Extract line reading logic to reader and remove REPL tests

Reading a line into the buffer was the only logic complex enough to be
worth testing really, and exposing the necessary parts of it to test
it effectively was a pain.  Makes more sense to move read_line out and
throw away most of the tests.

lib/include/reader.h

@@ -3,6 +3,8 @@
 
 #include "memory_pool.h"
 
+int read_line(int (*get_byte)(void), char *buffer, int buffer_size);
+
 const expression_t *
 read_expression(memory_pool_t *pool, const char *input, int len);
 

lib/include/repl.h

@@ -3,23 +3,11 @@
 
 #include "memory_pool.h"
 
-#define REPL_LINE_BUFFER_SIZE 128
-#define REPL_RESULT_BUFFER_SIZE 128
-
-typedef int (*get_byte_fn_t)(void);
-typedef const expression_t *(*read_fn_t)(
-    memory_pool_t *pool, const char *input, int len);
-typedef int (*evaluate_fn_t)(const expression_t *expression);
-typedef void (*print_fn_t)(const char *output, int len);
+#define REPL_BUFFER_SIZE 128
 
 typedef struct {
-	get_byte_fn_t get_byte;
-	read_fn_t read;
-	evaluate_fn_t evaluate;
-	print_fn_t print;
 	memory_pool_t pool;
-	char line_buffer[REPL_LINE_BUFFER_SIZE];
-	char result_buffer[REPL_RESULT_BUFFER_SIZE];
+	char buffer[REPL_BUFFER_SIZE];
 } repl_t;
 
 bool step_repl(repl_t *repl);

lib/reader.c

@@ -2,6 +2,7 @@
 
 #include <ctype.h>
 #include <stddef.h>
+#include <stdio.h>
 
 static int parse_expression(
     memory_pool_t *pool, const char *input, int len, expression_t **out);
@@ -152,6 +153,19 @@ static int parse_expression(
 	return used;
 }
 
+int read_line(int (*get_byte)(void), char *buffer, int buffer_size)
+{
+	for (int len = 0; len < buffer_size; ++len) {
+		const int byte = get_byte();
+		if (EOF == byte)
+			return -1;
+		if ('\n' == byte)
+			return len;
+		buffer[len] = (char)byte;
+	}
+	return buffer_size;
+}
+
 const expression_t *
 read_expression(memory_pool_t *pool, const char *input, int len)
 {

lib/repl.c

@@ -1,5 +1,8 @@
 #include "repl.h"
 
+#include "evaluator.h"
+#include "reader.h"
+
 #include <stdio.h>
 #include <string.h>
 
@@ -7,26 +10,17 @@ bool step_repl(repl_t *repl)
 {
 	init_memory_pool(&repl->pool);
 
-	int len;
-	for (len = 0; len < REPL_LINE_BUFFER_SIZE; ++len) {
-		const int byte = repl->get_byte();
-		if (EOF == byte)
-			return false;
-		else if ('\n' == byte)
-			break;
-		repl->line_buffer[len] = (char)byte;
-	}
-	const expression_t *e = repl->read(&repl->pool, repl->line_buffer, len);
+	const int len = read_line(getchar, repl->buffer, REPL_BUFFER_SIZE);
+	if (len < 0)
+		return false;
+	const expression_t *e = read_expression(&repl->pool, repl->buffer, len);
 	if (NULL == e) {
-		const char *msg = "Invalid expression\n";
-		repl->print(msg, strlen(msg));
+		puts("Invalid expression\n");
 		return true;
 	}
 
-	const int result = repl->evaluate(e);
-	const int result_len = snprintf(
-	    repl->result_buffer, REPL_RESULT_BUFFER_SIZE, "%d\n", result);
-	repl->print(repl->result_buffer, result_len);
+	const int result = evaluate(e);
+	printf("%d\n", result);
 
 	return true;
 }