))
{
}
Json::Json(string&& value)
    : m_ptr(make_shared<JsonString>(move(value)))
{
}
Json::Json(const char* value)
    : m_ptr(make_shared<JsonString>(value))
{
}
Json::Json(const Json::array& values)
    : m_ptr(make_shared<JsonArray>(values))
{
}
Json::Json(Json::array&& values)
    : m_ptr(make_shared<JsonArray>(move(values)))
{
}
Json::Json(const Json::object& values)
    : m_ptr(make_shared<JsonObject>(values))
{
}
Json::Json(Json::object&& values)
    : m_ptr(make_shared<JsonObject>(move(values)))
{
}

/* * * * * * * * * * * * * * * * * * * *
 * Accessors
 */

Json::Type Json::type() const { return m_ptr->type(); }
double Json::number_value() const { return m_ptr->number_value(); }
int Json::int_value() const { return m_ptr->int_value(); }
bool Json::bool_value() const { return m_ptr->bool_value(); }
const string& Json::string_value() const { return m_ptr->string_value(); }
const vector<Json>& Json::array_items() const { return m_ptr->array_items(); }
const map<string, Json>& Json::object_items() const { return m_ptr->object_items(); }
const Json& Json::operator[](std::size_t i) const { return (*m_ptr)[i]; }
const Json& Json::operator[](const string& key) const { return (*m_ptr)[key]; }

double JsonValue::number_value() const { return 0; }
int JsonValue::int_value() const { return 0; }
bool JsonValue::bool_value() const { return false; }
const string& JsonValue::string_value() const { return statics().empty_string; }
const vector<Json>& JsonValue::array_items() const { return statics().empty_vector; }
const map<string, Json>& JsonValue::object_items() const { return statics().empty_map; }
const Json& JsonValue::operator[](std::size_t) const { return static_null(); }
const Json& JsonValue::operator[](const string&) const { return static_null(); }

const Json& JsonObject::operator[](const string& key) const
{
    auto iter = m_value.find(key);
    return (iter == m_value.end()) ? static_null() : iter->second;
}
const Json& JsonArray::operator[](std::size_t i) const
{
    if (i >= m_value.size())
        return static_null();
    else
        return m_value[i];
}

/* * * * * * * * * * * * * * * * * * * *
 * Comparison
 */

bool Json::operator==(const Json& other) const
{
    if (m_ptr == other.m_ptr)
        return true;
    if (m_ptr->type() != other.m_ptr->type())
        return false;

    return m_ptr->equals(other.m_ptr.get());
}

bool Json::operator<(const Json& other) const
{
    if (m_ptr == other.m_ptr)
        return false;
    if (m_ptr->type() != other.m_ptr->type())
        return m_ptr->type() < other.m_ptr->type();

    return m_ptr->less(other.m_ptr.get());
}

/* * * * * * * * * * * * * * * * * * * *
 * Parsing
 */

/* esc(c)
 *
 * Format char c suitable for printing in an error message.
 */
static inline string esc(char c)
{
    char buf[12];
    if (static_cast<std::uint8_t>(c) >= 0x20 && static_cast<std::uint8_t>(c) <= 0x7f)
    {
        snprintf(buf, sizeof buf, "'%c' (%d)", c, c);
    }
    else
    {
        snprintf(buf, sizeof buf, "(%d)", c);
    }
    return string(buf);
}

static inline bool in_range(long x, long lower, long upper)
{
    return (x >= lower && x <= upper);
}

namespace
{
    /* JsonParser
 *
 * Object that tracks all state of an in-progress parse.
 */
    struct JsonParser final
    {

        /* State
     */
        const string& str;
        std::size_t i;
        string& err;
        bool failed;
        const JsonParse strategy;

        /* fail(msg, err_ret = Json())
     *
     * Mark this parse as failed.
     */
        Json fail(string&& msg)
        {
            return fail(move(msg), Json());
        }

        template <typename T>
        T fail(string&& msg, const T err_ret)
        {
            if (!failed)
                err = std::move(msg);
            failed = true;
            return err_ret;
        }

        /* consume_whitespace()
     *
     * Advance until the current character is non-whitespace.
     */
        void consume_whitespace()
        {
            while (str[i] == ' ' || str[i] == '\r' || str[i] == '\n' || str[i] == '\t')
                i++;
        }

        /* consume_comment()
     *
     * Advance comments (c-style inline and multiline).
     */
        bool consume_comment()
        {
            bool comment_found = false;
            if (str[i] == '/')
            {
                i++;
                if (i == str.size())
                    return fail("unexpected end of input after start of comment", false);
                if (str[i] == '/')
                { // inline comment
                    i++;
                    // advance until next line, or end of input
                    while (i < str.size() && str[i] != '\n')
                    {
                        i++;
                    }
                    comment_found = true;
                }
                else if (str[i] == '*')
                { // multiline comment
                    i++;
                    if (i > str.size() - 2)
                        return fail("unexpected end of input inside multi-line comment", false);
                    // advance until closing tokens
                    while (!(str[i] == '*' && str[i + 1] == '/'))
                    {
                        i++;
                        if (i > str.size() - 2)
                            return fail(
                                "unexpected end of input inside multi-line comment", false);
                    }
                    i += 2;
                    comment_found = true;
                }
                else
                    return fail("malformed comment", false);
            }
            return comment_found;
        }

        /* consume_garbage()
     *
     * Advance until the current character is non-whitespace and non-comment.
     */
        void consume_garbage()
        {
            consume_whitespace();
            if (strategy == JsonParse::COMMENTS)
            {
                bool comment_found = false;
                do
                {
                    comment_found = consume_comment();
                    if (failed)
                        return;
                    consume_whitespace();
                } while (comment_found);
            }
        }

        /* get_next_token()
     *
     * Return the next non-whitespace character. If the end of the input is reached,
     * flag an error and return 0.
     */
        char get_next_token()
        {
            consume_garbage();
            if (failed)
                return (char)0;
            if (i == str.size())
                return fail("unexpected end of input", (char)0);

            return str[i++];
        }

        /* encode_utf8(pt, out)
     *
     * Encode pt as UTF-8 and add it to out.
     */
        void encode_utf8(long pt, string& out)
        {
            if (pt < 0)
                return;

            if (pt < 0x80)
            {
                out += static_cast<char>(pt);
            }
            else if (pt < 0x800)
            {
                out += static_cast<char>((pt >> 6) | 0xC0);
                out += static_cast<char>((pt & 0x3F) | 0x80);
            }
            else if (pt < 0x10000)
            {
                out += static_cast<char>((pt >> 12) | 0xE0);
                out += static_cast<char>(((pt >> 6) & 0x3F) | 0x80);
                out += static_cast<char>((pt & 0x3F) | 0x80);
            }
            else
            {
                out += static_cast<char>((pt >> 18) | 0xF0);
                out += static_cast<char>(((pt >> 12) & 0x3F) | 0x80);
                out += static_cast<char>(((pt >> 6) & 0x3F) | 0x80);
                out += static_cast<char>((pt & 0x3F) | 0x80);
            }
        }

        /* parse_string()
     *
     * Parse a string, starting at the current position.
     */
        string parse_string()
        {
            string out;
            long last_escaped_codepoint = -1;
            while (true)
            {
                if (i == str.size())
                    return fail("unexpected end of input in string", "");

                char ch = str[i++];

                if (ch == '"')
                {
                    encode_utf8(last_escaped_codepoint, out);
                    return out;
                }

                if (in_range(ch, 0, 0x1f))
                    return fail("unescaped " + esc(ch) + " in string", "");

                // The usual case: non-escaped characters
                if (ch != '\\')
                {
                    encode_utf8(last_escaped_codepoint, out);
                    last_escaped_codepoint = -1;
                    out += ch;
                    continue;
                }

                // Handle escapes
                if (i == str.size())
                    return fail("unexpected end of input in string", "");

                ch = str[i++];

                if (ch == 'u')
                {
                    // Extract 4-byte escape sequence
                    string esc = str.substr(i, 4);
                    // Explicitly check length of the substring. The following loop
                    // relies on std::string returning the terminating NUL when
                    // accessing str[length]. Checking here reduces brittleness.
                    if (esc.length() < 4)
                    {
                        return fail("bad \\u escape: " + esc, "");
                    }
                    for (std::size_t j = 0; j < 4; j++)
                    {
                        if (!in_range(esc[j], 'a', 'f') && !in_range(esc[j], 'A', 'F')
                            && !in_range(esc[j], '0', '9'))
                            return fail("bad \\u escape: " + esc, "");
                    }

                    long codepoint = strtol(esc.data(), nullptr, 16);

                    // JSON specifies that characters outside the BMP shall be encoded as a pair
                    // of 4-hex-digit \u escapes encoding their surrogate pair components. Check
                    // whether we're in the middle of such a beast: the previous codepoint was an
                    // escaped lead (high) surrogate, and this is a trail (low) surrogate.
                    if (in_range(last_escaped_codepoint, 0xD800, 0xDBFF)
                        && in_range(codepoint, 0xDC00, 0xDFFF))
                    {
                        // Reassemble the two surrogate pairs into one astral-plane character, per
                        // the UTF-16 algorithm.
                        encode_utf8((((last_escaped_codepoint - 0xD800) << 10)
                                        | (codepoint - 0xDC00))
                                + 0x10000,
                            out);
                        last_escaped_codepoint = -1;
                    }
                    else
                    {
                        encode_utf8(last_escaped_codepoint, out);
                        last_escaped_codepoint = codepoint;
                    }

                    i += 4;
                    continue;
                }

                encode_utf8(last_escaped_codepoint, out);
                last_escaped_codepoint = -1;

                if (ch == 'b')
                {
                    out += '\b';
                }
                else if (ch == 'f')
                {
                    out += '\f';
                }
                else if (ch == 'n')
                {
                    out += '\n';
                }
                else if (ch == 'r')
                {
                    out += '\r';
                }
                else if (ch == 't')
                {
                    out += '\t';
                }
                else if (ch == '"' || ch == '\\' || ch == '/')
                {
                    out += ch;
                }
                else
                {
                    return fail("invalid escape character " + esc(ch), "");
                }
            }
        }

        /* parse_number()
     *
     * Parse a double.
     */
        Json parse_number()
        {
            std::size_t start_pos = i;

            if (str[i] == '-')
                i++;

            // Integer part
            if (str[i] == '0')
            {
                i++;
                if (in_range(str[i], '0', '9'))
                    return fail("leading 0s not permitted in numbers");
            }
            else if (in_range(str[i], '1', '9'))
            {
                i++;
                while (in_range(str[i], '0', '9'))
                    i++;
            }
            else
            {
                return fail("invalid " + esc(str[i]) + " in number");
            }

            if (str[i] != '.' && str[i] != 'e' && str[i] != 'E'
                && (i - start_pos) <= static_cast<std::size_t>(std::numeric_limits<int>::digits10))
            {
                return std::atoi(str.c_str() + start_pos);
            }

            // Decimal part
            if (str[i] == '.')
            {
                i++;
                if (!in_range(str[i], '0', '9'))
                    return fail("at least one digit required in fractional part");

                while (in_range(str[i], '0', '9'))
                    i++;
            }

            // Exponent part
            if (str[i] == 'e' || str[i] == 'E')
            {
                i++;

                if (str[i] == '+' || str[i] == '-')
                    i++;

                if (!in_range(str[i], '0', '9'))
                    return fail("at least one digit required in exponent");

                while (in_range(str[i], '0', '9'))
                    i++;
            }

            std::istringstream stm(std::string(str.begin() + start_pos, str.end()));
            stm.imbue(std::locale("C"));
            double result;
            stm >> result;
            return result;
        }

        /* expect(str, res)
     *
     * Expect that 'str' starts at the character that was just read. If it does, advance
     * the input and return res. If not, flag an error.
     */
        Json expect(const string& expected, Json res)
        {
            assert(i != 0);
            i--;
            if (str.compare(i, expected.length(), expected) == 0)
            {
                i += expected.length();
                return res;
            }
            else
            {
                return fail("parse error: expected " + expected + ", got " + str.substr(i, expected.length()));
            }
        }

        /* parse_json()
     *
     * Parse a JSON object.
     */
        Json parse_json(int depth)
        {
            if (depth > max_depth)
            {
                return fail("exceeded maximum nesting depth");
            }

            char ch = get_next_token();
            if (failed)
                return Json();

            if (ch == '-' || (ch >= '0' && ch <= '9'))
            {
                i--;
                return parse_number();
            }

            if (ch == 't')
                return expect("true", true);

            if (ch == 'f')
                return expect("false", false);

            if (ch == 'n')
                return expect("null", Json());

            if (ch == '"')
                return parse_string();

            if (ch == '{')
            {
                map<string, Json> data;
                ch = get_next_token();
                if (ch == '}')
                    return data;

                while (1)
                {
                    if (ch != '"')
                        return fail("expected '\"' in object, got " + esc(ch));

                    string key = parse_string();
                    if (failed)
                        return Json();

                    ch = get_next_token();
                    if (ch != ':')
                        return fail("expected ':' in object, got " + esc(ch));

                    data[std::move(key)] = parse_json(depth + 1);
                    if (failed)
                        return Json();

                    ch = get_next_token();
                    if (ch == '}')
                        break;
                    if (ch != ',')
                        return fail("expected ',' in object, got " + esc(ch));

                    ch = get_next_token();
                }
                return data;
            }

            if (ch == '[')
            {
                vector<Json> data;
                ch = get_next_token();
                if (ch == ']')
                    return data;

                while (1)
                {
                    i--;
                    data.push_back(parse_json(depth + 1));
                    if (failed)
                        return Json();

                    ch = get_next_token();
                    if (ch == ']')
                        break;
                    if (ch != ',')
                        return fail("expected ',' in list, got " + esc(ch));

                    ch = get_next_token();
                    (void)ch;
                }
                return data;
            }

            return fail("expected value, got " + esc(ch));
        }
    };
} //namespace {

Json Json::parse(const string& in, string& err, JsonParse strategy)
{
    JsonParser parser {in, 0, err, false, strategy};
    Json result = parser.parse_json(0);

    // Check for any trailing garbage
    parser.consume_garbage();
    if (parser.failed)
        return Json();
    if (parser.i != in.size())
        return parser.fail("unexpected trailing " + esc(in[parser.i]));

    return result;
}

// Documented in json11.hpp
vector<Json> Json::parse_multi(const string& in,
    std::string::size_type& parser_stop_pos,
    string& err,
    JsonParse strategy)
{
    JsonParser parser {in, 0, err, false, strategy};
    parser_stop_pos = 0;
    vector<Json> json_vec;
    while (parser.i != in.size() && !parser.failed)
    {
        json_vec.push_back(parser.parse_json(0));
        if (parser.failed)
            break;

        // Check for another object
        parser.consume_garbage();
        if (parser.failed)
            break;
        parser_stop_pos = parser.i;
    }
    return json_vec;
}

/* * * * * * * * * * * * * * * * * * * *
 * Shape-checking
 */

bool Json::has_shape(const shape& types, string& err) const
{
    if (!is_object())
    {
        err = "expected JSON object, got " + dump();
        return false;
    }

    for (auto& item : types)
    {
        if ((*this)[item.first].type() != item.second)
        {
            err = "bad type for " + item.first + " in " + dump();
            return false;
        }
    }

    return true;
}

} // namespace json11