recoll/src/query/dynconf.h

/* Copyright (C) 2004-2017 J.F.Dockes
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the
 *   Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#ifndef _DYNCONF_H_INCLUDED_
#define _DYNCONF_H_INCLUDED_

/**
 * Dynamic configuration storage
 *
 * This used to be called "history" because of the initial usage.
 * Used to store some parameters which would fit neither in recoll.conf,
 * basically because they change a lot, nor in the QT preferences file, mostly 
 * because they are specific to a configuration directory.
 * Examples:
 *  - History of documents selected for preview
 *  - Active and inactive external databases (depend on the 
 *    configuration directory)
 *  - ...
 *
 * The storage is performed in a ConfSimple file, with subkeys and
 * encodings which depend on the data stored. Under each section, the keys 
 * are sequential numeric, so this basically manages a set of lists.
 *
 * The code ensures that a a given value (as defined by the
 * DynConfEntry::equal() method) is only stored once. If this is
 * undesirable, equal() should always return false.
 */

#include <string>
#include <list>
#include <vector>

#include "conftree.h"
#include "base64.h"

/** Interface for a stored object. */
class DynConfEntry {
public:
    virtual ~DynConfEntry() {}
    /** Decode object-as-string coming out from storage */
    virtual bool decode(const std::string &value) = 0;
    /** Encode object state into state for storing */
    virtual bool encode(std::string& value) = 0;
    /** Compare objects */
    virtual bool equal(const DynConfEntry &other) = 0;
};

/** Stored object specialization for generic string storage */
class RclSListEntry : public DynConfEntry {
public:
    RclSListEntry() {}
    virtual ~RclSListEntry() {}
    RclSListEntry(const std::string& v) 
        : value(v) {
    }
    virtual bool decode(const std::string &enc) override {
        base64_decode(enc, value);
        return true;
    }
    virtual bool encode(std::string& enc) override {
        base64_encode(value, enc);
        return true;
    }
    virtual bool equal(const DynConfEntry& other) override {
        const RclSListEntry& e = dynamic_cast<const RclSListEntry&>(other);
        return e.value == value;
    }

    std::string value;
};

/** The dynamic configuration class */
class RclDynConf {
public:
    RclDynConf(const std::string &fn);

    bool ro() {
        return m_data.getStatus() == ConfSimple::STATUS_RO;
    }
    bool rw() {
        return m_data.getStatus() == ConfSimple::STATUS_RW;
    }
    bool ok() {
        return m_data.getStatus() != ConfSimple::STATUS_ERROR;
    }
    std::string getFilename() {
        return m_data.getFilename();
    }

    // Generic methods
    bool eraseAll(const std::string& sk);

    /** Insert new entry for section sk
     * @param sk section this is for
     * @param n  new entry
     * @param s a scratch entry used for decoding and comparisons,
     *        avoiding templating the routine for the actual entry type.
     */
    bool insertNew(const std::string& sk, DynConfEntry &n, DynConfEntry &s, 
                   int maxlen = -1);

    // General method to extract entries. Maybe there would be a way to
    // express the fact that Type should derive from DynConfEntry, not
    // too sure how. We are just certain (further down) that it does
    // have a decode() method. It's up to the user that they call
    // insertNew() and getEntries() for the same type...
    template <template <class, class> class Container, class Type>
    Container<Type, std::allocator<Type>> getEntries(const std::string& sk);

    // Specialized methods for simple strings
    bool enterString(const std::string sk, const std::string value,
                     int maxlen = -1);
    template <template <class, class> class Container>
    Container<std::string, std::allocator<std::string>>
    getStringEntries(const std::string& sk);
    
private:
    ConfSimple   m_data;
};

template <template <class, class> class Container, class Type>
Container<Type, std::allocator<Type>>
RclDynConf::getEntries(const std::string& sk)
{
    Container<Type, std::allocator<Type>> out;
    Type entry;
    std::vector<std::string> names = m_data.getNames(sk);
    for (const auto& name : names) {
        std::string value;
        if (m_data.get(name, value, sk)) {
            if (!entry.decode(value))
                continue;
            out.push_back(entry);
        }
    }
    return out;
}

template <template <class, class> class Container>
Container<std::string, std::allocator<std::string>>
RclDynConf::getStringEntries(const std::string& sk) 
{
    std::vector<RclSListEntry> el = getEntries<std::vector, RclSListEntry>(sk);
    Container<std::string, std::allocator<std::string>> sl;
    for (const auto& entry : el) {
        sl.push_back(entry.value);
    }
    return sl;
}

// Defined subkeys. Values in dynconf.cpp
// History
extern const std::string docHistSubKey;
// All external indexes
extern const std::string allEdbsSk;
// Active external indexes
extern const std::string actEdbsSk;
// Advanced search history
extern const std::string advSearchHistSk;

#endif /* _DYNCONF_H_INCLUDED_ */