#include <cstdint>

#include "commons/commons_byteparser.h"
#include "commons/commons_base.h"
#include "commons/commons_json_parser.h"
#include "commons/commons_json_value.h"
#include "commons/commons_stringparser.h"

static auto PushOut(json_parser& self, const json_value& value) -> json_value*
{
    if (self.outSize == 0)
        return nullptr;

    json_value* ret = self.out;
    *ret = value;

    ++self.out;
    --self.outSize;

    return ret;
}

static auto ParseLiteral(json_parser& self) -> json_value*
{
    switch (ByteParser_Read(self)) {
    case 'n': {
        if (!ByteParser_HasNext(self) || ByteParser_Read(self) != 'u' || !ByteParser_HasNext(self) || ByteParser_Read(self) != 'l' || !ByteParser_HasNext(self) || ByteParser_Read(self) != 'l')
            return nullptr;

        json_value val;
        JsonValue_SetValue(val, json_tag::Null);
        return PushOut(self, val);
    }

    case 't': {
        if (!ByteParser_HasNext(self) || ByteParser_Read(self) != 'r' || !ByteParser_HasNext(self) || ByteParser_Read(self) != 'u' || !ByteParser_HasNext(self) || ByteParser_Read(self) != 'e')
            return nullptr;

        json_value val;
        JsonValue_SetValue(val, true);

        return PushOut(self, val);
    }

    case 'f': {
        if (!ByteParser_HasNext(self) || ByteParser_Read(self) != 'a' || !ByteParser_HasNext(self) || ByteParser_Read(self) != 'l' || !ByteParser_HasNext(self) || ByteParser_Read(self) != 's' || !ByteParser_HasNext(self) || ByteParser_Read(self) != 'e')
            return nullptr;

        json_value val;
        JsonValue_SetValue(val, false);

        return PushOut(self, val);
    }

    default: {
        return nullptr;
    }
    }
}

static auto ParseNumber(json_parser& self) -> json_value*
{
    double doubleVal;
    int64_t longVal;

    json_value val;
    switch (StringParser_ParseDecimal(self, doubleVal, longVal)) {
    case StringParser_ParseNumberResult::Double: {
        JsonValue_SetValue(val, doubleVal);
        break;
    }
    case StringParser_ParseNumberResult::Long: {
        JsonValue_SetValue(val, longVal);
        break;
    }
    }

    return PushOut(self, val);
}

static auto ParseString(json_parser& self) -> json_value*
{
    const uint8_t* base = self.at;
    uint64_t count = 0;
    bool closed = false;

    while (ByteParser_HasNext(self)) {
        const uint8_t ch = ByteParser_Read(self);
        if (ch == '"') {
            closed = true;
            break;
        }

        ++count;

        // Skip escaped character — backslash escapes the next char
        if (ch == '\\' && ByteParser_HasNext(self)) {
            ByteParser_Read(self);
            ++count;
        }
    }

    if (!closed)
        return nullptr;

    json_value val;
    JsonValue_SetValue(val, byteview { base, count });

    return PushOut(self, val);
}

static auto ParseArray(json_parser& self) -> json_value*
{
    json_value* begin = PushOut(self, json_value());
    if (!begin)
        return nullptr;

    int32_t count = 0;

    for (;;) {
        if (!ByteParser_HasNext(self))
            return nullptr;
        if (ByteParser_Peek(self) == ']') {
            ByteParser_Advance(self);
            break;
        }

        ++count;

        json_value* elem = JsonParser_ParseNext(self);
        if (!elem)
            return nullptr;

        StringParser_SkipWhitespace(self);
        if (!ByteParser_HasNext(self))
            return nullptr;
        const uint8_t ch = ByteParser_Read(self);
        if (ch == ']')
            break;

        if (ch != ',')
            return nullptr;
    }

    json_value* end = PushOut(self, json_value());
    if (!end)
        return nullptr;

    JsonValue_SetValue(*begin, json_tag::ArrayBegin, count, end);
    JsonValue_SetValue(*end, json_tag::ArrayEnd);

    return begin;
}

static auto ParseObject(json_parser& self) -> json_value*
{
    auto* begin = PushOut(self, json_value { });
    if (!begin)
        return nullptr;

    uint32_t count = 0;

    for (;;) {
        if (!ByteParser_HasNext(self))
            return nullptr;
        if (ByteParser_Peek(self) == '}') {
            ByteParser_Advance(self);
            break;
        }

        ++count;

        json_value* key = JsonParser_ParseNext(self);
        if (!key || key->tag != json_tag::String)
            return nullptr;

        StringParser_SkipWhitespace(self);
        if (!ByteParser_HasNext(self) || ByteParser_Read(self) != ':')
            return nullptr;

        json_value* val = JsonParser_ParseNext(self);
        if (!val)
            return nullptr;

        StringParser_SkipWhitespace(self);
        if (!ByteParser_HasNext(self))
            return nullptr;
        const uint8_t ch = ByteParser_Read(self);
        if (ch == '}')
            break;

        if (ch != ',')
            return nullptr;
    }

    json_value* end = PushOut(self, json_value());
    if (!end)
        return nullptr;

    JsonValue_SetValue(*begin, json_tag::ObjectBegin, count, end);
    JsonValue_SetValue(*end, json_tag::ObjectEnd);

    return begin;
}

auto API JsonParser_ParseNext(json_parser& self) -> json_value*
{
    StringParser_SkipWhitespace(self);

    if (!ByteParser_HasNext(self))
        return nullptr;

    uint8_t ch = ByteParser_Peek(self);
    if (IsNumber(ch) || ch == '-')
        return ParseNumber(self);
    if (IsAlpha(ch))
        return ParseLiteral(self);

    if (!ByteParser_HasNext(self))
        return nullptr;
    ByteParser_Advance(self);
    if (ch == '"')
        return ParseString(self);
    if (ch == '[')
        return ParseArray(self);
    if (ch == '{')
        return ParseObject(self);

    return nullptr;
}