/*	$Id: docbook2mdoc.c,v 1.9 2014/03/28 13:16:40 kristaps Exp $ */
/*
 * Copyright (c) 2014 Kristaps Dzonsons <kristaps@bsd.lv>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
#include <sys/queue.h>

#include <assert.h>
#include <ctype.h>
#include <expat.h>
#include <fcntl.h>
#include <getopt.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

/*
 * All recognised node types.
 */
enum	nodeid {
	NODE_ROOT = 0, /* Must comes first. */
	/* Alpha-ordered hereafter. */
	NODE_ARG,
	NODE_CITEREFENTRY,
	NODE_CMDSYNOPSIS,
	NODE_CODE,
	NODE_COMMAND,
	NODE_FUNCDEF,
	NODE_FUNCPROTOTYPE,
	NODE_FUNCSYNOPSIS,
	NODE_FUNCSYNOPSISINFO,
	NODE_FUNCTION,
	NODE_MANVOLNUM, 
	NODE_OPTION,
	NODE_PARA,
	NODE_PARAMDEF,
	NODE_PARAMETER,
	NODE_PROGRAMLISTING,
	NODE_REFCLASS,
	NODE_REFDESCRIPTOR,
	NODE_REFENTRY,
	NODE_REFENTRYTITLE,
	NODE_REFMETA,
	NODE_REFMISCINFO,
	NODE_REFNAME,
	NODE_REFNAMEDIV,
	NODE_REFPURPOSE,
	NODE_REFSECT1,
	NODE_REFSYNOPSISDIV,
	NODE_STRUCTNAME,
	NODE_SYNOPSIS,
	NODE_TEXT, 
	NODE_TITLE,
	NODE__MAX
};

/*
 * Global parse state.
 * Keep this as simple and small as possible.
 */
struct	parse {
	enum nodeid	 node; /* current (NODE_ROOT if pre-tree) */
	int		 stop; /* should we stop now? */
	struct pnode	*root; /* root of parse tree */
	struct pnode	*cur; /* current node in tree */
	char		*b; /* nil-terminated buffer for pre-print */
	size_t		 bsz; /* current length of b */
	size_t		 mbsz; /* max bsz allocation */
};

struct	node {
	const char	*name; /* docbook element name */
	unsigned int	 flags;
#define	NODE_IGNTEXT	 1 /* ignore all contained text */
};

TAILQ_HEAD(pnodeq, pnode);

struct	pnode {
	enum nodeid	 node; /* node type */
	char		*b; /* binary data buffer */
	size_t		 bsz; /* data buffer size */
	struct pnode	*parent; /* parent (or NULL if top) */
	struct pnodeq	 childq; /* queue of children */
	TAILQ_ENTRY(pnode) child;
};

static	const struct node nodes[NODE__MAX] = {
	{ NULL, 0 }, 
	{ "arg", 0 }, 
	{ "citerefentry", NODE_IGNTEXT }, 
	{ "cmdsynopsis", NODE_IGNTEXT }, 
	{ "code", 0 }, 
	{ "command", 0 }, 
	{ "funcdef", 0 },
	{ "funcprototype", NODE_IGNTEXT }, 
	{ "funcsynopsis", NODE_IGNTEXT }, 
	{ "funcsynopsisinfo", 0 }, 
	{ "function", 0 }, 
	{ "manvolnum", 0 }, 
	{ "option", 0 }, 
	{ "para", 0 }, 
	{ "paramdef", 0 },
	{ "parameter", 0 }, 
	{ "programlisting", 0 }, 
	{ "refclass", NODE_IGNTEXT }, 
	{ "refdescriptor", NODE_IGNTEXT }, 
	{ "refentry", NODE_IGNTEXT }, 
	{ "refentrytitle", 0 }, 
	{ "refmeta", NODE_IGNTEXT }, 
	{ "refmiscinfo", NODE_IGNTEXT }, 
	{ "refname", 0 }, 
	{ "refnamediv", NODE_IGNTEXT }, 
	{ "refpurpose", 0 }, 
	{ "refsect1", 0 }, 
	{ "refsynopsisdiv", NODE_IGNTEXT }, 
	{ "structname", 0 }, 
	{ "synopsis", 0 }, 
	{ NULL, 0 }, 
	{ "title", 0 }, 
};

/*
 * Look up whether "parent" is a valid parent for "node".
 * This is sucked directly from the DocBook specification: look at the
 * "children" and "parent" sections of each node.
 */
static int
isparent(enum nodeid node, enum nodeid parent)
{

	switch (node) {
	case (NODE_ROOT):
		return(0);
	case (NODE_ARG):
		switch (parent) {
		case (NODE_ARG):
		case (NODE_CMDSYNOPSIS):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_CITEREFENTRY):
		switch (parent) {
		case (NODE_FUNCSYNOPSISINFO):
		case (NODE_PARA):
		case (NODE_PROGRAMLISTING):
		case (NODE_REFDESCRIPTOR):
		case (NODE_REFENTRYTITLE):
		case (NODE_REFNAME):
		case (NODE_REFPURPOSE):
		case (NODE_SYNOPSIS):
		case (NODE_TITLE):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_CMDSYNOPSIS):
		switch (parent) {
		case (NODE_PARA):
		case (NODE_REFSECT1):
		case (NODE_REFSYNOPSISDIV):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_CODE):
		switch (parent) {
		case (NODE_FUNCSYNOPSISINFO):
		case (NODE_PARA):
		case (NODE_PROGRAMLISTING):
		case (NODE_REFDESCRIPTOR):
		case (NODE_REFENTRYTITLE):
		case (NODE_REFNAME):
		case (NODE_REFPURPOSE):
		case (NODE_SYNOPSIS):
		case (NODE_TITLE):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_COMMAND):
		switch (parent) {
		case (NODE_CMDSYNOPSIS):
		case (NODE_FUNCSYNOPSISINFO):
		case (NODE_PARA):
		case (NODE_PROGRAMLISTING):
		case (NODE_REFDESCRIPTOR):
		case (NODE_REFENTRYTITLE):
		case (NODE_REFNAME):
		case (NODE_REFPURPOSE):
		case (NODE_SYNOPSIS):
		case (NODE_TITLE):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_FUNCDEF):
		return(NODE_FUNCPROTOTYPE == parent);
	case (NODE_FUNCPROTOTYPE):
		return(NODE_FUNCSYNOPSIS == parent);
	case (NODE_FUNCSYNOPSIS):
		switch (parent) {
		case (NODE_PARA):
		case (NODE_REFSECT1):
		case (NODE_REFSYNOPSISDIV):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_FUNCSYNOPSISINFO):
		return(NODE_FUNCSYNOPSIS == parent);
	case (NODE_FUNCTION):
		switch (parent) {
		case (NODE_CODE):
		case (NODE_FUNCDEF):
		case (NODE_FUNCSYNOPSISINFO):
		case (NODE_PARA):
		case (NODE_PROGRAMLISTING):
		case (NODE_REFDESCRIPTOR):
		case (NODE_REFENTRYTITLE):
		case (NODE_REFNAME):
		case (NODE_REFPURPOSE):
		case (NODE_SYNOPSIS):
		case (NODE_TITLE):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_MANVOLNUM):
		switch (parent) {
		case (NODE_CITEREFENTRY):
		case (NODE_REFMETA):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_OPTION):
		switch (parent) {
		case (NODE_ARG):
		case (NODE_FUNCSYNOPSISINFO):
		case (NODE_PARA):
		case (NODE_PROGRAMLISTING):
		case (NODE_REFDESCRIPTOR):
		case (NODE_REFENTRYTITLE):
		case (NODE_REFNAME):
		case (NODE_REFPURPOSE):
		case (NODE_SYNOPSIS):
		case (NODE_TITLE):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_PARA):
		switch (parent) {
		case (NODE_REFSECT1):
		case (NODE_REFSYNOPSISDIV):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_PARAMDEF):
		return(NODE_FUNCPROTOTYPE == parent);
	case (NODE_PARAMETER):
		switch (parent) {
		case (NODE_CODE):
		case (NODE_FUNCSYNOPSISINFO):
		case (NODE_PARA):
		case (NODE_PARAMDEF):
		case (NODE_PROGRAMLISTING):
		case (NODE_REFDESCRIPTOR):
		case (NODE_REFENTRYTITLE):
		case (NODE_REFNAME):
		case (NODE_REFPURPOSE):
		case (NODE_SYNOPSIS):
		case (NODE_TITLE):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_PROGRAMLISTING):
		switch (parent) {
		case (NODE_PARA):
		case (NODE_REFSECT1):
		case (NODE_REFSYNOPSISDIV):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_REFCLASS):
		return(parent == NODE_REFNAMEDIV);
	case (NODE_REFDESCRIPTOR):
		return(parent == NODE_REFNAMEDIV);
	case (NODE_REFENTRY):
		return(parent == NODE_ROOT);
	case (NODE_REFENTRYTITLE):
		switch (parent) {
		case (NODE_CITEREFENTRY):
		case (NODE_REFMETA):
			return(1);
		default:
			break;
		}
	case (NODE_REFMETA):
		return(parent == NODE_REFENTRY);
	case (NODE_REFMISCINFO):
		return(parent == NODE_REFMETA);
	case (NODE_REFNAME):
		return(parent == NODE_REFNAMEDIV);
	case (NODE_REFNAMEDIV):
		return(parent == NODE_REFENTRY);
	case (NODE_REFPURPOSE):
		return(parent == NODE_REFNAMEDIV);
	case (NODE_REFSECT1):
		return(parent == NODE_REFENTRY);
	case (NODE_REFSYNOPSISDIV):
		return(parent == NODE_REFENTRY);
	case (NODE_STRUCTNAME):
		switch (parent) {
		case (NODE_CODE):
		case (NODE_FUNCSYNOPSISINFO):
		case (NODE_FUNCTION):
		case (NODE_OPTION):
		case (NODE_PARA):
		case (NODE_PARAMETER):
		case (NODE_PROGRAMLISTING):
		case (NODE_REFDESCRIPTOR):
		case (NODE_REFENTRYTITLE):
		case (NODE_REFNAME):
		case (NODE_REFPURPOSE):
		case (NODE_SYNOPSIS):
		case (NODE_TITLE):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_SYNOPSIS):
		switch (parent) {
		case (NODE_REFSYNOPSISDIV):
		case (NODE_REFSECT1):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_TITLE):
		switch (parent) {
		case (NODE_REFSECT1):
		case (NODE_REFSYNOPSISDIV):
			return(1);
		default:
			break;
		}
		return(0);
	case (NODE_TEXT):
		return(1);
	case (NODE__MAX):
		break;
	}

	abort();
	return(0);
}

/*
 * Process a stream of characters.
 * We store text as nodes in and of themselves.
 * If a text node is already open, append to it.
 * If it's not open, open one under the current context.
 */
static void
xml_char(void *arg, const XML_Char *p, int sz)
{
	struct parse	*ps = arg;
	struct pnode	*dat;
	int		 i;

	/* Stopped or no tree yet. */
	if (ps->stop || NODE_ROOT == ps->node)
		return;

	/* Not supposed to be collecting text. */
	assert(NULL != ps->cur);
	if (NODE_IGNTEXT & nodes[ps->node].flags)
		return;

	/*
	 * Are we in the midst of processing text?
	 * If we're not processing text right now, then create a text
	 * node for doing so.
	 * However, don't do so unless we have some non-whitespace to
	 * process!
	 */
	if (NODE_TEXT != ps->node) {
		for (i = 0; i < sz; i++)
			if ( ! isspace((int)p[i]))
				break;
		if (i == sz)
			return;
		dat = calloc(1, sizeof(struct pnode));
		if (NULL == dat) {
			perror(NULL);
			exit(EXIT_FAILURE);
		}

		dat->node = ps->node = NODE_TEXT;
		dat->parent = ps->cur;
		TAILQ_INIT(&dat->childq);
		TAILQ_INSERT_TAIL(&ps->cur->childq, dat, child);
		ps->cur = dat;
		assert(NULL != ps->root);

	}

	/* Append to current buffer. */
	assert(sz >= 0);
	ps->cur->b = realloc(ps->cur->b, 
		ps->cur->bsz + (size_t)sz);
	if (NULL == ps->cur->b) {
		perror(NULL);
		exit(EXIT_FAILURE);
	}
	memcpy(ps->cur->b + ps->cur->bsz, p, sz);
	ps->cur->bsz += (size_t)sz;
}

/*
 * Begin an element.
 * First, look for the element.
 * If we don't find it and we're not parsing, keep going.
 * If we don't find it and we're parsing, puke and exit.
 * If we find it but we're not parsing yet (i.e., it's not a refentry
 * and thus out of context), keep going.
 * If we find it and we're at the root and already have a tree, puke and
 * exit (FIXME: I don't think this is right?).
 * If we find it but we're parsing a text node, close out the text node,
 * return to its parent, and keep going.
 * Make sure that the element is in the right context.
 * Lastly, put the node onto our parse tree and continue.
 */
static void
xml_elem_start(void *arg, const XML_Char *name, const XML_Char **atts)
{
	struct parse	*ps = arg;
	enum nodeid	 node;
	struct pnode	*dat;

	if (ps->stop)
		return;

	/* Close out text node, if applicable... */
	if (NODE_TEXT == ps->node) {
		assert(NULL != ps->cur);
		ps->cur = ps->cur->parent;
		assert(NULL != ps->cur);
		ps->node = ps->cur->node;
	}

	for (node = 0; node < NODE__MAX; node++)
		if (NULL == nodes[node].name)
			continue;
		else if (0 == strcmp(nodes[node].name, name))
			break;

	/* FIXME: do more with these error messages... */
	if (NODE__MAX == node && NODE_ROOT == ps->node) {
		fprintf(stderr, "%s: ignoring node\n", name);
		return;
	} else if (NODE__MAX == node) {
		fprintf(stderr, "%s: unknown node\n", name);
		ps->stop = 1;
		return;
	} else if (NODE_ROOT == ps->node && NULL != ps->root) {
		fprintf(stderr, "%s: reentering?\n", name);
		ps->stop = 1;
		return;
	} else if (NODE_ROOT == ps->node && NODE_REFENTRY != node) {
		fprintf(stderr, "%s: known node w/o context\n", name);
		return;
	} else if ( ! isparent(node, ps->node)) {
		fprintf(stderr, "%s: bad parent\n", name);
		ps->stop = 1;
		return;
	}

	if (NULL == (dat = calloc(1, sizeof(struct pnode)))) {
		perror(NULL);
		exit(EXIT_FAILURE);
	}

	dat->node = ps->node = node;
	dat->parent = ps->cur;
	TAILQ_INIT(&dat->childq);

	if (NULL != ps->cur)
		TAILQ_INSERT_TAIL(&ps->cur->childq, dat, child);

	ps->cur = dat;
	if (NULL == ps->root)
		ps->root = dat;
}

/*
 * Roll up the parse tree.
 * If we're at a text node, roll that one up first.
 * If we hit the root, then assign ourselves as the NODE_ROOT.
 */
static void
xml_elem_end(void *arg, const XML_Char *name)
{
	struct parse	*ps = arg;

	if (ps->stop || NODE_ROOT == ps->node)
		return;

	/* Close out text node, if applicable... */
	if (NODE_TEXT == ps->node) {
		assert(NULL != ps->cur);
		ps->cur = ps->cur->parent;
		assert(NULL != ps->cur);
		ps->node = ps->cur->node;
	}

	if (NULL == (ps->cur = ps->cur->parent))
		ps->node = NODE_ROOT;
	else
		ps->node = ps->cur->node;
}

/*
 * Recursively free a node (NULL is ok).
 */
static void
pnode_free(struct pnode *pn)
{
	struct pnode	*pp;

	if (NULL == pn)
		return;

	while (NULL != (pp = TAILQ_FIRST(&pn->childq))) {
		TAILQ_REMOVE(&pn->childq, pp, child);
		pnode_free(pp);
	}

	free(pn->b);
	free(pn);
}

/*
 * Unlink a node from its parent and pnode_free() it.
 */
static void
pnode_unlink(struct pnode *pn)
{

	if (NULL != pn->parent)
		TAILQ_REMOVE(&pn->parent->childq, pn, child);
	pnode_free(pn);
}

/*
 * Unlink all children of a node and pnode_free() them.
 */
static void
pnode_unlinksub(struct pnode *pn)
{

	while ( ! TAILQ_EMPTY(&pn->childq))
		pnode_unlink(TAILQ_FIRST(&pn->childq));
}

/*
 * Reset the lookaside buffer.
 */
static void
bufclear(struct parse *p)
{

	p->b[p->bsz = 0] = '\0';
}

/*
 * Append NODE_TEXT contents to the current buffer, reallocating its
 * size if necessary.
 * The buffer is ALWAYS nil-terminated.
 */
static void
bufappend(struct parse *p, struct pnode *pn)
{

	assert(NODE_TEXT == pn->node);
	if (p->bsz + pn->bsz + 1 > p->mbsz) {
		p->mbsz = p->bsz + pn->bsz + 1;
		if (NULL == (p->b = realloc(p->b, p->mbsz))) {
			perror(NULL);
			exit(EXIT_FAILURE);
		}
	}
	memcpy(p->b + p->bsz, pn->b, pn->bsz);
	p->bsz += pn->bsz;
	p->b[p->bsz] = '\0';
}

/*
 * Recursively append all NODE_TEXT nodes to the buffer.
 * This descends into non-text nodes, but doesn't do anything beyond
 * them.
 * In other words, this is a recursive text grok.
 */
static void
bufappend_r(struct parse *p, struct pnode *pn)
{
	struct pnode	*pp;

	if (NODE_TEXT == pn->node)
		bufappend(p, pn);
	TAILQ_FOREACH(pp, &pn->childq, child)
		bufappend_r(p, pp);
}

/*
 * Recursively print text presumably on a macro line.
 * Convert all whitespace to regular spaces.
 */
static void
pnode_printmacrolinepart(struct parse *p, struct pnode *pn)
{
	char		*cp;

	bufclear(p);
	bufappend_r(p, pn);

	/* Convert all space to spaces. */
	for (cp = p->b; '\0' != *cp; cp++)
		if (isspace((int)*cp))
			*cp = ' ';

	for (cp = p->b; isspace((int)*cp); cp++)
		/* Spin past whitespace (XXX: necessary?) */ ;
	for ( ; '\0' != *cp; cp++) {
		/* Escape us if we look like a macro. */
		if ((cp == p->b || ' ' == *(cp - 1)) &&
			isupper((int)*cp) &&
			'\0' != *(cp + 1) && 
			islower((int)*(cp + 1)) &&
			('\0' == *(cp + 2) || 
			 ' ' == *(cp + 2) ||
			 (islower((int)*(cp + 2)) &&
			  ('\0' == *(cp + 3) || 
			   ' ' == *(cp + 3)))))
			fputs("\\&", stdout);
		putchar(*cp);
		/* If we're a character escape, escape us. */
		if ('\\' == *cp)
			putchar('e');
	}
}

/*
 * Just pnode_printmacrolinepart() but with a newline.
 * If no text, just the newline.
 */
static void
pnode_printmacroline(struct parse *p, struct pnode *pn)
{

	pnode_printmacrolinepart(p, pn);
	putchar('\n');
}

/*
 * Start the SYNOPSIS macro, unlinking its [superfluous] title.
 */
static void
pnode_printrefsynopsisdiv(struct parse *p, struct pnode *pn)
{
	struct pnode	*pp;

	TAILQ_FOREACH(pp, &pn->childq, child)
		if (NODE_TITLE == pp->node) {
			pnode_unlink(pp);
			break;
		}

	puts(".Sh SYNOPSIS");
}

/*
 * Start a hopefully-named `Sh' section.
 */
static void
pnode_printrefsect(struct parse *p, struct pnode *pn)
{
	struct pnode	*pp;

	TAILQ_FOREACH(pp, &pn->childq, child)
		if (NODE_TITLE == pp->node)
			break;

	fputs(".Sh ", stdout);

	if (NULL != pp) {
		pnode_printmacroline(p, pp);
		pnode_unlink(pp);
	} else
		puts("UNKNOWN");
}

/*
 * Start a reference, extracting the title and volume.
 */
static void
pnode_printciterefentry(struct parse *p, struct pnode *pn)
{
	struct pnode	*pp, *title, *manvol;

	title = manvol = NULL;
	TAILQ_FOREACH(pp, &pn->childq, child)
		if (NODE_MANVOLNUM == pp->node)
			manvol = pp;
		else if (NODE_REFENTRYTITLE == pp->node)
			title = pp;

	fputs(".Xr ", stdout);

	if (NULL != title) {
		pnode_printmacrolinepart(p, title);
		putchar(' ');
	} else
		fputs("unknown ", stdout);

	if (NULL != manvol)
		pnode_printmacroline(p, manvol);
	else
		puts("1");
}

static void
pnode_printrefmeta(struct parse *p, struct pnode *pn)
{
	struct pnode	*pp, *title, *manvol;

	title = manvol = NULL;
	TAILQ_FOREACH(pp, &pn->childq, child)
		if (NODE_MANVOLNUM == pp->node)
			manvol = pp;
		else if (NODE_REFENTRYTITLE == pp->node)
			title = pp;

	puts(".Dd $Mdocdate" "$");
	fputs(".Dt ", stdout);

	if (NULL != title) {
		/* FIXME: uppercase. */
		pnode_printmacrolinepart(p, title);
		putchar(' ');
	} else
		fputs("UNKNOWN ", stdout);

	if (NULL != manvol)
		pnode_printmacroline(p, manvol);
	else
		puts("1");

	puts(".Os");
}

static void
pnode_printfuncdef(struct parse *p, struct pnode *pn)
{
	struct pnode	*pp, *ftype, *func;

	ftype = func = NULL;
	TAILQ_FOREACH(pp, &pn->childq, child)
		if (NODE_TEXT == pp->node)
			ftype = pp;
		else if (NODE_FUNCTION == pp->node)
			func = pp;

	if (NULL != ftype) {
		fputs(".Ft ", stdout);
		pnode_printmacroline(p, ftype);
	}

	if (NULL != func) {
		fputs(".Fo ", stdout);
		pnode_printmacroline(p, func);
	} else 
		puts(".Fo UNKNOWN");
}

static void
pnode_printparamdef(struct parse *p, struct pnode *pn)
{
	struct pnode	*pp, *ptype, *param;

	ptype = param = NULL;
	TAILQ_FOREACH(pp, &pn->childq, child)
		if (NODE_TEXT == pp->node)
			ptype = pp;
		else if (NODE_PARAMETER == pp->node)
			param = pp;

	fputs(".Fa \"", stdout);
	if (NULL != ptype) {
		pnode_printmacrolinepart(p, ptype);
		putchar(' ');
	}

	if (NULL != param)
		pnode_printmacrolinepart(p, param);
	else
		fputs("UNKNOWN", stdout);

	puts("\"");
}

static void
pnode_printfuncprototype(struct parse *p, struct pnode *pn)
{
	struct pnode	*pp, *fdef;

	TAILQ_FOREACH(fdef, &pn->childq, child)
		if (NODE_FUNCDEF == fdef->node) 
			break;

	if (NULL != fdef)
		pnode_printfuncdef(p, fdef);
	else
		puts(".Fo UNKNOWN");

	TAILQ_FOREACH(pp, &pn->childq, child) 
		if (NODE_PARAMDEF == pp->node)
			pnode_printparamdef(p, pp);

	puts(".Fc");
}

/* TODO: handle "optional" values. */
static void
pnode_printarg(struct parse *p, struct pnode *pn, int nested)
{
	struct pnode	*pp;
	int		 sv = nested;

	if ( ! nested) 
		fputs(".", stdout);
	nested = 1;
	TAILQ_FOREACH(pp, &pn->childq, child)
		if (NODE_OPTION == pp->node) {
			fputs("Fl ", stdout);
			pnode_printmacrolinepart(p, pp);
		} else if (NODE_TEXT == pp->node) {
			fputs("Ar ", stdout);
			pnode_printmacrolinepart(p, pp);
		} else if (NODE_ARG == pp->node)
			pnode_printarg(p, pp, nested);

	if ( ! sv)
		puts("");
}

/* 
 * Recursively search and return the first instance of "node".
 */
static struct pnode *
pnode_findfirst(struct pnode *pn, enum nodeid node)
{
	struct pnode	*pp, *res;

	res = NULL;
	TAILQ_FOREACH(pp, &pn->childq, child) {
		res = pp->node == node ? pp :
			pnode_findfirst(pp, node);
		if (NULL != res)
			break;
	}

	return(res);
}

static void
pnode_printprologue(struct parse *p, struct pnode *pn)
{
	struct pnode	*pp;

	pp = NULL == p->root ? NULL :
		pnode_findfirst(p->root, NODE_REFMETA);

	if (NULL != pp) {
		pnode_printrefmeta(p, pp);
		pnode_unlink(pp);
	} else {
		puts(".\\\" Supplying bogus prologue...");
		puts(".Dd $Mdocdate" "$");
		puts(".Dt UNKNOWN 1");
		puts(".Os");
	}
}

/*
 * Print a parsed node (or ignore it--whatever).
 * This is a recursive function.
 * FIXME: macro line continuation?
 */
static void
pnode_print(struct parse *p, struct pnode *pn)
{
	struct pnode	*pp;
	char		*cp;
	int		 last;

	if (NULL == pn)
		return;

	if (NODE_TEXT != pn->node && NODE_ROOT != pn->node)
		printf(".\\\" %s\n", nodes[pn->node].name);

	switch (pn->node) {
	case (NODE_ARG):
		pnode_printarg(p, pn, 0);
		pnode_unlinksub(pn);
		break;
	case (NODE_CITEREFENTRY):
		pnode_printciterefentry(p, pn);
		pnode_unlinksub(pn);
		break;
	case (NODE_CODE):
		fputs(".Li ", stdout);
		pnode_printmacroline(p, pn);
		pnode_unlinksub(pn);
		break;
	case (NODE_COMMAND):
		fputs(".Nm ", stdout);
		pnode_printmacroline(p, pn);
		pnode_unlinksub(pn);
		break;
	case (NODE_FUNCTION):
		fputs(".Fn ", stdout);
		pnode_printmacroline(p, pn);
		pnode_unlinksub(pn);
		break;
	case (NODE_FUNCPROTOTYPE):
		pnode_printfuncprototype(p, pn);
		pnode_unlinksub(pn);
		break;
	case (NODE_FUNCSYNOPSISINFO):
		fputs(".Fd ", stdout);
		pnode_printmacroline(p, pn);
		pnode_unlinksub(pn);
		break;
	case (NODE_PARA):
		/* FIXME: not always. */
		puts(".Pp");
		break;
	case (NODE_PARAMETER):
		fputs(".Fa \"", stdout);
		pnode_printmacrolinepart(p, pn);
		puts("\"");
		pnode_unlinksub(pn);
		break;
	case (NODE_PROGRAMLISTING):
		puts(".Bd -literal");
		break;
	case (NODE_REFMETA):
		abort();
		break;
	case (NODE_REFNAME):
		fputs(".Nm ", stdout);
		pnode_printmacroline(p, pn);
		pnode_unlinksub(pn);
		return;
	case (NODE_REFNAMEDIV):
		puts(".Sh NAME");
		break;
	case (NODE_REFPURPOSE):
		fputs(".Nd ", stdout);
		pnode_printmacroline(p, pn);
		pnode_unlinksub(pn);
		return;
	case (NODE_REFSYNOPSISDIV):
		pnode_printrefsynopsisdiv(p, pn);
		break;
	case (NODE_REFSECT1):
		pnode_printrefsect(p, pn);
		break;
	case (NODE_STRUCTNAME):
		fputs(".Vt ", stdout);
		pnode_printmacroline(p, pn);
		pnode_unlinksub(pn);
		return;
	case (NODE_TEXT):
		bufclear(p);
		bufappend(p, pn);
		/*
		 * Output all characters, squeezing out whitespace
		 * between newlines. 
		 * XXX: all whitespace, including tabs (?).
		 * Remember to escape control characters and escapes.
		 */
		for (last = '\n', cp = p->b; '\0' != *cp; ) {
			if ('\n' == last) {
				/* Consume all whitespace. */
				if (isspace((int)*cp)) {
					while (isspace((int)*cp))
						cp++;
					continue;
				} else if ('\'' == *cp || '.' == *cp)
					fputs("\\&", stdout);
			}
			putchar(last = *cp++);
			/* If we're a character escape, escape us. */
			if ('\\' == last)
				putchar('e');
		}
		if ('\n' != last)
			putchar('\n');
		break;
	default:
		break;
	}

	TAILQ_FOREACH(pp, &pn->childq, child)
		pnode_print(p, pp);

	switch (pn->node) {
	case (NODE_PROGRAMLISTING):
		puts(".Ed");
		break;
	default:
		break;
	}
}

/*
 * Loop around the read buffer until we've drained it of all data.
 * Invoke the parser context with each buffer fill.
 */
static int
readfile(XML_Parser xp, int fd, 
	char *b, size_t bsz, const char *fn)
{
	struct parse	 p;
	int		 rc;
	ssize_t		 ssz;

	memset(&p, 0, sizeof(struct parse));

	p.b = malloc(p.bsz = p.mbsz = 1024);

	XML_SetCharacterDataHandler(xp, xml_char);
	XML_SetElementHandler(xp, xml_elem_start, xml_elem_end);
	XML_SetUserData(xp, &p);

	while ((ssz = read(fd, b, bsz)) >= 0) {
		if (0 == (rc = XML_Parse(xp, b, ssz, 0 == ssz)))
			fprintf(stderr, "%s: %s\n", fn,
				XML_ErrorString
				(XML_GetErrorCode(xp)));
		else if ( ! p.stop && ssz > 0)
			continue;
		/* 
		 * Exit when we've read all or errors have occured
		 * during the parse sequence.
		 */
		pnode_printprologue(&p, p.root);
		pnode_print(&p, p.root);
		pnode_free(p.root);
		free(p.b);
		return(0 != rc && ! p.stop);
	}

	/* Read error has occured. */
	perror(fn);
	pnode_free(p.root);
	free(p.b);
	return(0);
}

int
main(int argc, char *argv[])
{
	XML_Parser	 xp;
	const char	*fname;
	char		*buf;
	int		 fd, rc;

	fname = "-";
	xp = NULL;
	buf = NULL;
	rc = 0;

	if (-1 != getopt(argc, argv, ""))
		return(EXIT_FAILURE);

	argc -= optind;
	argv += optind;

	if (argc > 1)
		return(EXIT_FAILURE);
	else if (argc > 0)
		fname = argv[0];

	/* Read from stdin or a file. */
	fd = 0 == strcmp(fname, "-") ? 
		STDIN_FILENO : open(fname, O_RDONLY, 0);

	/*
	 * Open file for reading.
	 * Allocate a read buffer.
	 * Create the parser context.
	 * Dive directly into the parse.
	 */
	if (-1 == fd)
		perror(fname);
	else if (NULL == (buf = malloc(4096)))
		perror(NULL);
	else if (NULL == (xp = XML_ParserCreate(NULL)))
		perror(NULL);
	else if ( ! readfile(xp, fd, buf, 4096, fname))
		rc = 1;

	XML_ParserFree(xp);
	free(buf);
	if (STDIN_FILENO != fd)
		close(fd);
	return(rc ? EXIT_SUCCESS : EXIT_FAILURE);
}