/*
Copyright (c) 2016 Microsoft Corporation. All rights reserved.
Released under Apache 2.0 license as described in the file LICENSE.

Author: Gabriel Ebner
*/
#pragma once
#include <string>
#include <utility>
#include <vector>
#include <unordered_map>
#include "util/name.h"
#include "kernel/environment.h"
#include "util/task_queue.h"
#include "library/message_buffer.h"
#include "library/io_state.h"
#include "library/trace.h"
#include "frontends/lean/parser.h"

namespace lean {

enum class module_src {
    OLEAN,
    LEAN,
};

struct unit {};

struct module_info {
    bool m_out_of_date = false;

    module_id m_mod;
    module_src m_source = module_src::LEAN;
    time_t m_mtime = -1, m_trans_mtime = -1;

    struct dependency {
        module_id m_id;
        module_name m_import_name;
        std::shared_ptr<module_info const> m_mod_info;
    };
    std::vector<dependency> m_deps;

    optional<std::string> m_lean_contents;

    period m_version = 0;

    struct parse_result {
        options               m_opts;

        task_result<bool> m_parsed_ok;
        task_result<bool> m_proofs_are_correct;
        bool is_ok() const;

        std::shared_ptr<loaded_module const> m_loaded_module;

        snapshot_vector m_snapshots;
    };

    task_result<parse_result> m_result;
    snapshot_vector m_still_valid_snapshots;

    task_result<unit> m_olean_task;

    environment const & get_produced_env() const {
        return m_result.get().m_loaded_module->m_env.get();
    }
};

class module_vfs {
public:
    virtual ~module_vfs() {}
    // need to support changed lean dependencies of olean files
    // need to support changed editor dependencies of olean files
    virtual std::tuple<std::string, module_src, time_t> load_module(module_id const &, bool can_use_olean) = 0;
};

class fs_module_vfs : public module_vfs {
public:
    std::unordered_set<module_id> m_modules_to_load_from_source;
    std::tuple<std::string, module_src, time_t> load_module(module_id const & id, bool can_use_olean) override;
};

class module_mgr {
    period m_current_period = 1;

    bool m_use_snapshots = false;
    bool m_save_olean = false;

    environment m_initial_env;
    io_state m_ios;
    module_vfs * m_vfs;
    message_buffer * m_msg_buf;

    mutex m_mutex;
    std::unordered_map<module_id, std::shared_ptr<module_info>> m_modules;

    void mark_out_of_date(module_id const & id, buffer<module_id> & to_rebuild);
    void build_module(module_id const & id, bool can_use_olean, name_set module_stack);
    std::vector<module_name> get_direct_imports(module_id const & id, std::string const & contents);
    bool get_snapshots_or_unchanged_module(
            module_id const & id, std::string const & contents, time_t mtime, snapshot_vector &vector);

public:
    module_mgr(module_vfs * vfs, message_buffer * msg_buf, environment const & initial_env, io_state const & ios) :
            m_initial_env(initial_env), m_ios(ios), m_vfs(vfs), m_msg_buf(msg_buf) {}

    void invalidate(module_id const & id);

    std::shared_ptr<module_info const> get_module(module_id const &);

    snapshot_vector get_snapshots(module_id const & id);

    void set_use_snapshots(bool use_snapshots) { m_use_snapshots = use_snapshots; }
    bool get_use_snapshots() const { return m_use_snapshots; }

    void set_save_olean(bool save_olean) { m_save_olean = save_olean; }
    bool get_save_olean() const { return m_save_olean; }

    environment get_initial_env() const { return m_initial_env; }
    options get_options() const { return m_ios.get_options(); }
    io_state get_io_state() const { return m_ios; }
};

environment get_combined_environment(environment const & env0,
                                     buffer<std::shared_ptr<module_info const>> const & mods);

}