#include "kappa/dsl/parser.hpp"
#include "kappa/dsl/error.hpp"
#include "kappa/dsl/lexer.hpp"

#include <format>
#include <stdexcept>
#include <string>
#include <vector>

namespace kappa::dsl {

class Parser {
public:
    explicit Parser(std::string_view source) : lexer_(source) { advance(); }

    PackageDef parse();

private:
    void  advance();
    Token consume(TokenType type);
    void  skip_newlines();
    bool  at(TokenType type) const { return current_.type == type; }

    PackageDef parse_package_def();
    void       parse_body(PackageDef& pkg);
    Phase      parse_phase();
    Command    parse_command_line();
    bool       parse_bool();

    std::vector<std::string> parse_string_list();
    Dependency               parse_dependency_item();
    ConfigFile               parse_config_file();
    FeatureDef               parse_feature_def();
    Patch                    parse_patch_item();

    Token current_;
    Lexer lexer_;
};

void Parser::advance() { current_ = lexer_.next(); }

void Parser::skip_newlines() {
    while (at(TokenType::Newline)) { advance(); }
}

Token Parser::consume(TokenType type) {
    if (!at(type)) {
        throw ParseError(current_.line, current_.col,
                        std::format("expected '{}', got '{}'",
                                    token_name(type), token_name(current_.type)));
    }
    Token t = std::move(current_);
    advance();
    return t;
}

PackageDef Parser::parse() {
    skip_newlines();
    return parse_package_def();
}

PackageDef Parser::parse_package_def() {
    consume(TokenType::KwPackage);
    auto name_tok = consume(TokenType::String);
    consume(TokenType::Lbrace);

    PackageDef pkg;
    pkg.name = std::move(name_tok.lexeme);

    parse_body(pkg);

    consume(TokenType::Rbrace);
    return pkg;
}

void Parser::parse_body(PackageDef& pkg) {
    while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
        skip_newlines();
        if (at(TokenType::Rbrace) || at(TokenType::Eof)) { break; }

        switch (current_.type) {
        case TokenType::KwConst: {
            consume(TokenType::KwConst);
            if (at(TokenType::KwVersion)) {
                consume(TokenType::KwVersion);
                consume(TokenType::Equals);
                pkg.version = consume(TokenType::String).lexeme;
                pkg.const_keys.insert("version");
            } else if (at(TokenType::KwSource)) {
                consume(TokenType::KwSource);
                consume(TokenType::Equals);
                pkg.source = consume(TokenType::String).lexeme;
                pkg.const_keys.insert("source");
            } else {
                throw ParseError(current_.line, current_.col,
                                std::format("unexpected token '{}' after const",
                                            token_name(current_.type)));
            }
            break;
        }

        case TokenType::KwVersion:
            consume(TokenType::KwVersion);
            consume(TokenType::Equals);
            pkg.version = consume(TokenType::String).lexeme;
            break;

        case TokenType::KwSource:
            consume(TokenType::KwSource);
            consume(TokenType::Equals);
            pkg.source = consume(TokenType::String).lexeme;
            break;

        case TokenType::KwLicense:
            consume(TokenType::KwLicense);
            consume(TokenType::Equals);
            pkg.license = consume(TokenType::String).lexeme;
            break;

        case TokenType::KwProvides:
            consume(TokenType::KwProvides);
            consume(TokenType::Equals);
            pkg.provides = parse_string_list();
            break;

        case TokenType::KwOutputs:
            consume(TokenType::KwOutputs);
            consume(TokenType::Equals);
            pkg.outputs = parse_string_list();
            break;

        case TokenType::KwDepends:
            consume(TokenType::KwDepends);
            consume(TokenType::Equals);
            consume(TokenType::Lbracket);
            skip_newlines();
            while (!at(TokenType::Rbracket) && !at(TokenType::Eof)) {
                pkg.depends.push_back(parse_dependency_item());
                skip_newlines();
                if (at(TokenType::Comma)) { consume(TokenType::Comma); }
                skip_newlines();
            }
            consume(TokenType::Rbracket);
            break;

        case TokenType::KwFeatures:
            consume(TokenType::KwFeatures);
            consume(TokenType::Lbrace);
            skip_newlines();
            while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                if (at(TokenType::Newline)) { advance(); continue; }
                auto key = consume(TokenType::Ident).lexeme;
                consume(TokenType::Equals);
                pkg.features[key] = parse_feature_def();
                skip_newlines();
            }
            consume(TokenType::Rbrace);
            break;

        case TokenType::KwConfig:
            consume(TokenType::KwConfig);
            consume(TokenType::Lbrace);
            skip_newlines();
            while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                if (at(TokenType::Newline)) { advance(); continue; }
                pkg.config_files.push_back(parse_config_file());
                skip_newlines();
            }
            consume(TokenType::Rbrace);
            break;

        case TokenType::KwPatches:
            consume(TokenType::KwPatches);
            consume(TokenType::Equals);
            consume(TokenType::Lbracket);
            skip_newlines();
            while (!at(TokenType::Rbracket) && !at(TokenType::Eof)) {
                pkg.patches.push_back(parse_patch_item());
                skip_newlines();
                if (at(TokenType::Comma)) { consume(TokenType::Comma); }
                skip_newlines();
            }
            consume(TokenType::Rbracket);
            break;

        case TokenType::KwEnv:
            consume(TokenType::KwEnv);
            consume(TokenType::Lbrace);
            skip_newlines();
            while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                if (at(TokenType::Newline)) { advance(); continue; }
                auto key = consume(TokenType::Ident).lexeme;
                bool soft = false;
                if (at(TokenType::Ident) && current_.lexeme == "?=") {
                    soft = true;
                    advance();
                } else {
                    consume(TokenType::Equals);
                }
                pkg.env_entries.push_back(
                    {std::move(key), consume(TokenType::String).lexeme, soft});
                skip_newlines();
            }
            consume(TokenType::Rbrace);
            break;

        case TokenType::KwService:
            consume(TokenType::KwService);
            consume(TokenType::Lbrace);
            skip_newlines();
            while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                if (at(TokenType::Newline)) { advance(); continue; }
                auto init_name = current_.lexeme;
                advance();
                consume(TokenType::Lbrace);
                skip_newlines();
                ServiceInit si;
                while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                    if (at(TokenType::Newline)) { advance(); continue; }
                    auto key = current_.lexeme;
                    advance();
                    consume(TokenType::Equals);
                    if (key == "exec") {
                        si.exec = consume(TokenType::String).lexeme;
                    } else if (key == "type") {
                        si.type = consume(TokenType::String).lexeme;
                    } else if (key == "user") {
                        si.user = consume(TokenType::String).lexeme;
                    } else if (key == "ports") {
                        consume(TokenType::Lbracket);
                        skip_newlines();
                        while (!at(TokenType::Rbracket) && !at(TokenType::Eof)) {
                            si.ports.push_back(
                                parse_int(current_.line, current_.col,
                                         current_.lexeme));
                            advance();
                            skip_newlines();
                            if (at(TokenType::Comma)) { consume(TokenType::Comma); }
                            skip_newlines();
                        }
                        consume(TokenType::Rbracket);
                    } else {
                        si.env[key] = consume(TokenType::String).lexeme;
                    }
                    skip_newlines();
                }
                consume(TokenType::Rbrace);
                pkg.service[std::string(init_name)] = std::move(si);
                skip_newlines();
            }
            consume(TokenType::Rbrace);
            break;

        case TokenType::KwAssert:
            consume(TokenType::KwAssert);
            consume(TokenType::Lbrace);
            skip_newlines();
            while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                if (at(TokenType::Newline)) { advance(); continue; }
                Assertion a;
                a.message = consume(TokenType::String).lexeme;
                consume(TokenType::Ident); // ":"
                a.field = current_.lexeme;
                advance();
                if (at(TokenType::Equals)) {
                    advance();
                    if (at(TokenType::Equals)) {
                        a.op = "=="; advance();
                    } else {
                        a.op = "=";
                    }
                } else {
                    a.op = current_.lexeme; advance();
                }
                if (at(TokenType::String)) {
                    a.value = consume(TokenType::String).lexeme;
                } else if (at(TokenType::KwTrue)) {
                    a.value = "true"; advance();
                } else if (at(TokenType::KwFalse)) {
                    a.value = "false"; advance();
                } else {
                    a.value = current_.lexeme; advance();
                }
                pkg.assertions.push_back(std::move(a));
                skip_newlines();
            }
            consume(TokenType::Rbrace);
            break;

        case TokenType::KwPrepare:
            consume(TokenType::KwPrepare);
            pkg.prepare = parse_phase();
            break;

        case TokenType::KwBuild:
            consume(TokenType::KwBuild);
            pkg.build = parse_phase();
            break;

        case TokenType::KwCheck:
            consume(TokenType::KwCheck);
            pkg.check = parse_phase();
            break;

        case TokenType::KwInstall:
            consume(TokenType::KwInstall);
            pkg.install = parse_phase();
            break;

        default:
            throw ParseError(current_.line, current_.col,
                           std::format("unexpected token '{}' in package body",
                                       token_name(current_.type)));
        }
    }
}

std::vector<std::string> Parser::parse_string_list() {
    consume(TokenType::Lbracket);
    skip_newlines();
    std::vector<std::string> items;
    while (!at(TokenType::Rbracket) && !at(TokenType::Eof)) {
        items.push_back(consume(TokenType::String).lexeme);
        skip_newlines();
        if (at(TokenType::Comma)) { consume(TokenType::Comma); }
        skip_newlines();
    }
    consume(TokenType::Rbracket);
    return items;
}

Dependency Parser::parse_dependency_item() {
    if (at(TokenType::String)) {
        auto raw = consume(TokenType::String).lexeme;
        auto colon = raw.find(':');
        if (colon != std::string::npos) {
            return {raw.substr(0, colon), "", raw.substr(colon + 1)};
        }
        return {std::move(raw), "", ""};
    }

    consume(TokenType::Lbrace);
    skip_newlines();
    Dependency dep;
    while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
        if (at(TokenType::Newline)) { advance(); continue; }
        auto key = current_.lexeme;  // accept Ident or keyword as object key
        advance();
        consume(TokenType::Equals);
        if (key == "name")    { dep.name    = consume(TokenType::String).lexeme; }
        else if (key == "version") { dep.version = consume(TokenType::String).lexeme; }
        else if (key == "output")  { dep.output  = consume(TokenType::String).lexeme; }
        else if (key == "feature") { dep.feature = consume(TokenType::String).lexeme; }
        else { throw ParseError(current_.line, current_.col,
                                std::format("unknown dependency key '{}'", key)); }
        skip_newlines();
        if (at(TokenType::Comma)) { consume(TokenType::Comma); }
        skip_newlines();
    }
    consume(TokenType::Rbrace);
    return dep;
}

ConfigFile Parser::parse_config_file() {
    consume(TokenType::Ident); // "file"
    ConfigFile cf;
    cf.path = consume(TokenType::String).lexeme;

    if (at(TokenType::Ident) && current_.lexeme == "mode") {
        advance();
        consume(TokenType::Equals);
        cf.mode = consume(TokenType::String).lexeme;
    }

    consume(TokenType::Lbrace);
    skip_newlines();
    while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
        if (at(TokenType::Newline)) { advance(); continue; }
        auto key = current_.lexeme;
        advance();
        consume(TokenType::Equals);
        std::string val;
        while (!at(TokenType::Newline) && !at(TokenType::Rbrace) && !at(TokenType::Eof)) {
            if (!val.empty() && !at(TokenType::Comma)) { val += ' '; }
            val += current_.lexeme;
            advance();
        }
        cf.entries[key] = std::move(val);
        skip_newlines();
    }
    consume(TokenType::Rbrace);
    return cf;
}

bool Parser::parse_bool() {
    if (at(TokenType::KwTrue))  { advance(); return true; }
    if (at(TokenType::KwFalse)) { advance(); return false; }
    throw ParseError(current_.line, current_.col,
                    std::format("expected 'true' or 'false', got '{}'",
                                token_name(current_.type)));
}

FeatureDef Parser::parse_feature_def() {
    if (at(TokenType::KwTrue) || at(TokenType::KwFalse)) {
        return {parse_bool(), false, ""};
    }

    consume(TokenType::Lbrace);
    skip_newlines();
    FeatureDef f;
    while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
        if (at(TokenType::Newline)) { advance(); continue; }
        auto key = current_.lexeme;
        advance();
        consume(TokenType::Equals);
        if (key == "enabled") {
            f.enabled = parse_bool();
        } else if (key == "force") {
            f.force = parse_bool();
        } else if (key == "flag") {
            std::string val;
            while (!at(TokenType::Newline) && !at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                if (!val.empty() && !at(TokenType::Comma)) { val += ' '; }
                val += current_.lexeme;
                advance();
            }
            f.flag = std::move(val);
        }
        skip_newlines();
        if (at(TokenType::Comma)) { consume(TokenType::Comma); }
        skip_newlines();
    }
    consume(TokenType::Rbrace);
    return f;
}

Patch Parser::parse_patch_item() {
    if (at(TokenType::String)) {
        return {consume(TokenType::String).lexeme, "", 1};
    }

    consume(TokenType::Lbrace);
    skip_newlines();
    Patch p;
    while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
        if (at(TokenType::Newline)) { advance(); continue; }
        auto key = current_.lexeme;
        advance();
        consume(TokenType::Equals);
        if (key == "url") {
            p.url = consume(TokenType::String).lexeme;
        } else if (key == "sha256") {
            p.sha256 = consume(TokenType::String).lexeme;
        } else if (key == "level") {
            p.level = parse_int(current_.line, current_.col,
                                current_.lexeme);
            advance();
        }
        skip_newlines();
        if (at(TokenType::Comma)) { consume(TokenType::Comma); }
        skip_newlines();
    }
    consume(TokenType::Rbrace);
    return p;
}

Phase Parser::parse_phase() {
    consume(TokenType::Lbrace);
    skip_newlines();

    Phase phase;
    while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
        if (at(TokenType::Newline)) { advance(); continue; }
        phase.commands.push_back(parse_command_line());
    }
    consume(TokenType::Rbrace);
    return phase;
}

Command Parser::parse_command_line() {
    std::string cmd;
    while (!at(TokenType::Newline) && !at(TokenType::Rbrace) && !at(TokenType::Eof)) {
        if (!cmd.empty() && !at(TokenType::Comma)) { cmd += ' '; }
        cmd += current_.lexeme;
        advance();
    }
    return cmd;
}

PackageDef parse(std::string_view source) {
    Parser p(source);
    return p.parse();
}

} // namespace kappa::dsl