#include "../include/VersionParser.hpp"
#include "../include/StringView.hpp"

namespace sibs
{
    static int stringToIntNoVerify(const StringView &str)
    {
        int result = 0;
        for(usize i = 0; i < str.size; ++i)
        {
            result = (result * 10) + (str[i] - '0');
        }
        return result;
    }
    
    static bool isNum(char c)
    {
        return c >= '0' && c <= '9';
    }
    
    static bool isAlpha(char c)
    {
        return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');
    }

    Result<PackageVersion> parsePackageVersion(const StringView &versionStr, int *size)
    {
        PackageVersion result = { 0, 0, 0 };
        int *versionPtr = &result.major;
        int digitStart = 0;
        int i = 0;

        for(; i < (int)versionStr.size; ++i)
        {
            char c = versionStr[i];
            if(isNum(c))
            {
                if(digitStart == -1)
                    digitStart = i;
            }
            else
            {
                int length = i - digitStart;
                if(digitStart == -1 || length == 0)
                    return Result<PackageVersion>::Err("Package version string is in invalid format. Expected to be in format xxx.xxx.xxx where x is a number");

                *versionPtr = stringToIntNoVerify({ versionStr.data + digitStart, (usize)(i - digitStart) });
                bool endOfVersions = versionPtr == &result.patch;
                ++versionPtr;
                digitStart = -1;

                if(c != '.' || endOfVersions)
                    break;
            }
        }

        if(i == 0)
            return Result<PackageVersion>::Err("version can't be empty");

        if(digitStart != -1)
        {
            *versionPtr = stringToIntNoVerify({ versionStr.data + digitStart, (usize)(i - digitStart) });
            ++versionPtr;
        }

        if(size)
            *size = i;

        if(versionPtr == &result.major)
            return Result<PackageVersion>::Err("version can't be empty");

        return Result<PackageVersion>::Ok(result);
    }

    VersionTokenizer::VersionTokenizer() : 
        start(nullptr),
        code(nullptr),
        size(0),
        index(0)
    {

    }

    VersionTokenizer::VersionTokenizer(const char *_start, const usize _size) : 
        start(_start),
        code(_start),
        size(_size),
        index(0)
    {

    }

    VersionTokenizer::VersionTokenizer(const VersionTokenizer &other)
    {
        start = other.start;
        code = other.code;
        size = other.size;
        index = other.index;
    }

    VersionToken VersionTokenizer::next()
    {
        while(index < size)
        {
            char c = code[index];
            if(c == ' ' || c == '\t' || c == '\n' || c == '\r')
                ++index;
            else
                break;
        }

        if(index >= size)
            return VersionToken::END_OF_FILE;

        char c = code[index];
        if(isNum(c))
        {
            int versionStrSize = 0;
            identifier.data = code + index;
            Result<PackageVersion> packageVersion = parsePackageVersion({ code + index, (usize)(size - index) }, &versionStrSize);
            identifier.size = versionStrSize;
            index += versionStrSize;
            if(!packageVersion)
            {
                errMsg = packageVersion.getErrMsg();
                return VersionToken::INVALID;
            }
            version = packageVersion.unwrap();
            return VersionToken::VERSION_NUMBER;
        }
        else if(isAlpha(c))
        {
            usize identifierStart = index;
            ++index;
            while(index < size && isAlpha(code[index]))
            {
                ++index;
            }
            usize identifierEnd = index;
            usize identifierLength = identifierEnd - identifierStart;
            
            if(identifierLength == 3 && strncmp(code + identifierStart, "and", 3) == 0)
            {
                return VersionToken::AND;
            }
            else
            {
                errMsg = "Invalid identifier ";
                errMsg += std::string(code + identifierStart, identifierLength);
                return VersionToken::INVALID;
            }
        }
        else if(c == '<')
        {
            ++index;
            if(index < size && code[index] == '=')
            {
                ++index;
                operation = VersionOperation::LESS_EQUAL;
                return VersionToken::OPERATION;
            }
            operation = VersionOperation::LESS;
            return VersionToken::OPERATION;
        }
        else if(c == '=')
        {
            ++index;
            operation = VersionOperation::EQUAL;
            return VersionToken::OPERATION;
        }
        else if(c == '>')
        {
            ++index;
            if(index < size && code[index] == '=')
            {
                ++index;
                operation = VersionOperation::GREATER_EQUAL;
                return VersionToken::OPERATION;
            }
            operation = VersionOperation::GREATER;
            return VersionToken::OPERATION;
        }
        else
        {
            errMsg = "Unexpected character ";
            errMsg += c;
            return VersionToken::INVALID;
        }
    }

    Result<PackageVersionRange> VersionParser::parse(const char *code, const usize size)
    {
        versionRange = PackageVersionRange();
        tokenizer = VersionTokenizer(code, size);
        VersionToken token = parseStart();

        if(token == VersionToken::END_OF_FILE)
        {
            if(!versionRange.startDefined)
                return Result<PackageVersionRange>::Err("version can't be empty");
            
            if(versionRange.startOperation == VersionOperation::NONE)
            {
                versionRange.startOperation = VersionOperation::GREATER_EQUAL;
                versionRange.end.major = versionRange.start.major + 1;
                versionRange.end.minor = 0;
                versionRange.end.patch = 0;
                versionRange.endOperation = VersionOperation::LESS;
                versionRange.endDefined = true;
            }
            return Result<PackageVersionRange>::Ok(versionRange);
        }
        else if(token == VersionToken::INVALID)
            return Result<PackageVersionRange>::Err(tokenizer.errMsg);
        else
        {
            std::string errMsg = "Unexpected token '";
            switch(token)
            {
                case VersionToken::NONE:
                {
                    errMsg += "<none>";
                    break;
                }
                case VersionToken::OPERATION:
                {
                    errMsg += "operation ";
                    errMsg += asString(tokenizer.operation);
                    break;
                }
                case VersionToken::AND:
                {
                    errMsg += "and";
                    break;
                }
                case VersionToken::VERSION_NUMBER:
                {
                    errMsg += "version ";
                    errMsg += std::string(tokenizer.identifier.data, tokenizer.identifier.size);
                    break;
                }
                default:
                    break;
            }
            errMsg += "'";
            return Result<PackageVersionRange>::Err(errMsg);
        }
    }

    VersionToken VersionParser::parseStart()
    {
        VersionToken token = tokenizer.next();
        if(token == VersionToken::VERSION_NUMBER)
        {
            versionRange.startOperation = VersionOperation::NONE;
            versionRange.start = tokenizer.version;
            versionRange.startDefined = true;
            token = tokenizer.next();
            if(token == VersionToken::AND)
            {
                token = VersionToken::INVALID;
                tokenizer.errMsg = "Unexpected end version when start version does not have operation defined";
            }
        }
        else if(token == VersionToken::OPERATION)
        {
            versionRange.startOperation = tokenizer.operation;
            token = tokenizer.next();
            if(token == VersionToken::VERSION_NUMBER)
            {
                versionRange.start = tokenizer.version;
                versionRange.startDefined = true;
                switch(versionRange.startOperation)
                {
                    case VersionOperation::LESS:
                    {
                        token = VersionToken::INVALID;
                        tokenizer.errMsg = "Unexpected version end when start version is expected to less than ";
                        tokenizer.errMsg += versionRange.start.toString();
                        return token;
                    }
                    case VersionOperation::LESS_EQUAL:
                    {
                        token = VersionToken::INVALID;
                        tokenizer.errMsg = "Unexpected version end when start version is expected to be less or equal to ";
                        tokenizer.errMsg += versionRange.start.toString();
                        return token;
                    }
                    case VersionOperation::EQUAL:
                    {
                        token = VersionToken::INVALID;
                        tokenizer.errMsg = "Unexpected version end when start version is expected to be exactly ";
                        tokenizer.errMsg += versionRange.start.toString();
                        return token;
                    }
                    default:
                        break;
                }
                
                token = tokenizer.next();
                if(token == VersionToken::AND)
                {
                    return parseEnd();
                }
            }
            else if(token == VersionToken::INVALID)
                return token;
            else
            {
                token = VersionToken::INVALID;
                tokenizer.errMsg = "Expected version after operation";
            }
        }
        return token;
    }

    VersionToken VersionParser::parseEnd()
    {
        VersionToken token = tokenizer.next();
        if(token == VersionToken::OPERATION)
        {
            versionRange.endOperation = tokenizer.operation;
            switch(versionRange.endOperation)
            {
                case VersionOperation::EQUAL:
                case VersionOperation::GREATER:
                case VersionOperation::GREATER_EQUAL:
                {
                    token = VersionToken::INVALID;
                    tokenizer.errMsg = "End version can only have operations < and <=";
                    return token;
                }
                default:
                    break;
            }

            token = tokenizer.next();
            if(token == VersionToken::VERSION_NUMBER)
            {
                versionRange.end = tokenizer.version;
                versionRange.endDefined = true;
                if(versionRange.end <= versionRange.start)
                {
                    token = VersionToken::INVALID;
                    tokenizer.errMsg = "Expected version end to be greater than ";
                    tokenizer.errMsg += versionRange.start.toString();
                    tokenizer.errMsg += ", was ";
                    tokenizer.errMsg += versionRange.end.toString();
                    return token;
                }
                token = tokenizer.next();
            }
            else if(token == VersionToken::INVALID)
                return token;
            else
            {
                token = VersionToken::INVALID;
                tokenizer.errMsg = "Expected version after operation";
            }
        }
        else
        {
            token = VersionToken::INVALID;
            tokenizer.errMsg = "Expected end version to have operation defined";
        }
        return token;
    }
}