#ifndef _VOLK_PARSER_COMMON_H
#define _VOLK_PARSER_COMMON_H

#include "volksdata/codec.h"


/** @brief TTL is UTF-8 encoded.
 *
 * @sa https://www.w3.org/TeamSubmission/turtle/#sec-grammar
 *
 * `char` should be considered to be UTF-8 throughout this library, however,
 * setting YYCTYPE to char generates case labels outside of the char range.
 */
#define YYCTYPE     uint8_t
#define YYCURSOR    it->cur
#define YYMARKER    it->mar
#define YYLIMIT     it->lim
#define YYFILL      fill(it) == 0


typedef struct {
    FILE          * fh;         ///< Input file handle.
    const char    * sh;         ///< Input string. Exclusive with fh.
    size_t          buf_size;   ///< Initial allocation for buffer.
    YYCTYPE       * buf,        ///< Start of buffer.
                  * lim,        ///< Position after the last available
                                ///<   input character (YYLIMIT).
                  * cur,        ///< Next input character to be read (YYCURSOR)
                  * mar,        ///< Most recent match (YYMARKER)
                  * tok,        ///< Start of current token.
                  * bol;        ///< Address of the beginning of the
                                ///<   current line (for debugging).
    unsigned        line;       ///< Current line no. (for debugging).
    unsigned        ct;         ///< Number of statements parsed.
    bool            eof;        ///< if we have reached EOF.
    /*!stags:re2c format = "YYCTYPE *@@;"; */
} ParseIterator;


static int fill(ParseIterator *it);


/** @brief Initialize parser.
 *
 * @param[in] it iterator handle to be initialized.
 *
 * @param[in] fh Open file handle to read from. This is exclusive with sh. If
 *  both fh and sh are provided, fh has precedence.
 *
 * @param[in] sh String to read from. This is exclusive with fh.
 */
static void parse_init (ParseIterator *it, FILE *fh, const char *sh)
{
    if(fh) {
        // Stream handling. It engages YYFILL and reads by chunks.
        it->fh = fh;
        it->sh = NULL;
        it->buf_size = CHUNK_SIZE;
        it->buf = malloc(it->buf_size);
        if (!it->buf) log_error ("Error allocating lexer buffer.");
        it->cur = it->mar = it->tok = it->lim = it->buf + it->buf_size - 1;
        it->bol = it->buf;
        it->eof = false;
        it->lim[0] = 0;
    } else {
        // String handling. Uses the provided string as the buffer.
        it->fh = NULL;
        it->sh = sh;
        it->buf_size = strlen(sh) + 1;
        it->buf = NULL;
        it->cur = it->tok = (YYCTYPE*)it->sh;
        it->lim = it->mar = it->cur + it->buf_size - 1;
        it->bol = it->cur;
        it->eof = true;
    }
    it->line = 1;
    it->ct = 0;
    /*!stags:re2c format = "it->@@ = NULL; "; */
}


int
fill(ParseIterator *it)
{
    log_debug ("Filling codec buffer @ %p.", it->buf);
    if (it->eof) return 1;

    size_t shift = it->tok - it->buf;
    size_t used = it->lim - it->tok;

    // If buffer is too small for the lexeme, double the capacity.
    if (shift < 1) {
        YYCTYPE *old_buf = it->buf;
        shift += it->buf_size;
        it->buf_size *= 2;
        LOG_DEBUG ("Reallocating buffer to %zu bytes.", it->buf_size);
        it->buf = realloc (it->buf, it->buf_size);
        if (!it->buf) {
            log_error ("Memory allocation error.");
            return -1;
        }
        // Move all relative points if address changed.
        size_t reloc_off = it->buf - old_buf;
        it->cur += reloc_off;
        it->tok += reloc_off;
        it->lim += reloc_off;
        it->mar += reloc_off;
    } else {
        LOG_DEBUG("Shifting bytes: %zu", shift);
        memmove (it->buf, it->tok, used);
        LOG_TRACE ("Limit offset before reading data: %zu", it->lim - it->tok);
        it->lim -= shift;
        it->cur -= shift;
        it->mar -= shift;
        it->tok -= shift;
    }
    it->lim += fread (it->lim, 1, it->buf_size - used - 1, it->fh);
    /*!stags:re2c format = "if (it->@@) it->@@ -= shift; "; */
    LOG_TRACE ("Cursor offset from last token: %zu", it->cur - it->tok);
    LOG_TRACE ("Limit offset from last token: %zu", it->lim - it->tok);
    it->lim[0] = 0;
    it->eof = it->lim < it->buf + it->buf_size - 1;
    return 0;
}


#endif // _VOLK_PARSER_COMMON_H