/**
 * @file
 * @brief single-source distance filter
 */

/*************************************************************************
 * Copyright (c) 2011 AT&T Intellectual Property 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors: Details at https://graphviz.org
 *************************************************************************/

#include "config.h"

#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <cgraph/cgraph.h>
#include <cgraph/ingraphs.h>
#include <getopt.h>
#include <util/agxbuf.h>
#include <util/alloc.h>
#include <util/exit.h>
#include <util/gv_math.h>
#include <util/unreachable.h>

static char *CmdName;
static char **Files;
static char **Nodes;
static bool setall;		/* if false, don't set dist attribute for
				 * nodes in different components.
				 */
static bool doPath;		/* if true, record shortest paths */
static bool doDirected;	/* if true, use directed paths */
static Agsym_t *len_sym;

typedef struct {
    Agrec_t hdr;
    double dist;		/* always positive for scanned nodes */
    Agnode_t* prev;
    bool done; ///< true if finished
} nodedata_t;

static double getlength(Agedge_t * e)
{
    double len;
    char*  lens;
    char*  p;

    if (len_sym && (*(lens = agxget(e, len_sym)))) {
	len = strtod (lens, &p);
	if (len < 0 || p == lens)
	    len = 1;
    }
    else
	len = 1;
    return len;
}

static double getdist(Agnode_t * n)
{
    nodedata_t *const data =
      (nodedata_t *)((char *)n->base.data - offsetof(nodedata_t, hdr));
    return data->dist;
}

static void setdist(Agnode_t * n, double dist)
{
    nodedata_t *const data =
      (nodedata_t *)((char *)n->base.data - offsetof(nodedata_t, hdr));
    data->dist = dist;
}

#define getprev(n) (((nodedata_t*)((n)->base.data))->prev)
#define setprev(n,p) (((nodedata_t*)((n)->base.data))->prev = (p))
#define isDone(n) (((nodedata_t*)((n)->base.data))->done)
#define setDone(n) (((nodedata_t*)((n)->base.data))->done = true)

static int cmpf(void *key1, void *key2) {
    const double dist1 = getdist(key1);
    const double dist2 = getdist(key2);
    if (dist1 < dist2)
	return -1;
    if (dist1 > dist2)
	return 1;
    if (key1 < key2)
	return -1;
    if (key1 > key2)
	return 1;
    return 0;
}

static Dtdisc_t MyDisc = {
    0,				/* int key */
    0,				/* int size */
    -1,				/* int link */
    0,				/* Dtmake_f makef */
    0,				/* Dtfree_f freef */
    cmpf,			/* Dtcompar_f comparf */
};

static Agnode_t *extract_min(Dict_t * Q)
{
    Agnode_t *rv;
    rv = dtfirst(Q);
    dtdelete(Q, rv);
    return rv;
}

static void update(Dict_t * Q, Agnode_t * dest, Agnode_t * src, double len)
{
    double newlen = getdist(src) + len;
    double oldlen = getdist(dest);

    if (is_exactly_zero(oldlen)) { // first time to see dest
	setdist(dest, newlen);
	if (doPath) setprev(dest, src);
	dtinsert(Q, dest);
    } else if (newlen < oldlen) {
	dtdelete(Q, dest);
	setdist(dest, newlen);
	if (doPath) setprev(dest, src);
	dtinsert(Q, dest);
    }
}

static void pre(Agraph_t * g)
{
    len_sym = agattr_text(g, AGEDGE, "len", NULL);
    aginit(g, AGNODE, "dijkstra", sizeof(nodedata_t), true);
}

static void post(Agraph_t * g)
{
    Agnode_t *v;
    Agnode_t *prev;
    agxbuf buf = {0};
    agxbuf dflt_buf = {0};
    Agsym_t *sym;
    Agsym_t *psym = NULL;
    double dist, oldmax;
    double maxdist = 0.0;	/* maximum "finite" distance */

    sym = agattr_text(g, AGNODE, "dist", "");
    if (doPath)
	psym = agattr_text(g, AGNODE, "prev", "");

    if (setall)
	agxbprint(&dflt_buf, "%.3lf", HUGE_VAL);
    const char *const dflt = agxbuse(&dflt_buf);

    for (v = agfstnode(g); v; v = agnxtnode(g, v)) {
	dist = getdist(v);
	if (!is_exactly_zero(dist)) {
	    dist--;
	    agxbprint(&buf, "%.3lf", dist);
	    agxset(v, sym, agxbuse(&buf));
	    if (doPath && (prev = getprev(v)))
		agxset(v, psym, agnameof(prev));
	    if (maxdist < dist)
		maxdist = dist;
	} else if (setall)
	    agxset(v, sym, dflt);
    }

    sym = agattrsym(g, "maxdist");
    if (sym) {
	if (!setall) {
	    /* if we are preserving distances in other components,
	     * check previous value of maxdist.
	     */
	    oldmax = atof(agxget(g, sym));
	    if (oldmax > maxdist)
		maxdist = oldmax;
	}
	agxbprint(&buf, "%.3lf", maxdist);
	agxset(g, sym, agxbuse(&buf));
    } else {
	agxbprint(&buf, "%.3lf", maxdist);
	agattr_text(g, AGRAPH, "maxdist", agxbuse(&buf));
    }

    agxbfree(&dflt_buf);
    agxbfree(&buf);
    agclean(g, AGNODE, "dijkstra");
    agclean(g, AGEDGE, "dijkstra");
}

static void dijkstra(Dict_t * Q, Agraph_t * G, Agnode_t * n)
{
    Agnode_t *u;
    Agedge_t *e;

    pre(G);
    setdist(n, 1);
    dtinsert(Q, n);
    if (doDirected) {
	while ((u = extract_min(Q))) {
	    setDone (u);
	    for (e = agfstout(G, u); e; e = agnxtout(G, e)) {
		if (!isDone(e->node)) update(Q, e->node, u, getlength(e));
	    }
	}
    } else {
	while ((u = extract_min(Q))) {
	    setDone (u);
	    for (e = agfstedge(G, u); e; e = agnxtedge(G, e, u)) {
		if (!isDone(e->node)) update(Q, e->node, u, getlength(e));
	    }
	}
    }
    post(G);
}

static char *useString =
    "Usage: dijkstra [-ap?] <node> [<file> <node> <file>]\n\
  -a - for nodes in a different component, set dist very large\n\
  -d - use forward directed edges\n\
  -p - attach shortest path info\n\
  -? - print usage\n\
If no files are specified, stdin is used\n";

static void usage(int v)
{
    printf("%s",useString);
    graphviz_exit(v);
}

static void init(int argc, char *argv[])
{
    int i, j, c;

    CmdName = argv[0];
    opterr = 0;
    while ((c = getopt(argc, argv, "adp?")) != -1) {
	switch (c) {
	case 'a':
	    setall = true;
	    break;
	case 'd':
	    doDirected = true;
	    break;
	case 'p':
	    doPath = true;
	    break;
	case '?':
	    if (optopt == '\0' || optopt == '?')
		usage(0);
	    else {
		fprintf(stderr, "%s: option -%c unrecognized\n",
			CmdName, optopt);
		usage(1);
	    }
	    break;
	default:
	    UNREACHABLE();
	}
    }
    argv += optind;
    argc -= optind;

    if (argc == 0) {
	fprintf(stderr, "%s: no node specified\n", CmdName);
	usage(1);
    }
    Files = gv_calloc((size_t)argc / 2 + 2, sizeof(char *));
    Nodes = gv_calloc((size_t)argc / 2 + 2, sizeof(char *));
    for (j = i = 0; i < argc; i++) {
	Nodes[j] = argv[i++];
	Files[j] = argv[i] ? argv[i] : "-";
	j++;
    }
    Nodes[j] = Files[j] = NULL;
}

int main(int argc, char **argv)
{
    Agraph_t *g;
    Agnode_t *n;
    ingraph_state ig;
    size_t i = 0;
    int code = 0;
    Dict_t *Q;

    init(argc, argv);
    newIngraph(&ig, Files);

    Q = dtopen(&MyDisc, Dtoset);
    while ((g = nextGraph(&ig)) != 0) {
	dtclear(Q);
	if ((n = agnode(g, Nodes[i], 0)))
	    dijkstra(Q, g, n);
	else {
	    fprintf(stderr, "%s: no node %s in graph %s in %s\n",
		    CmdName, Nodes[i], agnameof(g), fileName(&ig));
	    code = 1;
	}
	agwrite(g, stdout);
	fflush(stdout);
	agclose(g);
	i++;
    }
    free(Nodes);
    free(Files);
    graphviz_exit(code);
}