#include "../../unity/unity.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>

/* The test file is included into the od translation unit, so it has
   access to the internal functions and globals declared above, such as:
   - static bool read_char (int *c);
   - static bool open_next_file (void);
   - static bool check_and_close (int in_errno);
   - static FILE *in_stream;
   - static char const *const *file_list; */

/* Helper: create a temporary file with the specified content. Returns a
   malloc-allocated string containing the path which the caller must free. */
static char *make_tempfile_with_content(const char *content)
{
    char tmpl[] = "/tmp/od_read_char_test_XXXXXX";
    int fd = mkstemp(tmpl);
    TEST_ASSERT_TRUE_MESSAGE(fd >= 0, "mkstemp failed");

    if (content && content[0] != '\0') {
        size_t len = strlen(content);
        ssize_t wr = write(fd, content, len);
        TEST_ASSERT_EQUAL_INT_MESSAGE((int)len, (int)wr, "write failed");
    }
    close(fd);

    char *path = (char *)malloc(strlen(tmpl) + 1);
    TEST_ASSERT_NOT_NULL(path);
    strcpy(path, tmpl);
    return path;
}

/* Helper: close stream if open and reset pointer. */
static void close_stream_if_open(void)
{
    if (in_stream != NULL) {
        /* Pass 0 so check_and_close checks ferror itself */
        (void)check_and_close(0);
    }
}

void setUp(void) {
    /* Ensure a clean slate before each test */
    close_stream_if_open();
    /* Reset file_list to a benign state (no files). We use a static
       local array here to avoid lifetime issues. */
    static const char *empty_list[] = { NULL };
    file_list = empty_list;
}

void tearDown(void) {
    /* Close any stream that may still be open */
    close_stream_if_open();
}

/* Test: basic single byte read from a file. */
void test_read_char_single_byte(void)
{
    char *p = make_tempfile_with_content("Z");

    const char *flist[] = { p, NULL };
    file_list = flist;

    /* Open first (and only) file via program helper to set globals consistently */
    TEST_ASSERT_TRUE(open_next_file());

    int ch = 0;
    TEST_ASSERT_TRUE(read_char(&ch));
    TEST_ASSERT_EQUAL_INT('Z', ch);

    /* Cleanup */
    close_stream_if_open();
    unlink(p);
    free(p);
}

/* Test: sequential reads across multiple bytes without hitting EOF in read_char. */
void test_read_char_three_bytes(void)
{
    char *p = make_tempfile_with_content("ABC");

    const char *flist[] = { p, NULL };
    file_list = flist;

    TEST_ASSERT_TRUE(open_next_file());

    int ch = 0;
    TEST_ASSERT_TRUE(read_char(&ch));
    TEST_ASSERT_EQUAL_INT('A', ch);
    TEST_ASSERT_TRUE(read_char(&ch));
    TEST_ASSERT_EQUAL_INT('B', ch);
    TEST_ASSERT_TRUE(read_char(&ch));
    TEST_ASSERT_EQUAL_INT('C', ch);

    /* Do not call a 4th time to avoid transitioning to EOF here. */

    close_stream_if_open();
    unlink(p);
    free(p);
}

/* Test: handle EOF on an empty file with no next file. Should return true and set *c = EOF. */
void test_read_char_eof_no_next_file(void)
{
    char *p = make_tempfile_with_content("");

    const char *flist[] = { p, NULL };
    file_list = flist;

    TEST_ASSERT_TRUE(open_next_file());

    int ch = 123; /* init to non-EOF */
    TEST_ASSERT_TRUE(read_char(&ch));
    TEST_ASSERT_EQUAL_INT(EOF, ch);

    /* Subsequent call with in_stream now NULL should also yield EOF and true. */
    ch = 456;
    TEST_ASSERT_TRUE(read_char(&ch));
    TEST_ASSERT_EQUAL_INT(EOF, ch);

    close_stream_if_open();
    unlink(p);
    free(p);
}

/* Test: transition across two files: first has 'A', second has 'B'. */
void test_read_char_transition_to_next_file(void)
{
    char *p1 = make_tempfile_with_content("A");
    char *p2 = make_tempfile_with_content("B");

    const char *flist[] = { p1, p2, NULL };
    file_list = flist;

    TEST_ASSERT_TRUE(open_next_file());

    int ch = 0;
    /* Read from first file */
    TEST_ASSERT_TRUE(read_char(&ch));
    TEST_ASSERT_EQUAL_INT('A', ch);

    /* Next call should hit EOF on first, advance to second, and read 'B' */
    ch = 0;
    TEST_ASSERT_TRUE(read_char(&ch));
    TEST_ASSERT_EQUAL_INT('B', ch);

    /* Third call: both files exhausted -> EOF */
    ch = 0;
    TEST_ASSERT_TRUE(read_char(&ch));
    TEST_ASSERT_EQUAL_INT(EOF, ch);

    close_stream_if_open();
    unlink(p1);
    unlink(p2);
    free(p1);
    free(p2);
}

/* Test: when in_stream is initially NULL (no file opened), read_char should return true and EOF. */
void test_read_char_with_null_stream(void)
{
    /* Ensure no open stream and no files */
    close_stream_if_open();
    static const char *empty_list[] = { NULL };
    file_list = empty_list;

    int ch = 0;
    TEST_ASSERT_TRUE(read_char(&ch));
    TEST_ASSERT_EQUAL_INT(EOF, ch);
}

int main(void)
{
    UNITY_BEGIN();
    RUN_TEST(test_read_char_single_byte);
    RUN_TEST(test_read_char_three_bytes);
    RUN_TEST(test_read_char_eof_no_next_file);
    RUN_TEST(test_read_char_transition_to_next_file);
    RUN_TEST(test_read_char_with_null_stream);
    return UNITY_END();
}