#include <regex>
#include <iostream>
#include <map>

#include "show.h"
#include "file.h"
#include "error.h"
#include "state.h"
#include "log.h"
#include "util.h"

int State::class_id = 0;

namespace {

// A sys.path entry reaches only the directory's own files, so the decision
// must not recurse; and the answer is fixed for the run (the search-dir set
// only grows, and a directory's answer does not change), so it is decided
// once per directory per process. The former recursive walk here ran on
// every @eval and took ~200 ms per eval on a document in a large home
// directory (27 s for one render).
bool directory_has_python_file(const std::string& dir)
{
    static std::map<std::string, bool> cache {};
    auto it = cache.find(dir);
    if (it != cache.end()) {
        return it->second;
    }
    bool found = false;
    std::error_code ec {};
    for (const auto& entry : std::filesystem::directory_iterator(dir, ec)) {
        if (entry.is_regular_file(ec) && entry.path().extension() == ".py") {
            found = true;
            break;
        }
    }
    cache[dir] = found;
    return found;
}

} // namespace

bool Var::defined() const
{
    return !m_name.empty();
}

std::vector<std::string> Frame::names() const
{
    std::vector<std::string> result;
    result.reserve(m_vars.size());
    std::transform(m_vars.begin(), m_vars.end(), std::back_inserter(result),
                   [](const auto& pair) { return pair.first; });
    return result;
}

void Frame::set(const std::string& name, const std::string& value,
                const std::string& delim, const std::string& desc, const Locator& loc,
                const Argtype& argtype)
{
    Var v(name, value, delim, desc, loc, argtype);
    m_vars[name] = v;
}

std::pair<Var, bool> Frame::get(const std::string& name) const
{
    std::pair<Var, bool> result {Var(), false};
    if (m_vars.contains(name)) {
        result = {m_vars.at(name), true};
    }
    return result;
}

// State


void State::open_frame(const std::string& name)
{
    Frame f(name);
    // m_frames.push_back(f);
    m_frames.emplace(m_frames.begin(), f);
}


void State::close_frame()
{
    if (m_frames.empty()) {
        throw Internal_error("No frame to close", Locator());
    }
    // Preserve altered machine state:
    string_map machine_state {};
    for (const auto& [name, var] : m_frames[0].m_vars) {
        if (contains(name, "K_")) {
            machine_state[name] = var.m_value;
        }
    }
    m_frames.erase(m_frames.begin());
    for (const auto& [name, value] : machine_state) {
        set(name, value, true);
    }
}

void State::set(const std::string& name, const std::string& value, bool update,
                const std::string& delim, const std::string& desc, const Locator& loc,
                const Argtype& argtype)
{
    if (m_frames.empty()) {
        std::stringstream ss {};
        ss << "No open frame to set " << q_(name) << " to " << q_(value);
        throw Internal_error(ss.str(), Locator());
    }
    auto [current, exists] = m_frames[0].get(name);

    if (exists && current.m_value != klammerstate::no_value && !update) {
        std::stringstream ss {};
        ss << "Variable " << q_(name) << " is already defined at " << current.m_loc.desc()
           << ". Use ':replace <new-value>' to replace the current value of "
           << q_(current.m_value) << ".";
        throw Argument_error(ss.str(), current.m_loc);
    }
    m_frames[0].set(name, value, delim, desc, loc, argtype);
}

void State::set(const std::map<std::string, std::string>& varmap)
{
    for (const auto& [k, v] : varmap) {
        set(k, v);
    }
}

void State::set(const std::map<std::string, std::string>& varmap,
                const Parameter_set& parameters)
{
    for (const auto& [name, value] : varmap) {
        const Parameter* parameter = parameters.find(name);
        set(name, value, false, " ", "", Locator(),
            parameter ? parameter->m_argtype : Argtype());
    }
}


void State::replace(const std::string& name, const std::string& value, bool error_if_not_defined)
{
    if (error_if_not_defined && !get(name).defined()) {
        std::stringstream ss {};
        ss << "Cannot replace value of nonexistent variable " << q_(name) << " with " << q_(value);
        throw Argument_error(ss.str(), Locator());
    }
    set(name, value, true);
}

void State::add_environment_frame()
{
    open_frame(klammerstate::shell_environment_name);
    for (const auto& [name, value] : environment_variables()) {
        set(name, value);
    }
}

Var State::get(const std::string& name, bool error_if_not_defined, const Locator& loc) const
{
    for (const auto& f : m_frames) {
        auto [result, found] = f.get(name);
        if (found) {
            return result;
        }
    }
    if (error_if_not_defined) {
        // Which frames were searched belongs IN the error, not printed beside
        // it.  This was a msg() dumping the whole state to stdout before the
        // throw -- scaffolding, on the wrong stream, and separated from the
        // message it was explaining.  The frame NAMES are the useful part: a
        // variable missing because the expected frame was never opened looks
        // exactly like one that was never set.
        strings_t frame_names {};
        for (const auto& f : m_frames) {
            frame_names.push_back(f.m_name);
        }
        throw Argument_error(
            "Variable " + q_(name) + " not defined (searched: "
            + join(frame_names, ", ") + ")", loc);
    } else {
        return Var();
    }
}

std::string State::value(const std::string& name, bool error_if_not_defined, const Locator& loc) const
{
    return get(name, error_if_not_defined, loc).m_value;
}

std::string State::subst(const std::string& text, bool quote_values) const
{
    (void)K::log(3);
    std::string result = text;
    std::regex varpat(R"(\*(\w+)\*)");
    for (std::sregex_iterator iter(text.begin(), text.end(), varpat), end; iter != end; ++iter) {
        std::string match = iter->str();
        std::string var = (*iter)[1].str();
        //std::cout << "Found: " << iter->str() << sp_arrow << (*iter)[1].str() << "\n";
        // std::cout << "Found: " << match << sp_arrow << var << "\n";

        //std::string value = get(var).m_value;

        auto var_value = value(var, false);
        auto printable = q_(var_value);
        if (var_value != klammerstate::no_value) {
            if (quote_values) {
                var_value = q_(var_value);
            }
            result = string_replace(result, match, var_value);
        } else {
            // throw Argument_error("Variable " + printable + " is not defined");
        }
    }
    return result;
}

void State::subst(katom_iter begin, katom_iter end)
{
    (void)K::log(3);
    std::regex varpat(R"((.*?)\*(\w+)\*(.*))");
    for (auto ki = begin; ki < end ; ki++) {
        // msg() << kall << ktype << *ki << "\n";
        std::smatch match;
        if (std::regex_match(ki->m_text, match, varpat)
            && ki->m_type == katom_t::karg) {
            //auto [var, found] = get(match[1]);
            auto var_value = value(match[2], true, begin->m_loc);
            if (var_value != klammerstate::no_value) {
                (void)K::log(3, "Found subst:", match[1].str(), var_value);
                std::stringstream ss {};
                ss << match[1] << var_value << match[3];
                ki->m_text = ss.str(); // match[1] + var_value + match[3];
            } else {
                throw Argument_error("Variable " + q_(match[1]) + " is not defined", begin->m_loc);
            }
            
        }
    }
}

void prohibit_change_of_description(
    const std::string& name, bool defined, const std::string& old_desc,
    const std::string& new_desc, const Locator& old_loc, const Locator& loc)
{
    if (defined && !old_desc.empty() && !new_desc.empty()) {
        std::stringstream ss {};
        ss << "The " << q_(name) << " variable's description is already defined";
        if (new_desc != old_desc) {
            ss << "; the description cannot be changed to " << q_(new_desc)
               << " from " << q_(old_desc); 
        }
        ss << " at " << old_loc.desc() << ".";

        throw Argument_error(ss.str(), loc);
    }
}


// Parameter_set m_parameters = Parameter_set("name :value :append :replace :delim :desc");

void State::parse_state_katoms(katom_iter begin, katom_iter end, katom_list& katoms)
{
    (void)K::log(3, *begin, *(end-1));
    // std::cout << "parse_katoms: " << std::pair(begin + 1, end - 1) << "\n";
    auto [positional, optional, rest] = argument_split(begin + 1, end - 1);
    auto args = m_parameters.value_map(positional, optional, rest, begin->m_loc);

    // std::cout << std::setfill(' ') << "\nArgument values:\n" << args;

    Var current = get(args["name"]);
    bool defined = current.defined();
    std::string delim = args["delim"];
    delim = delim.empty() ? " " : delim;

    prohibit_change_of_description(
        args["name"], defined, current.m_desc, args["desc"], current.m_loc, begin->m_loc);

    if (defined && !args["replace"].empty()) {
        replace(args["name"], args["replace"]);
    } else if (defined && !args["append"].empty()) {
        replace(args["name"], current.m_value + delim + args["append"]);
    } else if (!args["value"].empty()) {
        set(args["name"], args["value"], false, delim, args["desc"], begin->m_loc);
    }

    modify_type(katom_t::replaced, begin, end);
    auto next_iter = end;
    ignore_whitespace(next_iter, katoms);
}

std::vector<std::string> State::all_names() const
{
    std::vector<std::string> result {};
    for (const Frame& f : m_frames) {
        for (const auto& [name, var] : f.m_vars) {
            // std::cout << "Name: " << name << "\n";
            result.push_back(name);
        }
    }
    return result;
}


void State::add_search_dir(const std::string& dir)
{
    if (!dir.empty()
        && std::find(m_search_dirs.begin(), m_search_dirs.end(), dir)
           == m_search_dirs.end()) {
        m_search_dirs.push_back(dir);
    }
}


std::string State::python_code()
{
    (void)K::log(3);
    std::vector<std::string> names = all_names();
    std::string margin = "    ";
    std::stringstream ss {};

    ss << "import sys\n";
    strings_t python_dirs = sks_dirs();
    // The directories of the files this Machine has read: a module next to
    // the file whose @eval names it is found regardless of the cwd.
    python_dirs.insert(python_dirs.end(),
                       m_search_dirs.begin(), m_search_dirs.end());
    for (const auto& d : python_dirs) {
        if (directory_has_python_file(d)) {
            ss << "sys.path.append('" << d << "')\n";
        }
    }
    if (!m_frames.empty()) {
        int name_length = max_length(names);
        ss << "class K:\n"
           << margin << std::left << std::setw(name_length) << "K_eval_id" << " = "
           << State::class_id++ << "\n";
        for (const auto& name : names) {
            Var var = get(name);
            ss << var.m_argtype.python_value(name, {var.m_value}, name_length) << "\n";
        }
    }
    // msg() << ss.str() << "\n";
    return ss.str();
}


std::string State::describe(bool show_environment, int margin_size) const
{
    std::string margin(margin_size, ' ');
    int i = m_frames.size() - 1;
    std::stringstream ss {};
    for (const auto& f : m_frames) {
        int width = max_key_length(f.m_vars);
        ss << margin << "Frame " << i-- << ": " << f.m_name << "\n";
        if ((f.m_name != klammerstate::shell_environment_name) ||
            (show_environment && f.m_name == klammerstate::shell_environment_name)) {
            for (const auto& [key, value] : f.m_vars) {
                std::string print_value = value.m_value;
                if (print_value == klammerstate::no_value) {
                    print_value = "<no-value>";
                }
                ss << margin << "  " << std::setw(width) << std::left << key << "  "
                   << abbrev(print_value) << "\n";
            }
        }
    }
    ss << "\n";
    return ss.str();
}