/*
 * Back-end misc module
 * See "diff.h" for the details of data structure.
 * This module should be independent from GUI frontend.
 *
 * Copyright INOUE Seiichiro <inoue@ainet.or.jp>, licensed under the GPL.
 */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <sys/stat.h>
#include <unistd.h>
#include "diff.h"


/* NOTE:
 * Most of the routines doesn't modify DiffFiles argument.
 * However, I can't specify 'const' modifier,
 * because dfiles_get_fileinfo() requires 'non-const' argument.
 * Refer to "diffdata.c" about why dfiles_get_fileinfo() does so.
 */

/**
 * dfiles_get_status:
 * See "diff.h" about enum FilesStatus.
 * No need to check fi3.
 **/
FilesStatus
dfiles_get_status(DiffFiles *dfiles)
{
	const FileInfo *fi1 = dfiles_get_fileinfo(dfiles, FIRST_FILE, FALSE);
	const FileInfo *fi2 = dfiles_get_fileinfo(dfiles, SECOND_FILE, FALSE);

	/* Checking order does matter */
	if (dfiles->binary)
		return BINARY_FILES;
	if (fi1->fname[0] == '\0') 
		return ONLY_FILE2_EXISTS;
	if (fi2->fname[0] == '\0')
		return ONLY_FILE1_EXISTS;
	if (fi1->f_dir == TRUE) {
		/* double check */
		if (fi2->f_dir == FALSE) {
			g_warning("something wrong in dfiles_get_status()\n");
		}
		return DIRECTORIES;
	}
	if (dfiles->dlines_list == NULL)
		return IDENTICAL_FILES;

	return DIFFERENT_FILES;
}

/**
 * dfiles_has_file_modified:
 * Check the files have been modified.
 * If a file has been modified by the other process,
 * mmap'ed memory is also modified.
 * Some operations depend on mmap'ed memory, so this check is necessary.
 * Checking only mtime is insufficient,
 * because you can change mtime to arbitrary value, e.g. by 'touch' command.
 **/
FileModStatue
dfiles_has_file_modified(DiffFiles *dfiles)
{
	int n;

	/* This function doesn't matter unless they are comparable files. */
	if (dfiles_get_status(dfiles) != DIFFERENT_FILES)
		return MOD_DONTCARE;

	for (n = 0; n < MAX_NUM_COMPARE_FILES; n++) {
		const FileInfo *fi = dfiles_get_fileinfo(dfiles, n, FALSE);
		struct stat sb;
		
		if (!fi->fname[0])
			continue;
		if (stat(fi->fname, &sb) == -1) {
			g_warning("%s: stat in dfiles_is_file_modified()", fi->fname);
			return MOD_ERROR;
		}
		if (sb.st_mtime > fi->mtime || sb.st_ctime > fi->ctime)
			return MOD_MODIFIED;
	}

	return MOD_NOT_MODIFIED;
}

/**
 * dfiles_calc_total_nlines:
 * Calculate the tolal number of different lines, and return it.
 * Note: in diff3 case, the third dlines->nlines is zero.
 **/
int
dfiles_calc_total_nlines(const DiffFiles *dfiles, WhichFile n)
{
	GList *list;/* Doubly linked list of DiffLines */
	int ret_nlines = 0;

	for (list = dfiles->dlines_list; list; list = list->next) {
		DiffLines *dlines = list->data;
		
		if (n == FIRST_FILE &&
			(dlines->difftype & F2ONLY || dlines->difftype & F3ONLY
			 || dlines->difftype & F23ADD))
			continue;
		if (n == SECOND_FILE &&
			(dlines->difftype & F1ONLY || dlines->difftype & F3ONLY
			 || dlines->difftype & F31ADD))
			continue;
		if (n == THIRD_FILE &&
			(dlines->difftype & F1ONLY || dlines->difftype & F2ONLY
			 || dlines->difftype & F12ADD))
			continue;
		
		ret_nlines += dlines->between[n].end - dlines->between[n].begin + 1; 
	}
	
	return ret_nlines;
}


/**
 * dfiles_get_max_nlines:
 * Compare the number of lines of thefiles, and return one of the bigger.
 * Input:
 * (const)DiffFiles *dfiles;
 * Output:
 * Return value; The number of lines of the bigger.
 **/
int
dfiles_get_max_nlines(DiffFiles *dfiles)
{
	const FileInfo *fi1 = dfiles_get_fileinfo(dfiles, FIRST_FILE, TRUE);
	const FileInfo *fi2 = dfiles_get_fileinfo(dfiles, SECOND_FILE, TRUE);
	const FileInfo *fi3 = dfiles_get_fileinfo(dfiles, THIRD_FILE, TRUE);
	int tmp;

	tmp = (fi1->nlines > fi2->nlines) ? fi1->nlines : fi2->nlines;
	return (tmp > fi3->nlines) ? tmp : fi3->nlines;
}



/*
 * DiffFindFunc functions:
 * Using the current difference, find a specified difference,
 * and return it.
 * The return value is an internal data,
 * so it shouldn't be modified by the caller.
 * Input:
 * const DiffFiles *dfiles;
 * const GList *cur_dlines_node; the current difference.
 * Output:
 * Return value; GList of DiffLines
 */

/**
 * dfiles_get_curl:
 * Return the current different lines.
 **/
const GList*
dfiles_get_curl(const DiffFiles *dfiles, const GList *cur_dlines_node)
{
	return cur_dlines_node;
}

/**
 * dfiles_get_firstl:
 * Return the first different lines.
 **/
const GList*
dfiles_get_firstl(const DiffFiles *dfiles, const GList *cur_dlines_node)
{
	if (cur_dlines_node)
		return g_list_first((GList*)cur_dlines_node);
	else
		return dfiles->dlines_list;
}

/**
 * dfiles_get_lastl:
 * Return the last different lines.
 **/
const GList*
dfiles_get_lastl(const DiffFiles *dfiles, const GList *cur_dlines_node)
{
	if (cur_dlines_node)
		return g_list_last((GList*)cur_dlines_node);
	else
		return g_list_last(dfiles->dlines_list);
}

/**
 * dfiles_find_nextl:
 * Return the next different lines.
 **/
const GList*
dfiles_find_nextl(const DiffFiles *dfiles, const GList *cur_dlines_node)
{
	if (cur_dlines_node)
		return g_list_next((GList*)cur_dlines_node);
	else
		return dfiles->dlines_list;/* first one */
}

/**
 * dfiles_find_prevl:
 * Return the previous different lines.
 **/
const GList*
dfiles_find_prevl(const DiffFiles *dfiles, const GList *cur_dlines_node)
{
	if (cur_dlines_node)
		return g_list_previous((GList*)cur_dlines_node);
	else
		return g_list_last(dfiles->dlines_list);
}


/**
 * dfiles_find_rel_curl:
 * Return the _relative_ current different lines.
 **/
const GList*
dfiles_find_rel_curl(const DiffFiles *dfiles, WhichFile n, int cur_line)
{
	const GList *list;/* Doubly linked list of DiffLines */
	
	for (list = dfiles->dlines_list; list; list = list->next) {
		const DiffLines *dlines = list->data;
		if (dlines->between[n].begin == cur_line) {
			return list;
		}
	}
	return NULL;
}

/**
 * dfiles_find_rel_nextl:
 * Return the _relative_ next different lines.
 **/
const GList*
dfiles_find_rel_nextl(const DiffFiles *dfiles, WhichFile n, int cur_line)
{
	const GList *list;/* Doubly linked list of DiffLines */
	
	for (list = dfiles->dlines_list; list; list = list->next) {
		const DiffLines *dlines = list->data;
		if (dlines->between[n].begin > cur_line) {
			return list;
		}
	}
	return NULL;
}

/**
 * dfiles_find_rel_prevl:
 * Return the _relative_ previous different lines.
 **/
const GList*
dfiles_find_rel_prevl(const DiffFiles *dfiles, WhichFile n, int cur_line)
{
	const GList *list;/* Doubly linked list of DiffLines */
	const GList *prev_list; 
	
	for (list = prev_list = dfiles->dlines_list; list; list = list->next) {
		const DiffLines *dlines = list->data;
		if (dlines->between[n].end > cur_line) {
			return prev_list;
		}
		prev_list = list;
	}
	return NULL;
}


/**
 * dfiles_find_includel:
 * Return the different lines that includes @cur_line.
 **/
const GList*
dfiles_find_includel(const DiffFiles *dfiles, WhichFile n, int cur_line)
{
	const GList *list;/* Doubly linked list of DiffLines */
	
	for (list = dfiles->dlines_list; list; list = list->next) {
		const DiffLines *dlines = list->data;
		if (dlines->between[n].begin <= cur_line
			&& cur_line <= dlines->between[n].end) {
			return list;
		}
	}
	return NULL;
}