#pragma once

#include <memory>
#include <string>
#include <optional>
#include <vector>

#include <mw/database.hpp>
#include <mw/error.hpp>
#include <mw/utils.hpp>

struct LinkItem
{
    enum Visibility {PUBLIC, PRIVATE};
    static std::string visibilityToStr(Visibility v);

    int64_t id;
    int64_t owner_id;
    // Top-level items don’t have parents.
    std::optional<int64_t> parent_id;
    std::string name;
    // If this is empty, it’s a parent.
    std::string url;
    std::string description;
    Visibility visibility;
    mw::Time time;
};

struct User
{
    int64_t id;
    std::string openid_uid;
    std::string name;
};

class DataSourceInterface
{
public:
    virtual ~DataSourceInterface() = default;

    // The schema version is the version of the database. It starts
    // from 1. Every time the schema change, someone should increase
    // this number by 1, manually, by hand. The intended use is to
    // help with database migration.
    virtual mw::E<int64_t> getSchemaVersion() const = 0;

    virtual mw::E<std::optional<User>>
    userByOpenIDUID(const std::string& uid) const = 0;
    virtual mw::E<int64_t> addUser(User&& u) const = 0;
    virtual mw::E<std::optional<User>> userByID(const int64_t) const = 0;
    virtual mw::E<std::optional<User>> userByName(const std::string& name) const = 0;
    virtual mw::E<std::optional<LinkItem>> itemByID(int64_t id) const = 0;
    // Get all children of “parent”.
    virtual mw::E<std::vector<LinkItem>> itemsByParent(int64_t parent) const = 0;
    // Get all top-level items owned by “username”.
    virtual mw::E<std::vector<LinkItem>>
    itemsTopLevelByUser(int64_t user_id) const = 0;
    virtual mw::E<int64_t> addLink(LinkItem&& link) const = 0;

protected:
    virtual mw::E<void> setSchemaVersion(int64_t v) const = 0;
};

class DataSourceSQLite : public DataSourceInterface
{
public:
    explicit DataSourceSQLite(std::unique_ptr<mw::SQLite> conn)
            : db(std::move(conn)) {}
    ~DataSourceSQLite() override = default;

    static mw::E<std::unique_ptr<DataSourceSQLite>>
    fromFile(const std::string& db_file);
    static mw::E<std::unique_ptr<DataSourceSQLite>> newFromMemory();

    mw::E<int64_t> getSchemaVersion() const override;

    mw::E<std::optional<User>>
    userByOpenIDUID(const std::string& uid) const override;
    mw::E<int64_t> addUser(User&& u) const override;
    mw::E<std::optional<User>> userByID(const int64_t) const override;
    mw::E<std::optional<User>> userByName(const std::string& name) const override;
    mw::E<std::optional<LinkItem>> itemByID(int64_t id) const override;
    mw::E<std::vector<LinkItem>> itemsByParent(int64_t parent) const override;
    mw::E<std::vector<LinkItem>> itemsTopLevelByUser(int64_t user_id) const override;

    mw::E<int64_t> addLink(LinkItem&& link) const override;

    // Do not use.
    DataSourceSQLite() = default;

protected:
    mw::E<void> setSchemaVersion(int64_t v) const override;

private:
    std::unique_ptr<mw::SQLite> db;
};