/*********************************************************************
 * bfs                                                               *
 * Copyright (C) 2015-2016 Tavian Barnes <tavianator@tavianator.com> *
 *                                                                   *
 * This program is free software. It comes without any warranty, to  *
 * the extent permitted by applicable law. You can redistribute it   *
 * and/or modify it under the terms of the Do What The Fuck You Want *
 * To Public License, Version 2, as published by Sam Hocevar. See    *
 * the COPYING file or http://www.wtfpl.net/ for more details.       *
 *********************************************************************/

#include "bfs.h"
#include "bftw.h"
#include <assert.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <fnmatch.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <time.h>
#include <unistd.h>

struct eval_state {
	/** Data about the current file. */
	struct BFTW *ftwbuf;
	/** The parsed command line. */
	const struct cmdline *cmdline;
	/** The bftw() callback return value. */
	enum bftw_action action;
	/** The eval_cmdline() return value. */
	int ret;
	/** A stat() buffer, if necessary. */
	struct stat statbuf;
};

/**
 * Report an error that occurs during evaluation.
 */
static void eval_error(struct eval_state *state) {
	pretty_error(state->cmdline->stderr_colors,
	             "'%s': %s\n", state->ftwbuf->path, strerror(errno));
	state->ret = -1;
}

/**
 * Perform a stat() call if necessary.
 */
static const struct stat *fill_statbuf(struct eval_state *state) {
	struct BFTW *ftwbuf = state->ftwbuf;
	if (!ftwbuf->statbuf) {
		if (fstatat(ftwbuf->at_fd, ftwbuf->at_path, &state->statbuf, ftwbuf->at_flags) == 0) {
			ftwbuf->statbuf = &state->statbuf;
		} else {
			eval_error(state);
		}
	}
	return ftwbuf->statbuf;
}

/**
 * Get the difference (in seconds) between two struct timespecs.
 */
static time_t timespec_diff(const struct timespec *lhs, const struct timespec *rhs) {
	time_t ret = lhs->tv_sec - rhs->tv_sec;
	if (lhs->tv_nsec < rhs->tv_nsec) {
		--ret;
	}
	return ret;
}

/**
 * Perform a comparison.
 */
static bool do_cmp(const struct expr *expr, int n) {
	switch (expr->cmp) {
	case CMP_EXACT:
		return n == expr->idata;
	case CMP_LESS:
		return n < expr->idata;
	case CMP_GREATER:
		return n > expr->idata;
	}

	return false;
}

/**
 * -true test.
 */
bool eval_true(const struct expr *expr, struct eval_state *state) {
	return true;
}

/**
 * -false test.
 */
bool eval_false(const struct expr *expr, struct eval_state *state) {
	return false;
}

/**
 * -executable, -readable, -writable tests.
 */
bool eval_access(const struct expr *expr, struct eval_state *state) {
	struct BFTW *ftwbuf = state->ftwbuf;
	return faccessat(ftwbuf->at_fd, ftwbuf->at_path, expr->idata, ftwbuf->at_flags) == 0;
}

/**
 * -[acm]{min,time} tests.
 */
bool eval_acmtime(const struct expr *expr, struct eval_state *state) {
	const struct stat *statbuf = fill_statbuf(state);
	if (!statbuf) {
		return false;
	}

	const struct timespec *time = NULL;
	switch (expr->timefield) {
	case ATIME:
		time = &statbuf->st_atim;
		break;
	case CTIME:
		time = &statbuf->st_ctim;
		break;
	case MTIME:
		time = &statbuf->st_mtim;
		break;
	}
	assert(time);

	time_t diff = timespec_diff(&expr->reftime, time);
	switch (expr->timeunit) {
	case MINUTES:
		diff /= 60;
		break;
	case DAYS:
		diff /= 60*60*24;
		break;
	}

	return do_cmp(expr, diff);
}

/**
 * -[ac]?newer tests.
 */
bool eval_acnewer(const struct expr *expr, struct eval_state *state) {
	const struct stat *statbuf = fill_statbuf(state);
	if (!statbuf) {
		return false;
	}

	const struct timespec *time = NULL;
	switch (expr->timefield) {
	case ATIME:
		time = &statbuf->st_atim;
		break;
	case CTIME:
		time = &statbuf->st_ctim;
		break;
	case MTIME:
		time = &statbuf->st_mtim;
		break;
	}
	assert(time);

	return time->tv_sec > expr->reftime.tv_sec
		|| (time->tv_sec == expr->reftime.tv_sec && time->tv_nsec > expr->reftime.tv_nsec);
}

/**
 * -gid test.
 */
bool eval_gid(const struct expr *expr, struct eval_state *state) {
	const struct stat *statbuf = fill_statbuf(state);
	if (!statbuf) {
		return false;
	}

	return do_cmp(expr, statbuf->st_gid);
}

/**
 * -uid test.
 */
bool eval_uid(const struct expr *expr, struct eval_state *state) {
	const struct stat *statbuf = fill_statbuf(state);
	if (!statbuf) {
		return false;
	}

	return do_cmp(expr, statbuf->st_uid);
}

/**
 * -delete action.
 */
bool eval_delete(const struct expr *expr, struct eval_state *state) {
	struct BFTW *ftwbuf = state->ftwbuf;

	int flag = 0;
	if (ftwbuf->typeflag == BFTW_DIR) {
		flag |= AT_REMOVEDIR;
	}

	if (unlinkat(ftwbuf->at_fd, ftwbuf->at_path, flag) != 0) {
		eval_error(state);
		return false;
	}

	return true;
}

/**
 * -empty test.
 */