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

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

/* Helper: run expand() with given input string.
   If initial_only is true, simulate -i by setting convert_entire_line = false.
   Returns a newly malloc'd string with the captured output, or NULL on error. */
static char* run_expand_on_input(const char* input, bool initial_only)
{
    int saved_stdin = -1;
    int saved_stdout = -1;
    FILE* in_file = NULL;
    FILE* out_file = NULL;
    int in_fd, out_fd;
    char* out_buf = NULL;

    /* Create temp files for input and output */
    in_file = tmpfile();
    if (!in_file) goto fail;

    out_file = tmpfile();
    if (!out_file) goto fail;

    /* Write input to in_file and rewind */
    if (input) {
        if (fwrite(input, 1, strlen(input), in_file) != strlen(input))
            goto fail;
    }
    if (fflush(in_file) != 0) goto fail;
    if (fseek(in_file, 0, SEEK_SET) != 0) goto fail;

    in_fd = fileno(in_file);
    out_fd = fileno(out_file);
    if (in_fd < 0 || out_fd < 0) goto fail;

    /* Save original fds */
    saved_stdin = dup(STDIN_FILENO);
    saved_stdout = dup(STDOUT_FILENO);
    if (saved_stdin < 0 || saved_stdout < 0) goto fail;

    /* Redirect stdin/stdout */
    if (dup2(in_fd, STDIN_FILENO) < 0) goto fail;
    if (dup2(out_fd, STDOUT_FILENO) < 0) goto fail;

    /* Configure initial-only behavior via global (declared in expand-common.h) */
    extern bool convert_entire_line;
    convert_entire_line = !initial_only;

    /* Call the function under test */
    expand();

    /* Ensure all output is flushed to out_file before restoring stdout */
    fflush(stdout);

    /* Restore stdout and stdin before any assertions/logging */
    if (dup2(saved_stdout, STDOUT_FILENO) < 0) goto fail;
    if (dup2(saved_stdin, STDIN_FILENO) < 0) goto fail;

    /* No longer need the saved fds */
    close(saved_stdout); saved_stdout = -1;
    close(saved_stdin); saved_stdin = -1;

    /* Read captured output */
    if (fflush(out_file) != 0) goto fail;
    if (fseek(out_file, 0, SEEK_END) != 0) goto fail;
    long sz = ftell(out_file);
    if (sz < 0) goto fail;
    if (fseek(out_file, 0, SEEK_SET) != 0) goto fail;

    out_buf = (char*)malloc((size_t)sz + 1);
    if (!out_buf) goto fail;

    if (sz > 0) {
        size_t rd = fread(out_buf, 1, (size_t)sz, out_file);
        if (rd != (size_t)sz) goto fail;
    }
    out_buf[sz] = '\0';

    /* Cleanup temp files */
    fclose(in_file);
    fclose(out_file);
    return out_buf;

fail:
    {
        int e = errno; /* preserve */
        if (saved_stdout >= 0) { dup2(saved_stdout, STDOUT_FILENO); close(saved_stdout); }
        if (saved_stdin  >= 0) { dup2(saved_stdin,  STDIN_FILENO);  close(saved_stdin); }
        if (in_file)  fclose(in_file);
        if (out_file) fclose(out_file);
        errno = e;
    }
    return NULL;
}

void setUp(void) {
    /* Default to full-line conversion before each test */
    extern bool convert_entire_line;
    convert_entire_line = true;
}

void tearDown(void) {
    /* Nothing to clean up */
}

/* Test: empty input -> empty output */
void test_expand_empty_input(void)
{
    char* out = run_expand_on_input("", false);
    TEST_ASSERT_NOT_NULL_MESSAGE(out, "run_expand_on_input failed");
    TEST_ASSERT_EQUAL_STRING("", out);
    free(out);
}

/* Test: basic single tab expansion with default tab size 8: "a<TAB>b\n" */
void test_expand_basic_single_tab(void)
{
    const char* in = "a\tb\n";
    const char* expected = "a       b\n"; /* 7 spaces between a and b */
    char* out = run_expand_on_input(in, false);
    TEST_ASSERT_NOT_NULL_MESSAGE(out, "run_expand_on_input failed");
    TEST_ASSERT_EQUAL_STRING(expected, out);
    free(out);
}

/* Test: two leading tabs expand to 16 spaces before newline */
void test_expand_two_leading_tabs(void)
{
    const char* in = "\t\t\n";
    const char* expected = "                \n"; /* 16 spaces then newline */
    char* out = run_expand_on_input(in, false);
    TEST_ASSERT_NOT_NULL_MESSAGE(out, "run_expand_on_input failed");
    TEST_ASSERT_EQUAL_STRING(expected, out);
    free(out);
}

/* Test: backspace affects column but is preserved in output */
void test_expand_backspace_behavior(void)
{
    /* After "abc", backspace moves back to col 2; tab then expands to col 8:
       6 spaces inserted, and backspace is preserved in output. */
    const char* in = "abc\b\tZ\n";
    const char* expected = "abc\b      Z\n"; /* backspace + 6 spaces */
    char* out = run_expand_on_input(in, false);
    TEST_ASSERT_NOT_NULL_MESSAGE(out, "run_expand_on_input failed");
    TEST_ASSERT_EQUAL_STRING(expected, out);
    free(out);
}

/* Test: initial-only mode (-i) on a single line */
void test_expand_initial_only_simple(void)
{
    /* Leading space + tab should expand to 8 spaces; after 'X' a following tab must remain */
    const char* in = " \tX\tY\n";
    const char* expected = "        X\tY\n"; /* 8 spaces, then X, then literal tab, then Y, nl */
    char* out = run_expand_on_input(in, true /* initial_only */);
    TEST_ASSERT_NOT_NULL_MESSAGE(out, "run_expand_on_input failed");
    TEST_ASSERT_EQUAL_STRING(expected, out);
    free(out);
}

/* Test: initial-only mode resets at each new line */
void test_expand_initial_only_resets_each_line(void)
{
    /* First line: leading tab converts; second line: leading tab converts again */
    const char* in = "\tA\n\tB\n";
    const char* expected = "        A\n        B\n";
    char* out = run_expand_on_input(in, true /* initial_only */);
    TEST_ASSERT_NOT_NULL_MESSAGE(out, "run_expand_on_input failed");
    TEST_ASSERT_EQUAL_STRING(expected, out);
    free(out);
}

/* Test: no trailing newline in input */
void test_expand_no_trailing_newline(void)
{
    const char* in = "A\tB";
    const char* expected = "A       B"; /* 7 spaces between A and B */
    char* out = run_expand_on_input(in, false);
    TEST_ASSERT_NOT_NULL_MESSAGE(out, "run_expand_on_input failed");
    TEST_ASSERT_EQUAL_STRING(expected, out);
    free(out);
}

int main(void)
{
    UNITY_BEGIN();
    RUN_TEST(test_expand_empty_input);
    RUN_TEST(test_expand_basic_single_tab);
    RUN_TEST(test_expand_two_leading_tabs);
    RUN_TEST(test_expand_backspace_behavior);
    RUN_TEST(test_expand_initial_only_simple);
    RUN_TEST(test_expand_initial_only_resets_each_line);
    RUN_TEST(test_expand_no_trailing_newline);
    return UNITY_END();
}