Begin to implement pattern detection

Makefile

@@ -2,11 +2,12 @@
 # Copyright (C) 2022 - Ethan Marshall
 .POSIX:
 
-SRC = xlseq.c
+SRC = xlseq.c patt.c
 OBJ = ${SRC:.c=.o}
 HDR = arg.h
 EXE = xlseq
 
+CFLAGS = -Wall -Wpedantic
 include config.mk
 
 ${EXE}: ${OBJ}

patt.c

@@ -0,0 +1,16 @@
+/* See LICENSE for copyright and license details. */
+
+#include <wchar.h>
+#include <ctype.h>
+
+int
+string_pattern_match(const wchar_t rune)
+{
+	return 1;
+}
+
+int
+number_pattern_match(const wchar_t rune)
+{
+	return isdigit(rune) || rune == '.';
+}

xlseq.c

@@ -1,8 +1,31 @@
 /* See LICENSE for copyright and license details. */
 
 #include <stdio.h>
-#include "arg.h"
 #include <stdlib.h>
+#include <string.h>
+#include <locale.h>
+#include <wchar.h>
+
+#include "xlseq.h"
+#include "arg.h"
+
+#define TRY_MATCH(TYPE, FUNC) if (!out[TYPE-1]) { out[TYPE-1] = !FUNC; }
+
+typedef enum {
+	/* unbounded ranges */
+	StringPattern = 1,	/* common prefix of arbitrary type */
+	NumberPattern,		/* common format of double */
+
+	/* bounded ranges */
+	/* DaysPattern, */
+	/* MonthsPattern, */
+
+	UnrecognisedPattern	/* should never happen;
+				   used to terminate the buffer */
+} PatternType;
+
+struct matcher_state {
+};
 
 char *argv0;
 
@@ -12,9 +35,79 @@ usage()
 	exit(1);
 }
 
+PatternType *
+_type_detect(const char *text)
+{
+	struct matcher_state state;
+	int out[UnrecognisedPattern];
+	PatternType *buf;
+	int used = 0;
+	const char *ptr = text;
+	wchar_t rune;
+	int count, len = strlen(text);
+
+	memset(out, 0, sizeof(out));
+	do {
+		count = mbtowc(&rune, ptr, len-(ptr-text));
+		if (count < 0) {
+			fprintf(stderr, "%s: invalid text encoding\n", argv0);
+			exit(1);
+		}
+		ptr += count;
+
+		TRY_MATCH(StringPattern, string_pattern_match(rune));
+		TRY_MATCH(NumberPattern, number_pattern_match(rune));
+	} while (*ptr);
+
+	buf = malloc(sizeof(out));
+	for (int i = 0; i < UnrecognisedPattern; i++) {
+		if (!out[i]) {
+			buf[used++] = i+1;
+		}
+	}
+
+	return buf;
+}
+
+PatternType
+type_detect(const char *first, const char *second)
+{
+	PatternType *poss, *tmp;
+	PatternType *poss1, *poss2;
+	PatternType max = 0;
+	poss1 = _type_detect(first);
+	poss2 = _type_detect(second);
+
+	/* assumes both buffers are same length */
+	for (poss = poss1; *poss != UnrecognisedPattern; poss++) {
+		if (*poss > max) {
+			for (tmp = poss2; *tmp != UnrecognisedPattern; tmp++) {
+				if (*tmp == *poss) {
+					max = *poss;
+					break;
+				}
+			}
+		}
+	}
+	free(poss1);
+	free(poss2);
+
+	if (!max) {
+		fprintf(stderr, "%s: unrecognised pattern\n", argv0);
+		exit(1);
+	}
+
+	return max;
+}
+
 int
 main(int argc, char **argv)
 {
+	PatternType type = UnrecognisedPattern;
+	int count = -1;
+
+	setlocale(LC_ALL, "");
+
 	ARGBEGIN {
 	case 'u':
 		usage();
@@ -23,4 +116,12 @@ main(int argc, char **argv)
 		fprintf(stderr, "%s: unknown flag '%c'\n", argv0, ARGC());
 		return 1;
 	} ARGEND;
+
+	if (argc < 2) {
+		fprintf(stderr, "%s: need pattern of at least two items\n", argv0);
+		return 1;
+	}
+
+	if (type == UnrecognisedPattern)
+		type = type_detect(argv[argc-2], argv[argc-1]);
 }

xlseq.h

@@ -0,0 +1,7 @@
+/* See LICENSE for copyright and license details. */
+
+/* string pattern */
+int string_pattern_match(const wchar_t rune);
+
+/* number pattern */
+int number_pattern_match(const wchar_t rune);