#include "Lexer.hpp"
#include <cmath>
#include <stdexcept>
#include "NumericalLexers.hpp"

namespace ElohimScript::Parser {
    const LexToken* Lexer::Lex() {
        auto* first = LexNext();
        if (first->GetKind() == LexTokenKind::EndOfFile) {
            return first;
        }
        auto* last = first;
        while (true) {
            auto* next = LexNext();
            last->_next = std::unique_ptr<const LexToken>(next);
            last = next;
            if (next->GetKind() == LexTokenKind::EndOfFile) {
                break;
            }
        }
        return first;
    }

    LexToken* Lexer::LexNext() {
        auto c = Consume();
        switch (c) {
            case u8'\0': return new LexTokenImpl<LexTokenKind::EndOfFile>();
            case u8'*': {
                auto n = Peek();
                if (n == u8'*') {
                    Progress();
                    n = Peek();
                    if (n == u8'=') {
                        Progress();
                        return new LexTokenImpl<LexTokenKind::StarStarEqualsSymbol>();
                    }
                    return new LexTokenImpl<LexTokenKind::StarStarSymbol>();
                }
                if (n == u8'=') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::StarEqualsSymbol>();
                }
                return new LexTokenImpl<LexTokenKind::StarSymbol>();
            }
            case u8'/':
                if (Peek() == u8'=') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::SlashEqualsSymbol>();
                }
                return new LexTokenImpl<LexTokenKind::SlashSymbol>();
            case u8'%':
                if (Peek() == u8'=') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::PercentEqualsSymbol>();
                }
                return new LexTokenImpl<LexTokenKind::PercentSymbol>();
            case u8'+': {
                auto n = Peek();
                if (n == u8'=') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::PlusEqualsSymbol>();
                }
                if (n == u8'+') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::PlusPlusSymbol>();
                }
                return new LexTokenImpl<LexTokenKind::PlusSymbol>();
            }
            case u8'-': {
                auto n = Peek();
                if (n == u8'=') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::MinusEqualsSymbol>();
                }
                if (n == u8'-') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::MinusMinusSymbol>();
                }
                return new LexTokenImpl<LexTokenKind::MinusSymbol>();
            }
            case u8'<': {
                auto n = Peek();
                if (n == u8'=') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::LessThanEqualsSymbol>();
                }
                if (n == u8'<') {
                    Progress();
                    if (Peek() == u8'=') {
                        Progress();
                        return new LexTokenImpl<LexTokenKind::LessThanLessThanEqualsSymbol>();
                    }
                    return new LexTokenImpl<LexTokenKind::LessThanLessThanSymbol>();
                }
                return new LexTokenImpl<LexTokenKind::LessThanSymbol>();
            }
            case u8'>': {
                auto n = Peek();
                if (n == u8'=') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::GreaterThanEqualsSymbol>();
                }
                if (n == u8'>') {
                    Progress();
                    n = Peek();
                    if (n == u8'=') {
                        Progress();
                        return new LexTokenImpl<LexTokenKind::GreaterThanGreaterThanEqualsSymbol>();
                    }
                    if (n == u8'>') {
                        Progress();
                        if (Peek() == u8'=') {
                            Progress();
                            return new LexTokenImpl<LexTokenKind::GreaterThanGreaterThanGreaterThanEqualsSymbol>();
                        }
                        return new LexTokenImpl<LexTokenKind::GreaterThanGreaterThanGreaterThanSymbol>();
                    }
                    return new LexTokenImpl<LexTokenKind::GreaterThanGreaterThanSymbol>();
                }
                return new LexTokenImpl<LexTokenKind::GreaterThanSymbol>();
            }
            case u8'(': return new LexTokenImpl<LexTokenKind::OpenParenthesisSymbol>();
            case u8')': return new LexTokenImpl<LexTokenKind::CloseParenthesisSymbol>();
            case u8'=': {
                if (Peek() == u8'=') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::EqualsEqualsSymbol>();
                }
                return new LexTokenImpl<LexTokenKind::EqualsSymbol>();
            }
            case u8'!': {
                auto n = Peek();
                if (n == u8'=') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::ExclamationMarkEqualsSymbol>();
                }
                if (n == u8'i' && Peek(2) == u8's') {
                    Progress(2);
                    return new LexTokenImpl<LexTokenKind::ExclamationMarkIsSymbol>();
                }
                return new LexTokenImpl<LexTokenKind::ExclamationMarkSymbol>();
            }
            case u8'?': return new LexTokenImpl<LexTokenKind::QuestionMarkSymbol>();
            case u8':': {
                if (Peek() == u8':') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::ColonColonSymbol>();
                }
                return new LexTokenImpl<LexTokenKind::ColonSymbol>();
            }
            case u8'&': {
                auto n = Peek();
                if (n == u8'=') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::AmpersandEqualsSymbol>();
                }
                if (n == u8'&') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::AmpersandAmpersandSymbol>();
                }
                return new LexTokenImpl<LexTokenKind::AmpersandSymbol>();
            }
            case u8',': return new LexTokenImpl<LexTokenKind::CommaSymbol>();
            case u8'{': return new LexTokenImpl<LexTokenKind::OpenCurlyParenthesisSymbol>();
            case u8'}': return new LexTokenImpl<LexTokenKind::CloseCurlyParenthesisSymbol>();
            case u8';': return new LexTokenImpl<LexTokenKind::SemicolonSymbol>();
            case u8'|': {
                auto n = Peek();
                if (n == u8'=') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::VerticalLineEqualsSymbol>();
                }
                if (n == u8'|') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::VerticalLineVerticalLineSymbol>();
                }
                return new LexTokenImpl<LexTokenKind::VerticalLineSymbol>();
            }
            case u8'^': {
                auto n = Peek();
                if (n == u8'=') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::CaretEqualsSymbol>();
                }
                if (n == u8'^') {
                    Progress();
                    return new LexTokenImpl<LexTokenKind::CaretCaretSymbol>();
                }
                return new LexTokenImpl<LexTokenKind::CaretSymbol>();
            }
            case u8'~': return new LexTokenImpl<LexTokenKind::TildeSymbol>();
            case u8'.': return new LexTokenImpl<LexTokenKind::DotSymbol>();
            case u8'[': return new LexTokenImpl<LexTokenKind::OpenBlockParenthesisSymbol>();
            case u8']': return new LexTokenImpl<LexTokenKind::CloseBlockParenthesisSymbol>();
            case u8'@': return new LexTokenImpl<LexTokenKind::AtSymbol>();

            case u8' ':
            case u8'\r':
            case u8'\n':
            case u8'\t': return new LexTokenImpl<LexTokenKind::Whitespace>();
            // Byte order mark
            case u8'\xEF': {
                if (Peek() == u8'\xBB' && Peek(2) == u8'\xBF') {
                    Progress(2);
                    return new LexTokenImpl<LexTokenKind::Whitespace>();
                }
            }
            case u8'0':
            case u8'1':
            case u8'2':
            case u8'3':
            case u8'4':
            case u8'5':
            case u8'6':
            case u8'7':
            case u8'8':
            case u8'9': return LexNumerical(c);
            case u8'\'': return LexString(u8'\'', false);
            case u8'"': {
                if (Peek() == '"' && Peek(2) == '\"') {
                    return LexString(u8'"', true);
                }
                return LexString(u8'"', false);
            }

            default: return new LexTokenImpl<LexTokenKind::Unknown>();
        }
    }

    LexToken* Lexer::LexNumerical(char8_t c) {
        auto initialValue = LexDecimalValue(c);
        auto numericalSystem = 10; // Default to decimal system.
        if (initialValue == 0) {
            auto secondChar = Peek();
            auto secondValue = LexDecimalValue(secondChar);
            if (secondChar != '.' && secondValue == 255) {
                Progress();
                switch (secondChar) {
                    case 'x': numericalSystem = 16; break;
                    case 'd': numericalSystem = 10; break;
                    case 'o':
                        numericalSystem = 8;
                        break;
                        ;
                    case 'b': numericalSystem = 2; break;
                    default:
                        // TODO: Log Invalid numerical system
                        break;
                }
            }
        }
        switch (numericalSystem) {
            case 10: return LexDecimal(initialValue);
            case 16: return LexHexadecimal();
            case 8: return LexOctal();
            case 2: return LexBinary();
            default: throw std::logic_error("Not implemented");
        }
    }

    constexpr int64_t quick_pow10(int n) {
        constexpr int64_t pow10[20] = {1,
                                       10,
                                       100,
                                       1000,
                                       10000,
                                       100000,
                                       1000000,
                                       10000000,
                                       100000000,
                                       1000000000,
                                       10000000000,
                                       100000000000,
                                       1000000000000,
                                       10000000000000,
                                       10000000000000,
                                       100000000000000,
                                       1000000000000000,
                                       10000000000000000,
                                       100000000000000000,
                                       1000000000000000000};
        return pow10[n];
    }

    LexToken* Lexer::LexDecimal(uint64_t initial) {
        uint64_t value = initial;
        uint64_t decimalValue = 0;
        uint64_t exponentValue = 0;
        uint8_t decimalLength = 0;
        bool isDecimal = false;
        bool isExponent = false;
        while (true) {
            auto v = (uint64_t)LexDecimalValue(Peek());
            if (v == 255) {
                if (!isDecimal && Peek() == u8'.') {
                    isDecimal = true;
                    Progress();
                    continue;
                }
                if (isDecimal && (Peek() == u8'e' || Peek() == u8'E')) {
                    isDecimal = false;
                    isExponent = true;
                    Progress();
                    continue;
                }
                break;
            }
            Progress();
            if (isDecimal) {
                decimalValue *= 10;
                decimalValue += v;
                decimalLength++;
            } else if (isExponent) {
                exponentValue *= 10;
                exponentValue += v;
            } else {
                value *= 10;
                value += v;
            }
        }
        if (isDecimal || isExponent) {
            auto val = value + ((double)decimalValue / quick_pow10(decimalLength));
            if (isExponent) {
                val *= pow(10, exponentValue);
            }
            return new FloatLiteral(val);
        }
        return new IntegerLiteral(value);
    }

    IntegerLiteral* Lexer::LexHexadecimal() {
        uint64_t value = 0;
        while (true) {
            auto v = LexHexadecimalValue(Peek());
            if (v == 255) {
                break;
            }
            Progress();
            value <<= 4;
            value += v;
        }
        return new IntegerLiteral(value);
    }
    IntegerLiteral* Lexer::LexOctal() {
        uint64_t value = 0;
        while (true) {
            auto v = LexOctalValue(Peek());
            if (v == 255) {
                break;
            }
            Progress();
            value <<= 3;
            value += v;
        }
        return new IntegerLiteral(value);
    }
    IntegerLiteral* Lexer::LexBinary() {
        uint64_t value = 0;
        while (true) {
            auto v = LexBinaryValue(Peek());
            if (v == 255) {
                break;
            }
            Progress();
            value <<= 1;
            value += v;
        }
        return new IntegerLiteral(value);
    }
    StringLiteral* Lexer::LexString(char8_t opening, bool heredoc) {
        Progress();
        if (heredoc) {
            Progress(2);
        }
        auto start = _position;
        size_t offset = 0;
        while (true) {
            auto current = Peek(offset);
            if (heredoc) {
                if (current == '"' && Peek(offset + 1) == '"' && Peek(offset + 2) == '"' && Peek(offset + 3) != '"') {
                    break;
                }
            } else if (current == opening) {
                break;
            }
            if (current == u8'\0') {
                // TODO: Log error
                break;
            }
            if (!heredoc && (current == u8'\n' || current == u8'\r')) {
                // TODO: log error
                break;
            }
            offset++;
        }
        Progress(offset);
        if (heredoc) {
            Progress(2);
        }
        return new StringLiteral(std::u8string(_script.substr(start, offset)));
    }
}