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

#include <filesystem>
#include <format>
#include <fstream>
#include <sstream>
#include <stdexcept>

namespace kappa::dsl {

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

    SystemConfig parse();

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

    bool parse_bool();
    void parse_system_block(SystemConfig& cfg);
    void parse_packages_block(SystemConfig& cfg);
    void parse_services_block(SystemConfig& cfg);
    void parse_boot_block(SystemConfig& cfg);
    void parse_users_block(SystemConfig& cfg);

    std::string consume_ident();
    std::string consume_string();

    Token current_;
    Lexer lexer_;
};

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

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

Token SysParser::consume(TokenType type) {
    if (!at(type)) {
        if (type == TokenType::Rbrace && at(TokenType::Eof)) {
            throw ParseError(current_.line, current_.col,
                           msg_unclosed_block("block"));
        }
        if (type == TokenType::String && at(TokenType::Ident)) {
            throw ParseError(current_.line, current_.col, msg_not_a_string());
        }
        throw ParseError(current_.line, current_.col,
                        msg_expected(token_name(type), token_name(current_.type)));
    }
    Token t = std::move(current_);
    advance();
    return t;
}

std::string SysParser::consume_ident() {
    if (at(TokenType::Ident) ||
        at(TokenType::KwEnv) ||
        at(TokenType::KwService) ||
        at(TokenType::KwAssert) ||
        at(TokenType::KwImport) ||
        at(TokenType::KwSha256) ||
        at(TokenType::KwSha512) ||
        at(TokenType::KwMd5) ||
        at(TokenType::KwConfig) ||
        at(TokenType::KwFeatures) ||
        at(TokenType::KwVersion) ||
        at(TokenType::KwSource) ||
        at(TokenType::KwLicense) ||
        at(TokenType::KwPatches) ||
        at(TokenType::KwConst) ||
        at(TokenType::KwPackage) ||
        at(TokenType::KwDepends) ||
        at(TokenType::KwProvides) ||
        at(TokenType::KwOutputs) ||
        at(TokenType::KwPrepare) ||
        at(TokenType::KwBuild) ||
        at(TokenType::KwCheck) ||
        at(TokenType::KwInstall) ||
        at(TokenType::KwTrue) ||
        at(TokenType::KwFalse)) {
        auto lexeme = current_.lexeme;
        advance();
        return lexeme;
    }
    throw ParseError(current_.line, current_.col,
                    std::format("expected identifier, got '{}'",
                                token_name(current_.type)));
}

std::string SysParser::consume_string() {
    if (at(TokenType::KwTrue))  { advance(); return "true"; }
    if (at(TokenType::KwFalse)) { advance(); return "false"; }
    if (at(TokenType::Ident))   { auto v = current_.lexeme; advance(); return v; }
    return consume(TokenType::String).lexeme;
}

bool SysParser::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)));
}

SystemConfig SysParser::parse() {
    skip_newlines();
    SystemConfig cfg;

    while (!at(TokenType::Eof)) {
        skip_newlines();
        if (at(TokenType::Eof)) { break; }

        auto kw = consume_ident();

        if (kw == "imports") {
            consume(TokenType::Equals);
            consume(TokenType::Lbracket);
            skip_newlines();
            while (!at(TokenType::Rbracket) && !at(TokenType::Eof)) {
                cfg.imports.push_back(consume(TokenType::String).lexeme);
                skip_newlines();
                if (at(TokenType::Comma)) { consume(TokenType::Comma); }
                skip_newlines();
            }
            consume(TokenType::Rbracket);
        } else if (kw == "assert") {
            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 if (at(TokenType::Ident) && current_.lexeme == "!") {
                    advance();
                    consume(TokenType::Equals);
                    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();
                }
                cfg.assertions.push_back(std::move(a));
                skip_newlines();
            }
            consume(TokenType::Rbrace);
        } else if (kw == "system")   { parse_system_block(cfg); }
        else if (kw == "packages") { parse_packages_block(cfg); }
        else if (kw == "services") { parse_services_block(cfg); }
        else if (kw == "boot")     { parse_boot_block(cfg); }
        else if (kw == "users")    { parse_users_block(cfg); }
        else {
            throw ParseError(current_.line, current_.col,
                           std::format("unknown section '{}'", kw));
        }
    }

    return cfg;
}

void SysParser::parse_system_block(SystemConfig& cfg) {
    consume(TokenType::Lbrace);
    skip_newlines();

    while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
        skip_newlines();
        if (at(TokenType::Rbrace)) { break; }

        auto key = consume_ident();
        if (key == "hostname") {
            consume(TokenType::Equals);
            cfg.system.hostname = consume_string();
        } else if (key == "timezone") {
            consume(TokenType::Equals);
            cfg.system.timezone = consume_string();
        } else if (key == "env") {
            consume(TokenType::Lbrace);
            skip_newlines();
            while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                if (at(TokenType::Newline)) { advance(); continue; }
                auto k = consume_ident();
                bool soft = false;
                if (at(TokenType::Ident) && current_.lexeme == "?") {
                    advance();
                    consume(TokenType::Equals);
                    soft = true;
                } else {
                    consume(TokenType::Equals);
                }
                cfg.system.env.push_back({std::move(k), consume_string(), soft});
                skip_newlines();
            }
            consume(TokenType::Rbrace);
        } else if (key == "config") {
            consume(TokenType::Lbrace);
            skip_newlines();
            while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                if (at(TokenType::Newline)) { advance(); continue; }
                auto k = consume_ident();
                consume(TokenType::Equals);
                cfg.system.config[k] = consume_string();
                skip_newlines();
            }
            consume(TokenType::Rbrace);
        } else if (key == "features") {
            consume(TokenType::Lbrace);
            skip_newlines();
            while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                if (at(TokenType::Newline)) { advance(); continue; }
                auto k = consume_ident();
                consume(TokenType::Equals);
                cfg.system.features[k] = FeatureDef{parse_bool(), false, ""};
                skip_newlines();
            }
            consume(TokenType::Rbrace);
        } else if (key == "rollback") {
            consume(TokenType::Lbrace);
            skip_newlines();
            while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                if (at(TokenType::Newline)) { advance(); continue; }
                auto k = consume_ident();
                consume(TokenType::Equals);
                if (k == "keep") {
                    cfg.system.rollback.keep = parse_int(current_.line, current_.col,
                                                        current_.lexeme);
                    advance();
                }
                skip_newlines();
            }
            consume(TokenType::Rbrace);
        } else {
            throw ParseError(current_.line, current_.col,
                           std::format("unknown system key '{}'", key));
        }
    }
    consume(TokenType::Rbrace);
}

void SysParser::parse_packages_block(SystemConfig& cfg) {
    consume(TokenType::Lbrace);
    skip_newlines();

    while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
        skip_newlines();
        if (at(TokenType::Rbrace)) { break; }

        PackageRef pkg;
        pkg.name = consume_ident();

        if (at(TokenType::Lbrace)) {
            consume(TokenType::Lbrace);
            skip_newlines();
            while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                skip_newlines();
                if (at(TokenType::Rbrace)) { break; }
                auto key = consume_ident();
                if (key == "version") {
                    consume(TokenType::Equals);
                    pkg.version = consume_string();
                } else if (key == "features") {
                    consume(TokenType::Lbrace);
                    skip_newlines();
                    while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                        if (at(TokenType::Newline)) { advance(); continue; }
                        auto k = consume_ident();
                        consume(TokenType::Equals);
                        pkg.features[k] = FeatureDef{parse_bool(), false, ""};
                        skip_newlines();
                    }
                    consume(TokenType::Rbrace);
                } else if (key == "config") {
                    consume(TokenType::Lbrace);
                    skip_newlines();
                    while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                        if (at(TokenType::Newline)) { advance(); continue; }
                        auto k = consume_ident();
                        consume(TokenType::Equals);
                        pkg.config[k] = current_.lexeme;
                        advance();
                        skip_newlines();
                    }
                    consume(TokenType::Rbrace);
                }
            }
            consume(TokenType::Rbrace);
        }
        cfg.packages.push_back(std::move(pkg));
    }
    consume(TokenType::Rbrace);
}

void SysParser::parse_services_block(SystemConfig& cfg) {
    consume(TokenType::Lbrace);
    skip_newlines();

    while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
        skip_newlines();
        if (at(TokenType::Rbrace)) { break; }

        ServiceRef svc;
        svc.name = consume_ident();

        if (at(TokenType::Lbrace)) {
            consume(TokenType::Lbrace);
            skip_newlines();
            while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                if (at(TokenType::Newline)) { advance(); continue; }
                auto key = consume_ident();
                if (key == "enable") {
                    consume(TokenType::Equals);
                    svc.enable = parse_bool();
                } else {
                    consume(TokenType::Equals);
                    svc.config[key] = current_.lexeme;
                    advance();
                }
                skip_newlines();
            }
            consume(TokenType::Rbrace);
        }
        cfg.services.push_back(std::move(svc));
    }
    consume(TokenType::Rbrace);
}

void SysParser::parse_boot_block(SystemConfig& cfg) {
    consume(TokenType::Lbrace);
    skip_newlines();

    while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
        skip_newlines();
        if (at(TokenType::Rbrace)) { break; }
        auto key = consume_ident();
        consume(TokenType::Equals);
        auto val = consume_string();
        if (key == "kernel") { cfg.boot.kernel = std::move(val); }
        else if (key == "init")      { cfg.boot.init = std::move(val); }
        else if (key == "efi")       { cfg.boot.efi = std::move(val); }
        else if (key == "swap")      { cfg.boot.swap = std::move(val); }
        else if (key == "root")      { cfg.boot.root = std::move(val); }
        else if (key == "bootloader"){ cfg.boot.bootloader = std::move(val); }
        else { cfg.boot.params[key] = std::move(val); }
        skip_newlines();
    }
    consume(TokenType::Rbrace);
}

void SysParser::parse_users_block(SystemConfig& cfg) {
    consume(TokenType::Lbrace);
    skip_newlines();

    while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
        skip_newlines();
        if (at(TokenType::Rbrace)) { break; }

        UserRef u;
        u.name = consume_ident();

        if (at(TokenType::Lbrace)) {
            consume(TokenType::Lbrace);
            skip_newlines();
            while (!at(TokenType::Rbrace) && !at(TokenType::Eof)) {
                if (at(TokenType::Newline)) { advance(); continue; }
                auto key = consume_ident();
                if (key == "shell") {
                    consume(TokenType::Equals);
                    u.shell = consume_string();
                } else if (key == "groups") {
                    consume(TokenType::Equals);
                    consume(TokenType::Lbracket);
                    skip_newlines();
                    while (!at(TokenType::Rbracket) && !at(TokenType::Eof)) {
                        u.groups.push_back(consume_string());
                        skip_newlines();
                        if (at(TokenType::Comma)) { consume(TokenType::Comma); }
                        skip_newlines();
                    }
                    consume(TokenType::Rbracket);
                } else {
                    consume(TokenType::Equals);
                    u.extra[key] = consume_string();
                }
                skip_newlines();
            }
            consume(TokenType::Rbrace);
        }
        cfg.users.push_back(std::move(u));
    }
    consume(TokenType::Rbrace);
}

SystemConfig parse_system_config(std::string_view source) {
    SysParser p(source);
    return p.parse();
}

static void merge_config(SystemConfig& base, SystemConfig&& imported) {
    if (!imported.system.hostname.empty()) { base.system.hostname = std::move(imported.system.hostname); }
    if (!imported.system.timezone.empty()) { base.system.timezone = std::move(imported.system.timezone); }
    for (auto& e : imported.system.env) { base.system.env.push_back(std::move(e)); }
    for (auto& [k, v] : imported.system.config) { base.system.config[k] = std::move(v); }
    for (auto& [k, v] : imported.system.features) { base.system.features[k] = std::move(v); }
    if (imported.system.rollback.keep > 0) { base.system.rollback.keep = imported.system.rollback.keep; }
    for (auto& p : imported.packages) { base.packages.push_back(std::move(p)); }
    for (auto& s : imported.services) { base.services.push_back(std::move(s)); }
    for (auto& u : imported.users) { base.users.push_back(std::move(u)); }
    if (!imported.boot.kernel.empty())     { base.boot.kernel = std::move(imported.boot.kernel); }
    if (!imported.boot.init.empty())       { base.boot.init = std::move(imported.boot.init); }
    if (!imported.boot.efi.empty())        { base.boot.efi = std::move(imported.boot.efi); }
    if (!imported.boot.swap.empty())       { base.boot.swap = std::move(imported.boot.swap); }
    if (!imported.boot.root.empty())       { base.boot.root = std::move(imported.boot.root); }
    if (!imported.boot.bootloader.empty()) { base.boot.bootloader = std::move(imported.boot.bootloader); }
    for (auto& [k, v] : imported.boot.params) { base.boot.params[k] = std::move(v); }
}

SystemConfig resolve_imports(const SystemConfig& cfg, const std::string& base_dir) {
    auto resolved = cfg;
    for (auto& import_path : cfg.imports) {
        auto full_path = std::filesystem::path(base_dir) / import_path;
        std::ifstream in(full_path);
        if (!in) { continue; }
        std::ostringstream buf;
        buf << in.rdbuf();
        auto imported = parse_system_config(buf.str());
        merge_config(resolved, resolve_imports(imported, base_dir));
    }
    resolved.imports.clear();
    return resolved;
}

} // namespace kappa::dsl