/* Copyright (C) 2004 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.,
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */
#ifndef _DB_H_INCLUDED_
#define _DB_H_INCLUDED_

#include "autoconfig.h"

#include <string>
#include <vector>

#include "cstr.h"
#include "refcntr.h"
#include "rcldoc.h"
#include "stoplist.h"
#include "rclconfig.h"
#include "utf8iter.h"
#include "textsplit.h"

using std::string;
using std::vector;

// rcldb defines an interface for a 'real' text database. The current 
// implementation uses xapian only, and xapian-related code is in rcldb.cpp
// If support was added for other backend, the xapian code would be moved in 
// rclxapian.cpp, another file would be created for the new backend, and the
// configuration/compile/link code would be adjusted to allow choosing. There 
// is no plan for supporting multiple different backends.
// 
// In no case does this try to implement a useful virtualized text-db interface
// The main goal is simplicity and good matching to usage inside the recoll
// user interface. In other words, this is not exhaustive or well-designed or 
// reusable.
//
// Unique Document Identifier: uniquely identifies a document in its
// source storage (file system or other). Used for up to date checks
// etc. "udi". Our user is responsible for making sure it's not too
// big, cause it's stored as a Xapian term (< 150 bytes would be
// reasonable)

class RclConfig;

namespace Rcl {

// Omega compatible values. We leave a hole for future omega values. Not sure 
// it makes any sense to keep any level of omega compat given that the index
// is incompatible anyway.
enum value_slot {
    // Omega-compatible values:
    VALUE_LASTMOD = 0,	// 4 byte big endian value - seconds since 1970.
    VALUE_MD5 = 1,	// 16 byte MD5 checksum of original document.
    VALUE_SIZE = 2,     // sortable_serialise(<file size in bytes>)

    // Recoll only:
    VALUE_SIG = 10      // Doc sig as chosen by app (ex: mtime+size
};

class SearchData;
class TermIter;
class Query;

/** Used for returning result lists for index terms matching some criteria */
class TermMatchEntry {
public:
    TermMatchEntry() 
	: wcf(0) 
    {
    }
    TermMatchEntry(const string& t, int f, int d)
	: term(t), wcf(f), docs(d) 
    {
    }
    TermMatchEntry(const string& t)
    : term(t), wcf(0) 
    {
    }
    bool operator==(const TermMatchEntry &o) const 
    { 
	return term == o.term;
    }
    bool operator<(const TermMatchEntry &o) const 
    { 
	return term < o.term;
    }

    string term;
    int    wcf; // Total count of occurrences within collection.
    int    docs; // Number of documents countaining term.
};

/** Term match result list header: statistics and global info */
class TermMatchResult {
public:
    TermMatchResult() 
    {
	clear();
    }
    void clear() 
    {
	entries.clear(); 
    }
    // Term expansion
    vector<TermMatchEntry> entries;
    // If a field was specified, this is the corresponding index prefix
    string prefix;
};

class DbStats {
public:
    DbStats()
	:dbdoccount(0), dbavgdoclen(0), mindoclen(0), maxdoclen(0)
    {
    }
    // Index-wide stats
    unsigned int dbdoccount;
    double       dbavgdoclen;
    size_t       mindoclen;
    size_t       maxdoclen;
};

inline bool has_prefix(const string& trm)
{
    if (o_index_stripchars) {
	return !trm.empty() && 'A' <= trm[0] && trm[0] <= 'Z';
    } else {
	return !trm.empty() && trm[0] == ':';
    }
}

inline string strip_prefix(const string& trm)
{
    if (trm.empty())
	return trm;
    string::size_type st = 0;
    if (o_index_stripchars) {
	st = trm.find_first_not_of("ABCDEFIJKLMNOPQRSTUVWXYZ");
	if (st == string::npos)
	    return string();
    } else {
	if (has_prefix(trm)) {
	    st = trm.find_last_of(":") + 1;
	} else {
	    return trm;
	}
    }
    return trm.substr(st);
}

inline string wrap_prefix(const string& pfx) 
{
    if (o_index_stripchars) {
	return pfx;
    } else {
	return cstr_colon + pfx + cstr_colon;
    }
}

/**
 * Wrapper class for the native database.
 */
class Db {
 public:
    // A place for things we don't want visible here.
    class Native;
    friend class Native;

    /* General stuff (valid for query or update) ****************************/
    Db(const RclConfig *cfp);
    ~Db();

    enum OpenMode {DbRO, DbUpd, DbTrunc};
    enum OpenError {DbOpenNoError, DbOpenMainDb, DbOpenExtraDb};
    bool open(OpenMode mode, OpenError *error = 0);
    bool close();
    bool isopen();

    /** Get explanation about last error */
    string getReason() const {return m_reason;}

    /** Return all possible stemmer names */
    static vector<string> getStemmerNames();

    /** Return existing stemming databases */
    vector<string> getStemLangs();

    /** Test word for spelling correction candidate: not too long, no 
	special chars... */
    static bool isSpellingCandidate(const string& term)
    {
	if (term.empty() || term.length() > 50)
	    return false;
	if (has_prefix(term))
	    return false;
	Utf8Iter u8i(term);
	if (TextSplit::isCJK(*u8i)) 
	    return false;
	if (term.find_first_of(" !\"#$%&()*+,-./0123456789:;<=>?@[\\]^_`{|}~") 
	    != string::npos)
	    return false;
	return true;
    }


#ifdef TESTING_XAPIAN_SPELL
    /** Return spelling suggestion */
    string getSpellingSuggestion(const string& word);
#endif

    /* The next two, only for searchdata, should be somehow hidden */
    /* Return configured stop words */
    const StopList& getStopList() const {return m_stops;}
    /* Field name to prefix translation (ie: author -> 'A') */
    bool fieldToTraits(const string& fldname, const FieldTraits **ftpp);

    /* Update-related methods ******************************************/

    /** Test if the db entry for the given udi is up to date (by
     * comparing the input and stored sigs). This is used both when 
     * indexing and querying (before opening a document using stale info),
     * **This assumes that the udi pertains to the main index (idxi==0).**
     * Side-effect when the db is writeable: set the existence flag
     * for the file document and all subdocs if any (for later use by
     * 'purge()')
     */
    bool needUpdate(const string &udi, const string& sig, bool *existed=0);

    /** Indicate if we are doing a systematic reindex. This complements
	needUpdate() return */
    bool inFullReset() {return o_inPlaceReset || m_mode == DbTrunc;}

    /** Add or update document identified by unique identifier.
     * @param config Config object to use. Can be the same as the member config
     *   or a clone, to avoid sharing when called in multithread context.
     * @param udi the Unique Document Identifier is opaque to us. 
     *   Maximum size 150 bytes.
     * @param parent_udi the UDI for the container document. In case of complex
     *  embedding, this is not always the immediate parent but the UDI for
     *  the container file (which may be a farther ancestor). It is
     *  used for purging subdocuments when a file ceases to exist and
     *  to set the existence flags of all subdocuments of a container
     *  that is found to be up to date. In other words, the
     *  parent_udi is the UDI for the ancestor of the document which
     *  is subject to needUpdate() and physical existence tests (some
     *  kind of file equivalent). Empty for top-level docs. Should
     *  probably be renamed container_udi.
     * @param doc container for document data. Should have been filled as 
     *   much as possible depending on the document type. 
     */
    bool addOrUpdate(const string &udi, 
		     const string &parent_udi, Doc &doc);
#ifdef IDX_THREADS
    void waitUpdIdle();
#endif

    /** Delete document(s) for given UDI, including subdocs */
    bool purgeFile(const string &udi, bool *existed = 0);
    /** Delete subdocs with an out of date sig. We do this to purge
	obsolete subdocs during a partial update where no general purge
	will be done */
    bool purgeOrphans(const string &udi);

    /** Remove documents that no longer exist in the file system. This
     * depends on the update map, which is built during
     * indexing (needUpdate() / addOrUpdate()). 
     *
     * This should only be called after a full walk of
     * the file system, else the update map will not be complete, and
     * many documents will be deleted that shouldn't, which is why this
     * has to be called externally, rcldb can't know if the indexing
     * pass was complete or partial.
     */
    bool purge();

    /** Create stem expansion database for given languages. */
    bool createStemDbs(const std::vector<std::string> &langs);
    /** Delete stem expansion database for given language. */
    bool deleteStemDb(const string &lang);

    /* Query-related methods ************************************/

    /** Return total docs in db */
    int  docCnt(); 
    /** Return count of docs which have an occurrence of term */
    int termDocCnt(const string& term);
    /** Add extra Xapian database for querying. 
     * @param dir must point to something which can be passed as parameter 
     *      to a Xapian::Database constructor (directory or stub).
     */
    bool addQueryDb(const string &dir);
    /** Remove extra database. if dir == "", remove all. */
    bool rmQueryDb(const string &dir);
    /** Look where the doc result comes from. 
     * @param doc must come from a db query so that "opaque" xdocid is set.
     * @return: 0 main index, (size_t)-1 don't know, 
     *   other: order of database in add_database() sequence.
     */
    size_t whatDbIdx(const Doc& doc);

    /** Tell if directory seems to hold xapian db */
    static bool testDbDir(const string &dir, bool *stripped = 0);

    /** Return the index terms that match the input string
     * Expansion is performed either with either wildcard or regexp processing
     * Stem expansion is performed if lang is not empty 
     * 
     * @param typ_sens defines the kind of expansion: none, wildcard, 
     *    regexp or stemming. "none" will still expand case and
     *    diacritics depending on the casesens and diacsens flags.
     * @param lang sets the stemming language(s). Can be a space-separated list
     * @param term is the term to expand
     * @param result is the main output
     * @param max defines the maximum result count
     * @param field if set, defines the field within with the expansion should
     *        be performed. Only used for wildcards and regexps, stemming is
     *        always global. If this is set, the resulting output terms 
     *        will be appropriately prefixed and the prefix value will be set 
     *        in the TermMatchResult header
     */
    enum MatchType {ET_NONE=0, ET_WILD=1, ET_REGEXP=2, ET_STEM=3, 
		    ET_DIACSENS=8, ET_CASESENS=16};
    int matchTypeTp(int tp) 
    {
	return tp & 7;
    }
    bool termMatch(int typ_sens, const string &lang, const string &term, 
		   TermMatchResult& result, int max = -1, 
		   const string& field = cstr_null);
    bool dbStats(DbStats& stats);
    /** Return min and max years for doc mod times in db */
    bool maxYearSpan(int *minyear, int *maxyear);
    /** Return all mime types in index. This can be different from the
	ones defined in the config because of 'file' command
	usage. Inserts the types at the end of the parameter */
    bool getAllDbMimeTypes(std::vector<std::string>&);

    /** Wildcard expansion specific to file names. Internal/sdata use only */
    bool filenameWildExp(const string& exp, vector<string>& names, int max);

    /** Set parameters for synthetic abstract generation */
    void setAbstractParams(int idxTrunc, int synthLen, int syntCtxLen);
    int getAbsCtxLen() const 
    {
	return m_synthAbsWordCtxLen;
    }
    int getAbsLen() const
    {
	return m_synthAbsLen;
    }
    /** Get document for given udi
     *
     * Used by the 'history' feature, and to retrieve ancestor documents.
     * @param udi The unique document identifier.
     * @param idxdoc A document from the same database as an opaque way to pass
     *   the database id (e.g.: when looking for parent in a multi-database 
     *   context).
     * @param[out] doc The output Recoll document.
     * @return True for success.
     */
    bool getDoc(const string &udi, const Doc& idxdoc, Doc &doc);

    /** Test if documents has sub-documents. 
     *
     * This can always be detected for file-level documents, using the
     * postlist for the parent term constructed with udi.
     *
     * For non file-level documents (e.g.: does an email inside an
     * mbox have attachments ?), detection is dependant on the filter
     * having set an appropriate flag at index time. Higher level code
     * can't detect it because the doc for the parent may have been
     * seen before any children. The flag is stored as a value in the
     * index.
     */
    bool hasSubDocs(const Doc &idoc);

    /** Get subdocuments of given document. 
     *
     * For file-level documents, these are all docs indexed by the
     * parent term built on idoc.udi. For embedded documents, the
     * parent doc is looked for, then its subdocs list is 
     * filtered using the idoc ipath as a prefix.
     */
    bool getSubDocs(const Doc& idoc, vector<Doc>& subdocs);

    /** Get duplicates (md5) of document */
    bool docDups(const Doc& idoc, std::vector<Doc>& odocs);

    /* The following are mainly for the aspell module */
    /** Whole term list walking. */
    TermIter *termWalkOpen();
    bool termWalkNext(TermIter *, string &term);
    void termWalkClose(TermIter *);
    /** Test term existence */
    bool termExists(const string& term);
    /** Test if terms stem to different roots. */
    bool stemDiffers(const string& lang, const string& term, 
		     const string& base);

    const RclConfig *getConf() {return m_config;}

    /** 
	Activate the "in place reset" mode where all documents are
	considered as needing update. This is a global/per-process
	option, and can't be reset. It should be set at the start of
	the indexing pass. 2012-10: no idea why this is done this way...
    */
    static void setInPlaceReset() {o_inPlaceReset = true;}

    /** Flush interval get/set. This is used by the first indexing
	pass to override the config value and flush more rapidly
	initially so that the user can quickly play with queries */
    int getFlushMb() 
    {
	return  m_flushMb;
    }
    void setFlushMb(int mb)
    {
	m_flushMb = mb;
    }
    bool doFlush();

    /* This has to be public for access by embedded Query::Native */
    Native *m_ndb; 
private:
    const RclConfig *m_config;
    string     m_reason; // Error explanation

    // Xapian directories for additional databases to query
    vector<string> m_extraDbs;
    OpenMode m_mode;
    // File existence vector: this is filled during the indexing pass. Any
    // document whose bit is not set at the end is purged
    vector<bool> updated;
    // Text bytes indexed since beginning
    long long    m_curtxtsz;
    // Text bytes at last flush
    long long    m_flushtxtsz;
    // Text bytes at last fsoccup check
    long long    m_occtxtsz;
    // First fs occup check ?
    int         m_occFirstCheck;

    /***************
     * Parameters cached out of the configuration files. Logically const 
     * after init */
    // Stop terms: those don't get indexed.
    StopList m_stops;
    // This is how long an abstract we keep or build from beginning of
    // text when indexing. It only has an influence on the size of the
    // db as we are free to shorten it again when displaying
    int          m_idxAbsTruncLen;
    // This is the size of the abstract that we synthetize out of query
    // term contexts at *query time*
    int          m_synthAbsLen;
    // This is how many words (context size) we keep around query terms
    // when building the abstract
    int          m_synthAbsWordCtxLen;
    // Flush threshold. Megabytes of text indexed before we flush.
    int          m_flushMb;
    // Maximum file system occupation percentage
    int          m_maxFsOccupPc;
    // Database directory
    string       m_basedir;
    // When this is set, all documents are considered as needing a reindex.
    // This implements an alternative to just erasing the index before 
    // beginning, with the advantage that, for small index formats updates, 
    // between releases the index remains available while being recreated.
    static bool o_inPlaceReset;
    /******* End logical constnesss */

#ifdef IDX_THREADS
    friend void *DbUpdWorker(void*);
#endif // IDX_THREADS

    // Internal form of close, can be called during destruction
    bool i_close(bool final);
    // Reinitialize when adding/removing additional dbs
    bool adjustdbs(); 
    bool idxTermMatch(int typ_sens, const string &lang, const string &term, 
		      TermMatchResult& result, int max = -1, 
		      const string& field = cstr_null);

    // Flush when idxflushmb is reached
    bool maybeflush(off_t moretext);
    bool docExists(const string& uniterm);

    /* Copyconst and assignement private and forbidden */
    Db(const Db &) {}
    Db& operator=(const Db &) {return *this;};
};

// This has to go somewhere, and as it needs the Xapian version, this is
// the most reasonable place.
string version_string();

extern const string pathelt_prefix;
extern const string udi_prefix;
extern const string parent_prefix;
extern const string mimetype_prefix;
extern const string unsplitFilenameFieldName;
extern string start_of_field_term;
extern string end_of_field_term;

}

#endif /* _DB_H_INCLUDED_ */
