#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include "wgrib2.h"

/*
 * a simple extension to fopen
 *
 * if file is already open, just return the pointer to the file handler
 *
 * public domain 2/2008 Wesley Ebisuzaki
 *  v1.1 WNE: upgrade: add read/write detection
 *		- can be stdin and stdout (in previous version)
 *		if pipe - set flush_mode, error checking
 *  v1.2 10/2014 John Howard .. add ffclose
 *               needs to keep track of number of ffopens of a file
 *               when number ffopens and ffclose are the same .. close file
 *
 *               adding ffcloses is needed to make wgrib2 a callable subroutine
 *                otherwise run out of file handles
 *
 *  v1.3 4/2015 WNE added @tmp:XXXX  temporary files, added for callable wgrib2
 *                        @mem:N
 v  v1.4 7/2020 WNE, George Trojan, fixed ffopen()
 */

extern int flush_mode;
struct opened_file
{
    char *name;
    FILE *handle;
    int is_read_file;
    int usage_count;
    int do_not_close_flag;
    struct opened_file *next;
};

/* memory buffers */
extern size_t mem_buffer_pos[N_mem_buffers];

/* do not initialize opened_file_start in init_globals */
static struct opened_file *opened_file_start = NULL;
/* do not initialize opened_file_start in init_globals */

FILE *ffopen(const char *filename, const char *mode)
{
    struct opened_file *ptr;
    struct stat stat_buf;  /* test for pipes */
    int is_read_file, is_write_file, is_append_file, i, len;
    const char *p;

    /* see if is a read/write file */
    is_read_file = is_write_file = is_append_file = 0;
    p = mode;
    while (*p) {
	if (*p == 'r') is_read_file = 1;
	if (*p == 'w') is_write_file = 1;
	if (*p++ == 'a') is_append_file = 1;
    }
    if (is_read_file + is_write_file + is_append_file != 1) 
        fatal_error("ffopen: mode is bad %s", mode);

    if (strcmp(filename,"-") == 0) {
	if (is_read_file) return stdin;
	flush_mode = 1;
	return stdout;
    }

    if (strncmp(filename,"@mem:",5) == 0) {
	fatal_error("ffopen option does not suport memory files %s", filename);
    }

    /* see if file has already been opened */
	
    ptr = opened_file_start;
    while (ptr != NULL) {
	if (strcmp(filename,ptr->name) == 0) {
	    
            /* ptr->usage_count   should be zero at start of wgrib2 call
               ptr->is_read_flag, file was opened in read mode
               have to check if the open was for previous wgrib2 call
            */

	    /* already open in r/r or (aw)/(aw) modes */
            if (is_read_file == ptr->is_read_file) {
	        (ptr->usage_count)++;
	        return ptr->handle;
            }

	    /* already being used in incompatible mode do not allow r+ w+ or a+ modes */
            if (ptr->usage_count > 0) {
		fatal_error("ffopen: file %s cannot be used for for read and write at same time", ptr->name);
	    }

            /* open a file that has been opened before but not in use */
	    /*
	    ptr->handle = freopen(NULL,mode, ptr->handle);
	    if (!ptr->handle) fatal_error("ffopen: wgrib2 could not freopen %s", ptr->name);
	    */
 	    /* brute force. close file first. Since not in use, can change ptr->handle */
	    i = fclose(ptr->handle);
	    if (i) fprintf(stderr,"Warning ffopen(%s): closing used file, fclose() failed fclose err=%d\n",ptr->name, i);
	    ptr->handle = fopen(ptr->name, mode);
	    if (ptr->handle == NULL) fatal_error("ffopen: failed to reopen %s\n", ptr->name);
	    ptr->is_read_file = is_read_file;
	    ptr->usage_count = 1;
	    return ptr->handle;
	}
	ptr = ptr->next;
    }

    ptr = (struct opened_file *) malloc( sizeof(struct opened_file) );
    if (ptr == NULL) fatal_error("ffopen: memory allocation problem (%s)", filename);
    len = strlen(filename) + 1;
    ptr->name = (char *) malloc(len);
    if (ptr->name == NULL) fatal_error("ffopen: memory allocation problem (%s)", filename);

    strncpy(ptr->name, filename, len);
    ptr->is_read_file = is_read_file;
    ptr->usage_count = 1;
    ptr->do_not_close_flag = 1;		// default is not to close file file

    /* check if filename is @tmp:XXX or just XXX */
    if (strlen(filename) > 5 && strncmp(filename, "@tmp:", 5) == 0) {
	if (is_read_file) {
	    /* remove ptr */
	    free(ptr->name);
	    free(ptr);
	    fatal_error("ffopen: creating temporary file for read is not a good idea (%s)", filename);
	}
        ptr->handle = tmpfile();	/* ISO C to generate temporary file */
        if (ptr->handle == NULL) {
	    /* remove ptr */
	    free(ptr->name);
	    free(ptr);
	    fatal_error("ffopen: could not open tmpfile %s", filename);
	}
        /* add ptr to linked list */
        ptr->next = opened_file_start;
        opened_file_start = ptr;
        return ptr->handle;
    }

    /* disk file or pipe */
    ptr->handle = fopen(filename,mode);
    if (ptr->handle == NULL) {
	free(ptr->name);
	free(ptr);
	// fatal_error("ffopen: could not open %s", filename);
	return NULL;
    }

    /* check if output is to a pipe */
    if (is_read_file == 0) {
	if (stat(filename, &stat_buf) == -1) {
	    /* remove ptr */
	    free(ptr->name);
	    free(ptr);
	    fatal_error("ffopen: could not stat file: %s", filename);
	}
        if (S_ISFIFO(stat_buf.st_mode)) {
	    flush_mode  = 1;
	}
    }

    /* add ptr to linked list */
    ptr->next = opened_file_start;
    opened_file_start = ptr;
    return ptr->handle;
}

int ffclose(FILE *flocal)
{
    struct opened_file *ptr, *last_ptr;

    if (flocal == stdin || flocal == stdout) return 0;		// do not close stdin or stdout

    last_ptr = NULL;
    ptr = opened_file_start;
    while (ptr != NULL) {
	if (ptr->handle == flocal) {
	    if (ptr->usage_count <= 0) fatal_error_i("ffclose: usage_count = %d <= 0, %d", ptr->usage_count);
	    if (--ptr->usage_count == 0) {   // usage_count is zero, can close file name
	        if (ptr->do_not_close_flag == 1) return 0;
		if (last_ptr == NULL)
		    opened_file_start = ptr->next;
		else {
		    last_ptr->next = ptr->next;
		}
		fclose(ptr->handle);
		free(ptr->name);
		free(ptr);
	    }
	    return 0;
	}
	last_ptr = ptr;
	ptr = ptr->next;
    }
    return 1;	/* not found */
}

/*
 * make a file that has been opened with ffopen persistent
 *
 * with a callable wgrib2, may not want to close files for performance
 *
 */
int mk_file_persistent(const char *filename) {
    struct opened_file *ptr;

    ptr = opened_file_start;
    while (ptr != NULL) {
	if (strcmp(filename,ptr->name) == 0) {
	    ptr->do_not_close_flag = 1;
	    return 0;
	}
	ptr = ptr->next;
    }
    fprintf(stderr,"Warning persistant flag not set %s\n", filename);
    return 0;
}
int mk_file_transient(const char *filename) {
    struct opened_file *ptr;

    ptr = opened_file_start;
    while (ptr != NULL) {
	if (strcmp(filename,ptr->name) == 0) {
	    ptr->do_not_close_flag = 0;
	    return 0;
	}
	ptr = ptr->next;
    }
    fprintf(stderr,"Warning transient flag not set %s\n", filename);
    return 0;
}

/*
 * remove file from ffopen() linked lists
 * old: delete file not in use
 * 5/2020 close file
 * 6/2020 reset memory file
 *
 * NOTE: must mever be called by wgrib2 when file is in use
 *  should only be called by external program (not reentrent)
 */

int wgrib2_free_file(const char *filename) {
    struct opened_file *ptr, *last_ptr;
    int i;

    /* if valid @mem:XX file */
    if (strncmp(filename,"@mem:",5) == 0) {
        i = atoi(filename+5);
        if (i == 0 && filename[5] != '0') i = -1;
        if (i >= 0 && i < N_mem_buffers) {
            new_mem_buffer(i, 0);
            return 0;
        }
    }

    // status_ffopen();
    ptr = opened_file_start;
    last_ptr = NULL;
    while (ptr != NULL) {
	if (strcmp(filename,ptr->name) == 0) {
	    /* delete file entry */
	    if (last_ptr == NULL)	// ptr is first entry
		opened_file_start = ptr->next;
	    else {
		last_ptr->next = ptr->next;
	    }
	    fclose(ptr->handle);
	    free(ptr->name);
	    free(ptr);
	    return 0;
	}
	last_ptr = ptr;
	ptr = ptr->next;
    }
    // fprintf(stderr,"Warning wgrib2_free_file: %s not found\n", filename);
    return 1;
}

/*
 * rewind filename
 */

int rewind_file(const char *filename) {
    struct opened_file *ptr;
    int i;

    if (strncmp(filename,"@mem:",5) == 0) {
        i = atoi(filename+5);
        if (i < 0 || i >= N_mem_buffers || (i == 0 && filename[5] != '0')) {
            fatal_error_i("rewind_file: @mem:N  N from 0..%d", N_mem_buffers-1);
        }
        mem_buffer_pos[i] = 0;
        return 0;
    }

    ptr = opened_file_start;
    while (ptr != NULL) {
	if (strcmp(filename,ptr->name) == 0) {
            if (fseek(ptr->handle, 0L, SEEK_SET))
		fatal_error("rewind_file: failed (%s)", filename);
	    return 0;
	}
	ptr = ptr->next;
    }
    return 1;
}


/*
 * status of ffopen/ffclose
 */

void status_ffopen(void) {
    struct opened_file *ptr;
    ptr = opened_file_start;
    while (ptr != NULL) {
        fprintf(stderr, "file: %s %c:%s file_offset=%ld usage=%d\n", ptr->name, ptr->is_read_file ? 'r' : 'w', 
		ptr->do_not_close_flag ? "perm":"tran", ftell(ptr->handle), ptr->usage_count);
	ptr = ptr->next;
    }
    return;
}