use stdlib.h
use stdio.h
use ctype.h
use string.h

enum { MAXLINE = 4096 }
char buf[MAXLINE]

enum { MAXTABS = 256 }
enum { SWITCH, WHICH, STRUCT, CLASS, INIT, VOID_MAIN, MACRO, DO, DOWHILE, ELSE, OTHER }

char *kwdparens[] = { "if", "else if", "while", "do", "for", "switch", "else", 0 }

char *line
int len
int tabs
int lasttabs
int skipsemi
char *label
char *lastlabel = 0
# XXX do lastlabel and lastcase work?
# isn't the buffer overwritten for each line?
int lastblank
char *caselabel
char *lastcase = 0
int casetabs
int in_macro = 0
int first_line_of_macro = 0

int blocktype[MAXTABS]
int is_kwdparens
int is_static

# begins_with is from b/text.b
# TODO: use that library (with BRACE_STANDALONE)
# this returns a pointer to the character after the match, or NULL
char *cstr_begins_with(char *s, const char *substr)
	repeat
		if *substr == '\0'
			return s
		if *substr != *s
			return NULL
		++s ; ++substr

exits(char *msg)
	if msg == NULL
		exit(0)
	else
		fprintf(stderr, "%s\n", msg)
		exit(1)

writes(char *str)
	printf("%s", str)

char last()
	if len == 0
		return '\0'
	return line[len-1]

int readln()
	line = fgets(buf, MAXLINE, stdin)
	if line == NULL
		return 0
	len = strlen(line)
	if last() != '\n' && last() != '\r'
		exits("line too long or does not end with newline")
	while last() == '\n' || last() == '\r'
		line[--len] = '\0'
	return 1

int striptabs()
	int tabs = 0
	while line[0] == '\t'
		++line
		++tabs
		--len
	return tabs

fussy()
	if line[0] == ' '
		exits("two spaces at start of line")
	if last() == ' '
		exits("space at end of line")

int wordlen()
	return strspn(line, "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_0123456789.")

int caselen()
	return strcspn(line, "\t")

strip_one_space_maybe()
	if line[0] == ' '
		++line
		--len

int readstmt()
	if !readln()
		tabs = 0
		return 0
	tabs = striptabs()
	strip_one_space_maybe()
	fussy()
	
	label = 0
	if len > 0 && tabs == 0
		int lbllen = wordlen()
		if line[lbllen] == '\t'
			label = line
			line += lbllen
			len -= lbllen
			tabs = striptabs()
			label[lbllen] = '\0'
	
	caselabel = 0
	casetabs = 0
	if len > 0 && tabs > 0 && line[0] != '#'
		int lbllen = caselen()
		if line[lbllen] == ',' && line[lbllen+1] == '\t'
			line[lbllen] = '\0'
			lbllen++
		if line[lbllen] == '\t'
			caselabel = line
			line += lbllen
			len -= lbllen
			casetabs = striptabs()
			caselabel[lbllen] = '\0'
			tabs += casetabs
	
	if len == 1 && line[0] == '.'
		line[0] = '\0' ; len = 0
	
	if tabs >= MAXTABS
		exits("too many tabs")
	
	return 1

indent(int tabs)
	for ; tabs>0; --tabs
		writes("\t")

addvoids()
	char *c1 = cstr_begins_with(line, "extern \"C\" ")
	if c1
		writes("extern \"C\" ")
		line = c1
	int addvoid = 1
	char *c = line
	for ; *c != 0; ++c
		if *c == ' '
			addvoid = 0
		if *c == '('
			if addvoid
				if cstr_begins_with(line, "main(")
					writes("int ")
					blocktype[tabs] = VOID_MAIN
				else
					writes("void ")
			if c[1] == ')'
				c[1] = '\0'
				writes(line)
				c[1] = ')'
				writes("void")
				len -= (c - line) + 1
				line = c + 1
			break

procstmt()
	char **k
	char *c
	if (c = cstr_begins_with(line, "which "))
		writes("switch(")
		writes(c)
		line = ")" ; len = 1
	eif cstr_begins_with(line, "eif ")
		writes("else if(")
		writes(line+4)
		line = ")" ; len = 1
		is_kwdparens = 1
	eif strcmp(line, "repeat") == 0
		line = "while(1)" ; len = 8
	#eif strcmp(line, "stop") == 0
	#	line = "break" ; len = 5
	else
		for k=kwdparens; *k != 0; ++k
			int l = strlen(*k)
			if cstr_begins_with(line, *k) && (line[l] == ' ' || line[l] == '\0')
				if line[l] == ' '
					line[l] = '('
					writes(line)
					line = ")" ; len = 1
				is_kwdparens = 1
				break

int classy(char *c)
	char *spc = strchr(c, ' ')
	char *colon = strchr(c, ':')
	char *paren = strchr(c, '(')
	return !paren && (!spc || colon == spc + 1 || colon < spc)

writestmt()
	is_kwdparens = 0
	is_static = 0

	if caselabel && lasttabs >= tabs && !(lastblank && lastcase) \
			&& blocktype[tabs-1] == WHICH
		indent(tabs)
		writes("break;\n")
	
	if label
		if isdigit((int)label[0])
			writes("_")
		writes(label)
		writes(":")
	
	indent(tabs - casetabs)
	
	if caselabel
		if caselabel[0] == '\0'
			exits("spurious space between tabs")
		eif strcmp(caselabel, "else") == 0
			writes("default:")
		else
			writes("case ")
			writes(caselabel)
			writes(":")
		indent(casetabs)

	if strcmp(line, "do") == 0
		blocktype[tabs] = DO
	eif blocktype[tabs] == DO && cstr_begins_with(line, "while ")
		blocktype[tabs] = DOWHILE
	eif cstr_begins_with(line, "switch ")
		blocktype[tabs] = SWITCH
	eif cstr_begins_with(line, "else") && (len == 4 || line[4] == ' ')
		blocktype[tabs] = ELSE
	eif cstr_begins_with(line, "which ")
		blocktype[tabs] = WHICH
	eif (cstr_begins_with(line, "enum") && (len == 4 || line[4] == ' ')) || \
			line[len-1] == '=' || \
			(tabs > 0 && blocktype[tabs-1] == INIT)
		blocktype[tabs] = INIT
	eif tabs > lasttabs && blocktype[lasttabs] == INIT
		int i
		for i=lasttabs+1; i<=tabs; ++i
			blocktype[i] = INIT
	else
		# check for struct, union, class
		char *c = line
		if cstr_begins_with(c, "template<")
			c = strchr(c+9, '>')
			if c == NULL
				exits("template is missing >")
			++c
			if *c == '\0'
				exits("template<...> must be followed by the start of a declaration on the same line")
			if *c != ' '
				exits("template<...> must be followed by a space")
			++c
		 eif cstr_begins_with(c, "extern \"C\" ")
			c += 11
			if *c == '\0'
				exits("extern \"C\" must be followed by the start of a declaration on the same line")
		
		if cstr_begins_with(c, "struct ") && classy(c+7)
			blocktype[tabs] = STRUCT
		eif cstr_begins_with(c, "union ") && classy(c+6)
			blocktype[tabs] = STRUCT
		eif cstr_begins_with(c, "class ") && classy(c+6)
			blocktype[tabs] = CLASS
		eif *c == '^' || *c == '#'
			# ignore directives and comments, not indented properly
		else
			blocktype[tabs] = OTHER
		# to be continued?
	
	skipsemi = 0
	if len > 0 && line[wordlen()] == '\0' && tabs > 0 && \
			blocktype[tabs] != INIT && \
				strcmp(line, "else") != 0 && \
				strcmp(line, "return") != 0 && \
				strcmp(line, "break") != 0 && \
				strcmp(line, "continue") != 0 && \
				strcmp(line, "do") != 0 && \
				strcmp(line, "repeat") != 0
			writes("goto ")
			if isdigit((int)line[0])
				writes("_")
	eif line[0] == '#'
		writes("/")
		line[0] = '/'
	eif cstr_begins_with(line, "export ") || cstr_begins_with(line, "use ")
		line = strchr(line, ' ') + 1
		writes("#include ")
		writes(line)
		line = "" ; len = 0
	eif cstr_begins_with(line, "def ")
		if tabs != 0
			exits("macro definitions must be at top level")
		blocktype[tabs] = MACRO
		in_macro = 1
		first_line_of_macro = 1
		writes("#define ")
		line += 4 ; len -= 4
	eif cstr_begins_with(line, "local ") || cstr_begins_with(line, "static ")
		char *l = strchr(line, ' ')+1
		writes("static ")
		is_static = 1
		len -= (l-line) ; line = l
		if tabs == 0
			addvoids()
	eif cstr_begins_with(line, "^")
		writes("#")
		skipsemi = 1
		line++ ; len--
	eif line[len-1] == '{' || strcmp(line, "}") == 0
		skipsemi = 1
	eif tabs == 0
		addvoids()
	else
		procstmt()
	
	writes(line)
	
	skipsemi = skipsemi || len == 0 || line[0] == '"' || line[0] == '<' || \
		line[0] == '/' || last() == '/'
	
	if caselabel && len == 0
		skipsemi = 0
	
	lastblank = len == 0
	lastlabel = 0
	lastcase = 0
	if label || !lastblank
		lastlabel = label
	if caselabel && !lastblank
		lastcase = caselabel
	lasttabs = tabs

writedelim()
	int lt = lasttabs
	if first_line_of_macro
		skipsemi = 1
		if tabs != 0
			lt = tabs
	if lt >= tabs && \
			(!skipsemi || \
				(lastblank && (lastlabel || lastcase))) && \
			!(lt > 0 && blocktype[lt-1] == INIT)
		if is_kwdparens && blocktype[lt] != DOWHILE
			writes(" {}")
		 else
			writes(";")
	if in_macro && tabs > 0
		writes(" \\")
	writes("\n")
	if !(in_macro && tabs == 0)
		while lt > tabs
			indent(--lt)
			if blocktype[lt] == STRUCT || blocktype[lt] == CLASS
				writes("};\n")
			eif blocktype[lt] == INIT && !(lt>0 && blocktype[lt-1] == INIT)
				writes("};\n")
			else
				if lt == 0 && blocktype[0] == VOID_MAIN
					writes("\treturn 0;\n")
				writes("}\n")
		while lt < tabs
			indent(lt++)
			writes("{\n")
	if in_macro && tabs == 0
		in_macro = 0
	first_line_of_macro = 0

int main()
	writes("// brace: this C file was generated from brace source code; read that instead\n\n")
	if readstmt()
		writestmt()
		while readstmt()
			writedelim()
			writestmt()
		writedelim()
	return 0