#include "buffer.h"

#include <stdlib.h>
#include <stdio.h>

typedef enum {
	BUFFER_FILE,
	BUFFER_STRING
} BufferType;

struct Buffer {
	BufferType type;
	union {
		FILE* file;
		struct {
			const char* data;
			size_t pos;
		} string;
	} source;
};

Buffer* buffer_open_file(const char* path) {
	FILE* f = fopen(path, "r");
	if (f == NULL)
		return NULL;
	Buffer* buf = malloc(sizeof(Buffer));
	if (buf == NULL) {
		fclose(f);
		return NULL;
	}
	buf->type = BUFFER_FILE;
	buf->source.file = f;
	return buf;
}

Buffer* buffer_open_string(const char* string) {
	Buffer* buf = malloc(sizeof(Buffer));
	if (buf == NULL)
		return NULL;
	buf->type = BUFFER_STRING;
	buf->source.string.data = string;
	buf->source.string.pos = 0;
	return buf;
}

void buffer_close(Buffer* buffer) {
	if (buffer->type == BUFFER_FILE)
		fclose(buffer->source.file);
	free(buffer);
}

char buffer_read(Buffer* buffer) {
	if (buffer->type == BUFFER_FILE) {
		int c = fgetc(buffer->source.file);
		return c == EOF ? (char)-1 : (char)c;
	} else {
		char c = buffer->source.string.data[buffer->source.string.pos];
		if (c == '\0')
			return (char)-1;
		buffer->source.string.pos++;
		return c;
	}
}