#include "kappa/dsl/lexer.hpp"

#include <cctype>
#include <stdexcept>
#include <unordered_map>

namespace kappa::dsl {

static const std::unordered_map<std::string_view, TokenType> keywords = {
    {"package",  TokenType::KwPackage},
    {"version",  TokenType::KwVersion},
    {"source",   TokenType::KwSource},
    {"depends",  TokenType::KwDepends},
    {"provides", TokenType::KwProvides},
    {"outputs",   TokenType::KwOutputs},
    {"conflicts", TokenType::KwConflicts},
    {"features",  TokenType::KwFeatures},
    {"config",   TokenType::KwConfig},
    {"const",    TokenType::KwConst},
    {"license",  TokenType::KwLicense},
    {"patches",  TokenType::KwPatches},
    {"env",      TokenType::KwEnv},
    {"service",  TokenType::KwService},
    {"sha256",   TokenType::KwSha256},
    {"sha512",   TokenType::KwSha512},
    {"md5",      TokenType::KwMd5},
    {"assert",   TokenType::KwAssert},
    {"import",   TokenType::KwImport},
    {"prepare",  TokenType::KwPrepare},
    {"build",    TokenType::KwBuild},
    {"check",    TokenType::KwCheck},
    {"install",  TokenType::KwInstall},
    {"uninstall", TokenType::KwUninstall},
    {"true",     TokenType::KwTrue},
    {"false",    TokenType::KwFalse},
    {"index",    TokenType::KwIndex},
    {"repos",    TokenType::KwRepos},
};

std::string_view token_name(TokenType type) {
    switch (type) {
    case TokenType::Eof:       return "EOF";
    case TokenType::Newline:   return "newline";
    case TokenType::Lbrace:    return "{";
    case TokenType::Rbrace:    return "}";
    case TokenType::Equals:    return "=";
    case TokenType::Plus:      return "+";
    case TokenType::Lbracket:  return "[";
    case TokenType::Rbracket:  return "]";
    case TokenType::Comma:     return ",";
    case TokenType::String:    return "string";
    case TokenType::Ident:     return "ident";
    case TokenType::KwPackage:  return "package";
    case TokenType::KwVersion:  return "version";
    case TokenType::KwSource:   return "source";
    case TokenType::KwDepends:  return "depends";
    case TokenType::KwProvides: return "provides";
    case TokenType::KwOutputs:  return "outputs";
    case TokenType::KwConflicts: return "conflicts";
    case TokenType::KwFeatures: return "features";
    case TokenType::KwConfig:   return "config";
    case TokenType::KwConst:    return "const";
    case TokenType::KwLicense:  return "license";
    case TokenType::KwPatches:  return "patches";
    case TokenType::KwEnv:      return "env";
    case TokenType::KwService:  return "service";
    case TokenType::KwSha256:   return "sha256";
    case TokenType::KwSha512:   return "sha512";
    case TokenType::KwMd5:      return "md5";
    case TokenType::KwAssert:   return "assert";
    case TokenType::KwImport:   return "import";
    case TokenType::KwPrepare:  return "prepare";
    case TokenType::KwBuild:    return "build";
    case TokenType::KwCheck:    return "check";
    case TokenType::KwInstall:  return "install";
    case TokenType::KwUninstall: return "uninstall";
    case TokenType::KwTrue:     return "true";
    case TokenType::KwFalse:    return "false";
    case TokenType::KwIndex:    return "index";
    case TokenType::KwRepos:    return "repos";
    }
    return "?";
}

Lexer::Lexer(std::string_view source) : source_(source) {}

char Lexer::peek() const {
    return pos_ < source_.size() ? source_[pos_] : '\0';
}

char Lexer::advance() {
    if (pos_ >= source_.size()) { return '\0'; }
    char c = source_[pos_++];
    if (c == '\n') { ++line_; col_ = 1; }
    else           { ++col_; }
    return c;
}

bool Lexer::match(char c) {
    if (peek() == c) { advance(); return true; }
    return false;
}

void Lexer::skip_whitespace() {
    while (std::isspace(static_cast<unsigned char>(peek())) && peek() != '\n') {
        advance();
    }
}

bool Lexer::skip_comment() {
    if (peek() != '/') { return false; }
    if (pos_ + 1 >= source_.size()) { return false; }

    char next = source_[pos_ + 1];
    if (next == '/') {
        advance(); advance(); // skip //
        while (pos_ < source_.size() && peek() != '\n') { advance(); }
        return true;
    }
    if (next == '*') {
        advance(); advance(); // skip /*
        while (pos_ + 1 < source_.size()) {
            if (peek() == '*' && source_[pos_ + 1] == '/') {
                advance(); advance(); // skip */
                return true;
            }
            advance();
        }
        return true; // unterminated — consume to EOF
    }
    return false;
}

Token Lexer::next() {
    while (true) {
        skip_whitespace();
        if (skip_comment()) { continue; }

        token_start_line_ = line_;
        token_start_col_  = col_;

        if (pos_ >= source_.size()) { return {TokenType::Eof, "", line_, col_}; }

        char c = peek();

        if (c == '\n') {
            advance();
            return {TokenType::Newline, "\n", token_start_line_, token_start_col_};
        }
        if (c == '"') { return scan_string(); }
        if (c == '{' || c == '}' || c == '=' || c == '+' || c == '[' || c == ']' || c == ',') {
            return scan_symbol();
        }
        return scan_ident();
    }
}

Token Lexer::scan_ident() {
    std::string lexeme;
    while (pos_ < source_.size()) {
        char c = peek();
        if (std::isspace(static_cast<unsigned char>(c))) { break; }
        if (c == '"' || c == '=' || c == '+' || c == '[' || c == ']' || c == ',') { break; }
        lexeme += advance();
    }

    auto it = keywords.find(lexeme);
    if (it != keywords.end()) {
        return {it->second, lexeme, token_start_line_, token_start_col_};
    }
    return {TokenType::Ident, lexeme, token_start_line_, token_start_col_};
}

Token Lexer::scan_string() {
    advance(); // opening "
    std::string lexeme;
    while (pos_ < source_.size()) {
        char c = peek();
        if (c == '"') { advance(); break; }
        if (c == '\\') {
            advance();
            if (pos_ < source_.size()) {
                char esc = advance();
                switch (esc) {
                case 'n':  lexeme += '\n'; break;
                case 't':  lexeme += '\t'; break;
                case '\\': lexeme += '\\'; break;
                case '"':  lexeme += '"';  break;
                default:   lexeme += esc;  break;
                }
            }
        } else {
            lexeme += advance();
        }
    }
    return {TokenType::String, lexeme, token_start_line_, token_start_col_};
}

Token Lexer::scan_symbol() {
    char c = advance();
    switch (c) {
    case '{': return {TokenType::Lbrace,   "{", token_start_line_, token_start_col_};
    case '}': return {TokenType::Rbrace,   "}", token_start_line_, token_start_col_};
    case '=': return {TokenType::Equals,   "=", token_start_line_, token_start_col_};
    case '+': return {TokenType::Plus,     "+", token_start_line_, token_start_col_};
    case '[': return {TokenType::Lbracket, "[", token_start_line_, token_start_col_};
    case ']': return {TokenType::Rbracket, "]", token_start_line_, token_start_col_};
    case ',': return {TokenType::Comma,    ",", token_start_line_, token_start_col_};
    default:  return {TokenType::Eof, "", token_start_line_, token_start_col_};
    }
}

} // namespace kappa::dsl