/*
*   $Id: readtags.c 592 2007-07-31 03:30:41Z dhiebert $
*
*   Copyright (c) 1996-2003, Darren Hiebert
*
*   This source code is released into the public domain.
*
*   This module contains functions for reading tag files.
*/

/*
*   INCLUDE FILES
*/
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <stdio.h>
#include <errno.h>
#include <sys/types.h>  /* to declare off_t */

#include "readtags.h"

/*
*   MACROS
*/
#define TAB '\t'


/*
*   DATA DECLARATIONS
*/
typedef struct {
    size_t size;
    char *buffer;
} vstring;

/* Information about current tag file */
struct sTagFile {
        /* has the file been opened and this structure initialized? */
    short initialized;
        /* format of tag file */
    short format;
        /* how is the tag file sorted? */
    sortType sortMethod;
        /* pointer to file structure */
    FILE* fp;
        /* file position of first character of `line' */
    off_t pos;
        /* size of tag file in seekable positions */
    off_t size;
        /* last line read */
    vstring line;
        /* name of tag in last line read */
    vstring name;
        /* defines tag search state */
    struct {
                /* file position of last match for tag */
            off_t pos; 
                /* name of tag last searched for */
            char *name;
                /* length of name for partial matches */
            size_t nameLength;
                /* peforming partial match */
            short partial;
                /* ignoring case */
            short ignorecase;
    } search;
        /* miscellaneous extension fields */
    struct {
                /* number of entries in `list' */
            unsigned short max;
                /* list of key value pairs */
            tagExtensionField *list;
    } fields;
        /* buffers to be freed at close */
    struct {
            /* name of program author */
        char *author;
            /* name of program */
        char *name;
            /* URL of distribution */
        char *url;
            /* program version */
        char *version;
    } program;
};

/*
*   DATA DEFINITIONS
*/
const char *const EmptyString = "";
const char *const PseudoTagPrefix = "!_";

/*
*   FUNCTION DEFINITIONS
*/

/*
 * Compare two strings, ignoring case.
 * Return 0 for match, < 0 for smaller, > 0 for bigger
 * Make sure case is folded to uppercase in comparison (like for 'sort -f')
 * This makes a difference when one of the chars lies between upper and lower
 * ie. one of the chars [ \ ] ^ _ ` for ascii. (The '_' in particular !)
 */
static int struppercmp (const char *s1, const char *s2)
{
    int result;
    do
    {
        result = toupper ((int) *s1) - toupper ((int) *s2);
    } while (result == 0  &&  *s1++ != '\0'  &&  *s2++ != '\0');
    return result;
}

static int strnuppercmp (const char *s1, const char *s2, size_t n)
{
    int result;
    do
    {
        result = toupper ((int) *s1) - toupper ((int) *s2);
    } while (result == 0  &&  --n > 0  &&  *s1++ != '\0'  &&  *s2++ != '\0');
    return result;
}

static int growString (vstring *s)
{
    int result = 0;
    size_t newLength;
    char *newLine;
    if (s->size == 0)
    {
        newLength = 128;
        newLine = (char*) malloc (newLength);
        *newLine = '\0';
    }
    else
    {
        newLength = 2 * s->size;
        newLine = (char*) realloc (s->buffer, newLength);
    }
    if (newLine == NULL)
        perror ("string too large");
    else
    {
        s->buffer = newLine;
        s->size = newLength;
        result = 1;
    }
    return result;
}

/* Copy name of tag out of tag line */
static void copyName (tagFile *const file)
{
    size_t length;
    const char *end = strchr (file->line.buffer, '\t');
    if (end == NULL)
    {
        end = strchr (file->line.buffer, '\n');
        if (end == NULL)
            end = strchr (file->line.buffer, '\r');
    }
    if (end != NULL)
        length = end - file->line.buffer;
    else
        length = strlen (file->line.buffer);
    while (length >= file->name.size)
        growString (&file->name);
    strncpy (file->name.buffer, file->line.buffer, length);
    file->name.buffer [length] = '\0';
}

static int readTagLineRaw (tagFile *const file)
{
    int result = 1;
    int reReadLine;

    /*  If reading the line places any character other than a null or a
     *  newline at the last character position in the buffer (one less than
     *  the buffer size), then we must resize the buffer and reattempt to read
     *  the line.
     */
    do
    {
        char *const pLastChar = file->line.buffer + file->line.size - 2;
        char *line;

        file->pos = ftell (file->fp);
        reReadLine = 0;
        *pLastChar = '\0';
        line = fgets (file->line.buffer, (int) file->line.size, file->fp);
        if (line == NULL)
        {
            /* read error */
            if (! feof (file->fp))
                perror ("readTagLine");
            result = 0;
        }
        else if (*pLastChar != '\0'  &&
                    *pLastChar != '\n'  &&  *pLastChar != '\r')
        {
            /*  buffer overflow */
            growString (&file->line);
            fseek (file->fp, file->pos, SEEK_SET);
            reReadLine = 1;
        }
        else
        {
            size_t i = strlen (file->line.buffer);
            while (i > 0  &&
                   (file->line.buffer [i - 1] == '\n' || file->line.buffer [i - 1] == '\r'))
            {
                file->line.buffer [i - 1] = '\0';
                --i;
            }
        }
    } while (reReadLine  &&  result);
    if (result)
        copyName (file);
    return result;
}

static int readTagLine (tagFile *const file)
{
    int result;
    do
    {
        result = readTagLineRaw (file);
    } while (result && *file->name.buffer == '\0');
    return result;
}

static tagResult growFields (tagFile *const file)
{
    tagResult result = TagFailure;
    unsigned short newCount = (unsigned short) 2 * file->fields.max;
    tagExtensionField *newFields = (tagExtensionField*)
            realloc (file->fields.list, newCount * sizeof (tagExtensionField));
    if (newFields == NULL)
        perror ("too many extension fields");
    else
    {
        file->fields.list = newFields;
        file->fields.max = newCount;
        result = TagSuccess;
    }
    return result;
}

static void parseExtensionFields (tagFile *const file, tagEntry *const entry,
                                  char *const string)
{
    char *p = string;
    while (p != NULL  &&  *p != '\0')
    {
        while (*p == TAB)
            *p++ = '\0';
        if (*p != '\0')
        {
            char *colon;
            char *field = p;
            p = strchr (p, TAB);
            if (p != NULL)
                *p++ = '\0';
            colon = strchr (field, ':');
            if (colon == NULL)
                entry->kind = field;
            else
            {
                const char *key = field;
                const char *value = colon + 1;
                *colon = '\0';
                if (strcmp (key, "kind") == 0)
                    entry->kind = value;
                else if (strcmp (key, "file") == 0)
                    entry->fileScope = 1;
                else if (strcmp (key, "line") == 0)
                    entry->address.lineNumber = atol (value);
                else
                {
                    if (entry->fields.count == file->fields.max)
                        growFields (file);
                    file->fields.list [entry->fields.count].key = key;
                    file->fields.list [entry->fields.count].value = value;
                    ++entry->fields.count;
                }
            }
        }
    }
}

static void parseTagLine (tagFile *file, tagEntry *const entry)
{
    int i;
    char *p = file->line.buffer;
    char *tab = strchr (p, TAB);

    entry->fields.list = NULL;
    entry->fields.count = 0;
    entry->kind = NULL;
    entry->fileScope = 0;

    entry->name = p;
    if (tab != NULL)
    {
        *tab = '\0';
        p = tab + 1;
        entry->file = p;
        tab = strchr (p, TAB);
        if (tab != NULL)
        {
            int fieldsPresent;
            *tab = '\0';
            p = tab + 1;
            if (*p == '/'  ||  *p == '?')
            {
                /* parse pattern */
                int delimiter = *(unsigned char*) p;
                entry->address.lineNumber = 0;
                entry->address.pattern = p;
                do
                {
                    p = strchr (p + 1, delimiter);
                } while (p != NULL  &&  *(p - 1) == '\\');
                if (p == NULL)
                {
                    /* invalid pattern */
                }
                else
                    ++p;
            }
            else if (isdigit ((int) *(unsigned char*) p))
            {
                /* parse line number */
                entry->address.pattern = p;
                entry->address.lineNumber = atol (p);
                while (isdigit ((int) *(unsigned char*) p))
                    ++p;
            }
            else
            {
                /* invalid pattern */
            }
            fieldsPresent = (strncmp (p, ";\"", 2) == 0);
            *p = '\0';
            if (fieldsPresent)
                parseExtensionFields (file, entry, p + 2);
        }
    }
    if (entry->fields.count > 0)
        entry->fields.list = file->fields.list;
    for (i = entry->fields.count  ;  i < file->fields.max  ;  ++i)
    {
        file->fields.list [i].key = NULL;
        file->fields.list [i].value = NULL;
    }
}

static char *duplicate (const char *str)
{
    char *result = NULL;
    if (str != NULL)
    {
        result = strdup (str);
        if (result == NULL)
            perror (NULL);
    }
    return result;
}

static void readPseudoTags (tagFile *const file, tagFileInfo *const info)
{
    fpos_t startOfLine;
    const size_t prefixLength = strlen (PseudoTagPrefix);
    if (info != NULL)
    {
        info->file.format     = 1;
        info->file.sort       = TAG_UNSORTED;
        info->program.author  = NULL;
        info->program.name    = NULL;
        info->program.url     = NULL;
        info->program.version = NULL;
    }
    while (1)
    {
        fgetpos (file->fp, &startOfLine);
        if (! readTagLine (file))
            break;
        if (strncmp (file->line.buffer, PseudoTagPrefix, prefixLength) != 0)
            break;
        else
        {
            tagEntry entry;
            const char *key, *value;
            parseTagLine (file, &entry);
            key = entry.name + prefixLength;
            value = entry.file;
            if (strcmp (key, "TAG_FILE_SORTED") == 0)
                file->sortMethod = (sortType) atoi (value);
            else if (strcmp (key, "TAG_FILE_FORMAT") == 0)
                file->format = (short) atoi (value);
            else if (strcmp (key, "TAG_PROGRAM_AUTHOR") == 0)
                file->program.author = duplicate (value);
            else if (strcmp (key, "TAG_PROGRAM_NAME") == 0)
                file->program.name = duplicate (value);
            else if (strcmp (key, "TAG_PROGRAM_URL") == 0)
                file->program.url = duplicate (value);
            else if (strcmp (key, "TAG_PROGRAM_VERSION") == 0)
                file->program.version = duplicate (value);
            if (info != NULL)
            {
                info->file.format     = file->format;
                info->file.sort       = file->sortMethod;
                info->program.author  = file->program.author;
                info->program.name    = file->program.name;
                info->program.url     = file->program.url;
                info->program.version = file->program.version;
            }
        }
    }
    fsetpos (file->fp, &startOfLine);
}

static void gotoFirstLogicalTag (tagFile *const file)
{
    fpos_t startOfLine;
    const size_t prefixLength = strlen (PseudoTagPrefix);
    rewind (file->fp);
    while (1)
    {
        fgetpos (file->fp, &startOfLine);
        if (! readTagLine (file))
            break;
        if (strncmp (file->line.buffer, PseudoTagPrefix, prefixLength) != 0)
            break;
    }
    fsetpos (file->fp, &startOfLine);
}

static tagFile *initialize (const char *const filePath, tagFileInfo *const info)
{
    tagFile *result = (tagFile*) calloc ((size_t) 1, sizeof (tagFile));
    if (result != NULL)
    {
        growString (&result->line);
        growString (&result->name);
        result->fields.max = 20;
        result->fields.list = (tagExtensionField*) calloc (
            result->fields.max, sizeof (tagExtensionField));
        result->fp = fopen (filePath, "r");
        if (result->fp == NULL)
        {
            free (result);
            result = NULL;
            info->status.error_number = errno;
        }
        else
        {
            fseek (result->fp, 0, SEEK_END);
            result->size = ftell (result->fp);
            rewind (result->fp);
            readPseudoTags (result, info);
            info->status.opened = 1;
            result->initialized = 1;
        }
    }
    return result;
}

static void terminate (tagFile *const file)
{
    fclose (file->fp);

    free (file->line.buffer);
    free (file->name.buffer);
    free (file->fields.list);

    if (file->program.author != NULL)
        free (file->program.author);
    if (file->program.name != NULL)
        free (file->program.name);
    if (file->program.url != NULL)
        free (file->program.url);
    if (file->program.version != NULL)
        free (file->program.version);
    if (file->search.name != NULL)
        free (file->search.name);

    memset (file, 0, sizeof (tagFile));

    free (file);
}

static tagResult readNext (tagFile *const file, tagEntry *const entry)
{
    tagResult result;
    if (file == NULL  ||  ! file->initialized)
        result = TagFailure;
    else if (! readTagLine (file))
        result = TagFailure;
    else
    {
        if (entry != NULL)
            parseTagLine (file, entry);
        result = TagSuccess;
    }
    return result;
}

static const char *readFieldValue (
    const tagEntry *const entry, const char *const key)
{
    const char *result = NULL;
    int i;
    if (strcmp (key, "kind") == 0)
        result = entry->kind;
    else if (strcmp (key, "file") == 0)
        result = EmptyString;
    else for (i = 0  ;  i < entry->fields.count  &&  result == NULL  ;  ++i)
        if (strcmp (entry->fields.list [i].key, key) == 0)
            result = entry->fields.list [i].value;
    return result;
}

static int readTagLineSeek (tagFile *const file, const off_t pos)
{
    int result = 0;
    if (fseek (file->fp, pos, SEEK_SET) == 0)
    {
        result = readTagLine (file);  /* read probable partial line */
        if (pos > 0  &&  result)
            result = readTagLine (file);  /* read complete line */
    }
    return result;
}

static int nameComparison (tagFile *const file)
{
    int result;
    if (file->search.ignorecase)
    {
        if (file->search.partial)
            result = strnuppercmp (file->search.name, file->name.buffer,
                    file->search.nameLength);
        else
            result = struppercmp (file->search.name, file->name.buffer);
    }
    else
    {
        if (file->search.partial)
            result = strncmp (file->search.name, file->name.buffer,
                    file->search.nameLength);
        else
            result = strcmp (file->search.name, file->name.buffer);
    }
    return result;
}

static void findFirstNonMatchBefore (tagFile *const file)
{
#define JUMP_BACK 512
    int more_lines;
    int comp;
    off_t start = file->pos;
    off_t pos = start;
    do
    {
        if (pos < (off_t) JUMP_BACK)
            pos = 0;
        else
            pos = pos - JUMP_BACK;
        more_lines = readTagLineSeek (file, pos);
        comp = nameComparison (file);
    } while (more_lines  &&  comp == 0  &&  pos > 0  &&  pos < start);
}

static tagResult findFirstMatchBefore (tagFile *const file)
{
    tagResult result = TagFailure;
    int more_lines;
    off_t start = file->pos;
    findFirstNonMatchBefore (file);
    do
    {
        more_lines = readTagLine (file);
        if (nameComparison (file) == 0)
            result = TagSuccess;
    } while (more_lines  &&  result != TagSuccess  &&  file->pos < start);
    return result;
}

static tagResult findBinary (tagFile *const file)
{
    tagResult result = TagFailure;
    off_t lower_limit = 0;
    off_t upper_limit = file->size;
    off_t last_pos = 0;
    off_t pos = upper_limit / 2;
    while (result != TagSuccess)
    {
        if (! readTagLineSeek (file, pos))
        {
            /* in case we fell off end of file */
            result = findFirstMatchBefore (file);
            break;
        }
        else if (pos == last_pos)
        {
            /* prevent infinite loop if we backed up to beginning of file */
            break;
        }
        else
        {
            const int comp = nameComparison (file);
            last_pos = pos;
            if (comp < 0)
            {
                upper_limit = pos;
                pos = lower_limit + ((upper_limit - lower_limit) / 2);
            }
            else if (comp > 0)
            {
                lower_limit = pos;
                pos = lower_limit + ((upper_limit - lower_limit) / 2);
            }
            else if (pos == 0)
                result = TagSuccess;
            else
                result = findFirstMatchBefore (file);
        }
    }
    return result;
}

static tagResult findSequential (tagFile *const file)
{
    tagResult result = TagFailure;
    if (file->initialized)
    {
        while (result == TagFailure  &&  readTagLine (file))
        {
            if (nameComparison (file) == 0)
                result = TagSuccess;
        }
    }
    return result;
}

static tagResult find (tagFile *const file, tagEntry *const entry,
                       const char *const name, const int options)
{
    tagResult result;
    if (file->search.name != NULL)
        free (file->search.name);
    file->search.name = duplicate (name);
    file->search.nameLength = strlen (name);
    file->search.partial = (options & TAG_PARTIALMATCH) != 0;
    file->search.ignorecase = (options & TAG_IGNORECASE) != 0;
    fseek (file->fp, 0, SEEK_END);
    file->size = ftell (file->fp);
    rewind (file->fp);
    if ((file->sortMethod == TAG_SORTED      && !file->search.ignorecase) ||
        (file->sortMethod == TAG_FOLDSORTED  &&  file->search.ignorecase))
    {
#ifdef DEBUG
        printf ("<performing binary search>\n");
#endif
        result = findBinary (file);
    }
    else
    {
#ifdef DEBUG
        printf ("<performing sequential search>\n");
#endif
        result = findSequential (file);
    }

    if (result != TagSuccess)
        file->search.pos = file->size;
    else
    {
        file->search.pos = file->pos;
        if (entry != NULL)
            parseTagLine (file, entry);
    }
    return result;
}

static tagResult findNext (tagFile *const file, tagEntry *const entry)
{
    tagResult result;
    if ((file->sortMethod == TAG_SORTED      && !file->search.ignorecase) ||
        (file->sortMethod == TAG_FOLDSORTED  &&  file->search.ignorecase))
    {
        result = tagsNext (file, entry);
        if (result == TagSuccess  && nameComparison (file) != 0)
            result = TagFailure;
    }
    else
    {
        result = findSequential (file);
        if (result == TagSuccess  &&  entry != NULL)
            parseTagLine (file, entry);
    }
    return result;
}

/*
*  EXTERNAL INTERFACE
*/

extern tagFile *tagsOpen (const char *const filePath, tagFileInfo *const info)
{
    return initialize (filePath, info);
}

extern tagResult tagsSetSortType (tagFile *const file, const sortType type)
{
    tagResult result = TagFailure;
    if (file != NULL  &&  file->initialized)
    {
        file->sortMethod = type;
        result = TagSuccess;
    }
    return result;
}

extern tagResult tagsFirst (tagFile *const file, tagEntry *const entry)
{
    tagResult result = TagFailure;
    if (file != NULL  &&  file->initialized)
    {
        gotoFirstLogicalTag (file);
        result = readNext (file, entry);
    }
    return result;
}

extern tagResult tagsNext (tagFile *const file, tagEntry *const entry)
{
    tagResult result = TagFailure;
    if (file != NULL  &&  file->initialized)
        result = readNext (file, entry);
    return result;
}

extern const char *tagsField (const tagEntry *const entry, const char *const key)
{
    const char *result = NULL;
    if (entry != NULL)
        result = readFieldValue (entry, key);
    return result;
}

extern tagResult tagsFind (tagFile *const file, tagEntry *const entry,
                           const char *const name, const int options)
{
    tagResult result = TagFailure;
    if (file != NULL  &&  file->initialized)
        result = find (file, entry, name, options);
    return result;
}

extern tagResult tagsFindNext (tagFile *const file, tagEntry *const entry)
{
    tagResult result = TagFailure;
    if (file != NULL  &&  file->initialized)
        result = findNext (file, entry);
    return result;
}

extern tagResult tagsClose (tagFile *const file)
{
    tagResult result = TagFailure;
    if (file != NULL  &&  file->initialized)
    {
        terminate (file);
        result = TagSuccess;
    }
    return result;
}

/*
*  TEST FRAMEWORK
*/

#ifdef READTAGS_MAIN

static const char *TagFileName = "tags";
static const char *ProgramName;
static int extensionFields;
static int SortOverride;
static sortType SortMethod;

static void printTag (const tagEntry *entry)
{
    int i;
    int first = 1;
    const char* separator = ";\"";
    const char* const empty = "";
/* "sep" returns a value only the first time it is evaluated */
#define sep (first ? (first = 0, separator) : empty)
    printf ("%s\t%s\t%s",
        entry->name, entry->file, entry->address.pattern);
    if (extensionFields)
    {
        if (entry->kind != NULL  &&  entry->kind [0] != '\0')
            printf ("%s\tkind:%s", sep, entry->kind);
        if (entry->fileScope)
            printf ("%s\tfile:", sep);
#if 0
        if (entry->address.lineNumber > 0)
            printf ("%s\tline:%lu", sep, entry->address.lineNumber);
#endif
        for (i = 0  ;  i < entry->fields.count  ;  ++i)
            printf ("%s\t%s:%s", sep, entry->fields.list [i].key,
                entry->fields.list [i].value);
    }
    putchar ('\n');
#undef sep
}

static void findTag (const char *const name, const int options)
{
    tagFileInfo info;
    tagEntry entry;
    tagFile *const file = tagsOpen (TagFileName, &info);
    if (file == NULL)
    {
        fprintf (stderr, "%s: cannot open tag file: %s: %s\n",
                ProgramName, strerror (info.status.error_number), name);
        exit (1);
    }
    else
    {
        if (SortOverride)
            tagsSetSortType (file, SortMethod);
        if (tagsFind (file, &entry, name, options) == TagSuccess)
        {
            do
            {
                printTag (&entry);
            } while (tagsFindNext (file, &entry) == TagSuccess);
        }
        tagsClose (file);
    }
}

static void listTags (void)
{
    tagFileInfo info;
    tagEntry entry;
    tagFile *const file = tagsOpen (TagFileName, &info);
    if (file == NULL)
    {
        fprintf (stderr, "%s: cannot open tag file: %s: %s\n",
                ProgramName, strerror (info.status.error_number), TagFileName);
        exit (1);
    }
    else
    {
        while (tagsNext (file, &entry) == TagSuccess)
            printTag (&entry);
        tagsClose (file);
    }
}

const char *const Usage =
    "Find tag file entries matching specified names.\n\n"
    "Usage: %s [-ilp] [-s[0|1]] [-t file] [name(s)]\n\n"
    "Options:\n"
    "    -e           Include extension fields in output.\n"
    "    -i           Perform case-insensitive matching.\n"
    "    -l           List all tags.\n"
    "    -p           Perform partial matching.\n"
    "    -s[0|1|2]    Override sort detection of tag file.\n"
    "    -t file      Use specified tag file (default: \"tags\").\n"
    "Note that options are acted upon as encountered, so order is significant.\n";

extern int main (int argc, char **argv)
{
    int options = 0;
    int actionSupplied = 0;
    int i;
    ProgramName = argv [0];
    if (argc == 1)
    {
        fprintf (stderr, Usage, ProgramName);
        exit (1);
    }
    for (i = 1  ;  i < argc  ;  ++i)
    {
        const char *const arg = argv [i];
        if (arg [0] != '-')
        {
            findTag (arg, options);
            actionSupplied = 1;
        }
        else
        {
            size_t j;
            for (j = 1  ;  arg [j] != '\0'  ;  ++j)
            {
                switch (arg [j])
                {
                    case 'e': extensionFields = 1;         break;
                    case 'i': options |= TAG_IGNORECASE;   break;
                    case 'p': options |= TAG_PARTIALMATCH; break;
                    case 'l': listTags (); actionSupplied = 1; break;
            
                    case 't':
                        if (arg [j+1] != '\0')
                        {
                            TagFileName = arg + j + 1;
                            j += strlen (TagFileName);
                        }
                        else if (i + 1 < argc)
                            TagFileName = argv [++i];
                        else
                        {
                            fprintf (stderr, Usage, ProgramName);
                            exit (1);
                        }
                        break;
                    case 's':
                        SortOverride = 1;
                        ++j;
                        if (arg [j] == '\0')
                            SortMethod = TAG_SORTED;
                        else if (strchr ("012", arg[j]) != NULL)
                            SortMethod = (sortType) (arg[j] - '0');
                        else
                        {
                            fprintf (stderr, Usage, ProgramName);
                            exit (1);
                        }
                        break;
                    default:
                        fprintf (stderr, "%s: unknown option: %c\n",
                                    ProgramName, arg[j]);
                        exit (1);
                        break;
                }
            }
        }
    }
    if (! actionSupplied)
    {
        fprintf (stderr,
            "%s: no action specified: specify tag name(s) or -l option\n",
            ProgramName);
        exit (1);
    }
    return 0;
}

#endif

/* vi:set tabstop=4 shiftwidth=4: */
