#include "../../unity/unity.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>

/* We rely on internal symbols from fmt.c:
   - static void set_prefix(char *p);
   - static int copy_rest(FILE *f, int c);
   - static bool tabs;
   - static int in_column;
   - static int next_prefix_indent;
   - static char const *prefix;
   - static int prefix_length;
   These are available since this test file is included into the same
   translation unit. */

/* Prototypes to silence any compiler warnings (available in this TU). */
static void set_prefix (char *p);
static int copy_rest (FILE *f, int c);

/* Globals from the program (declared in the same TU) */
extern bool tabs;
extern int in_column;
extern int next_prefix_indent;

/* Helper: create an input FILE* containing 'content' and rewind it. */
static FILE* make_input_stream(const char* content)
{
    FILE* f = tmpfile();
    if (!f)
        return NULL;
    size_t len = content ? strlen(content) : 0;
    if (len > 0)
    {
        if (fwrite(content, 1, len, f) != len)
        {
            fclose(f);
            return NULL;
        }
    }
    rewind(f);
    return f;
}

/* Helper: capture stdout while invoking copy_rest(fin, c).
   - Returns a heap-allocated string with the captured output (caller frees).
   - Writes the return value of copy_rest into *ret_c.
   - Returns NULL on failure (allocation or tmpfile issues).
   Note: No Unity assertions while stdout is redirected. */
static char* capture_copy_rest_output(FILE* fin, int c, int* ret_c)
{
    if (!ret_c)
        return NULL;

    fflush(stdout);
    int saved_fd = dup(fileno(stdout));
    if (saved_fd == -1)
        return NULL;

    FILE* cap = tmpfile();
    if (!cap)
    {
        close(saved_fd);
        return NULL;
    }
    int cap_fd = fileno(cap);
    if (dup2(cap_fd, fileno(stdout)) == -1)
    {
        fclose(cap);
        close(saved_fd);
        return NULL;
    }

    int r = copy_rest(fin, c);

    fflush(stdout);
    fflush(cap);

    /* Restore stdout */
    if (dup2(saved_fd, fileno(stdout)) == -1)
    {
        fclose(cap);
        close(saved_fd);
        return NULL;
    }
    close(saved_fd);

    /* Read captured output */
    if (fseek(cap, 0, SEEK_END) != 0)
    {
        fclose(cap);
        return NULL;
    }
    long sz = ftell(cap);
    if (sz < 0)
    {
        fclose(cap);
        return NULL;
    }
    if (fseek(cap, 0, SEEK_SET) != 0)
    {
        fclose(cap);
        return NULL;
    }

    char* buf = (char*)malloc((size_t)sz + 1);
    if (!buf)
    {
        fclose(cap);
        return NULL;
    }
    size_t nread = fread(buf, 1, (size_t)sz, cap);
    buf[nread] = '\0';
    fclose(cap);

    *ret_c = r;
    return buf;
}

void setUp(void)
{
    /* Ensure deterministic spacing (no tabs in output) */
    tabs = false;
}

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

/* Test: c == '\n' with no prefix progress; expect no output and return '\n'. */
static void test_copy_rest_blank_line_no_output(void)
{
    char pfx[] = "";
    set_prefix(pfx);
    next_prefix_indent = 0;
    in_column = 0;

    FILE* fin = make_input_stream("");
    TEST_ASSERT_NOT_NULL(fin);

    int retc = 0;
    char* out = capture_copy_rest_output(fin, '\n', &retc);
    fclose(fin);

    TEST_ASSERT_NOT_NULL(out);
    TEST_ASSERT_EQUAL_INT('\n', retc);
    TEST_ASSERT_EQUAL_UINT(0, strlen(out));
    free(out);
}

/* Test: c == '\n' with some indentation and partial prefix print. */
static void test_copy_rest_newline_with_partial_prefix(void)
{
    char pfx[] = "ABC";
    set_prefix(pfx);
    next_prefix_indent = 2; /* two leading spaces */
    in_column = 3;          /* matched 'A' before newline */

    FILE* fin = make_input_stream("");
    TEST_ASSERT_NOT_NULL(fin);

    int retc = 0;
    char* out = capture_copy_rest_output(fin, '\n', &retc);
    fclose(fin);

    TEST_ASSERT_NOT_NULL(out);
    TEST_ASSERT_EQUAL_INT('\n', retc);
    /* Expect: "  A" (2 spaces + 'A') */
    TEST_ASSERT_EQUAL_STRING("  A", out);
    free(out);
}

/* Test: mismatch (c not '\n'/EOF) with no extra padding beyond trimmed prefix. */
static void test_copy_rest_mismatch_no_padding(void)
{
    char pfx[] = "ABC";
    set_prefix(pfx);
    next_prefix_indent = 2;
    in_column = 3; /* matched 'A' */

    /* The remainder of the line (after 'X') will be "YZ\n" */
    FILE* fin = make_input_stream("YZ\n");
    TEST_ASSERT_NOT_NULL(fin);

    int retc = 0;
    char* out = capture_copy_rest_output(fin, 'X', &retc);
    fclose(fin);

    TEST_ASSERT_NOT_NULL(out);
    TEST_ASSERT_EQUAL_INT('\n', retc);
    /* Expect: "  A" + 'X' + "YZ" = "  AXYZ" */
    TEST_ASSERT_EQUAL_STRING("  AXYZ", out);
    free(out);
}

/* Test: mismatch with in_column beyond trimmed prefix -> extra padding spaces added. */
static void test_copy_rest_mismatch_with_padding_beyond_trimmed_prefix(void)
{
    char pfx[] = "AB   ";  /* trimmed prefix becomes "AB", prefix_length = 2 */
    set_prefix(pfx);
    next_prefix_indent = 1;
    in_column = next_prefix_indent + 4; /* 1 (indent) + 4 matched columns */

    /* After printing indent + "AB", we need (4 - 2) = 2 padding spaces. */
    FILE* fin = make_input_stream("T\n");
    TEST_ASSERT_NOT_NULL(fin);

    int retc = 0;
    char* out = capture_copy_rest_output(fin, 'X', &retc);
    fclose(fin);

    TEST_ASSERT_NOT_NULL(out);
    TEST_ASSERT_EQUAL_INT('\n', retc);
    /* Expect: " " + "AB" + "  " + 'X' + "T" = " AB  XT" */
    TEST_ASSERT_EQUAL_STRING(" AB  XT", out);
    free(out);
}

/* Test: EOF where in_column >= next_prefix_indent + prefix_length -> emits newline. */
static void test_copy_rest_eof_emits_newline_after_full_prefix(void)
{
    char pfx[] = "HELLO";
    set_prefix(pfx);
    next_prefix_indent = 3;
    in_column = next_prefix_indent + (int)strlen("HELLO"); /* full trimmed prefix matched */

    FILE* fin = make_input_stream("");
    TEST_ASSERT_NOT_NULL(fin);

    int retc = 0;
    char* out = capture_copy_rest_output(fin, EOF, &retc);
    fclose(fin);

    TEST_ASSERT_NOT_NULL(out);
    TEST_ASSERT_EQUAL_INT(EOF, retc);
    /* Expect: "   HELLO\n" */
    TEST_ASSERT_EQUAL_STRING("   HELLO\n", out);
    free(out);
}

/* Test: EOF where no progress beyond indent -> no output. */
static void test_copy_rest_eof_no_output_when_no_progress(void)
{
    char pfx[] = "HELLO";
    set_prefix(pfx);
    next_prefix_indent = 2;
    in_column = 2; /* no progress beyond indent */

    FILE* fin = make_input_stream("");
    TEST_ASSERT_NOT_NULL(fin);

    int retc = 0;
    char* out = capture_copy_rest_output(fin, EOF, &retc);
    fclose(fin);

    TEST_ASSERT_NOT_NULL(out);
    TEST_ASSERT_EQUAL_INT(EOF, retc);
    TEST_ASSERT_EQUAL_UINT(0, strlen(out));
    free(out);
}

/* Test: No prefix context (empty prefix), c not newline/EOF. */
static void test_copy_rest_no_prefix_context_non_newline(void)
{
    char pfx[] = "";
    set_prefix(pfx);
    next_prefix_indent = 0;
    in_column = 0;

    FILE* fin = make_input_stream("RS\n"); /* tail after 'Q' */
    TEST_ASSERT_NOT_NULL(fin);

    int retc = 0;
    char* out = capture_copy_rest_output(fin, 'Q', &retc);
    fclose(fin);

    TEST_ASSERT_NOT_NULL(out);
    TEST_ASSERT_EQUAL_INT('\n', retc);
    /* Expect: 'Q' + "RS" */
    TEST_ASSERT_EQUAL_STRING("QRS", out);
    free(out);
}

int main(void)
{
    UNITY_BEGIN();
    RUN_TEST(test_copy_rest_blank_line_no_output);
    RUN_TEST(test_copy_rest_newline_with_partial_prefix);
    RUN_TEST(test_copy_rest_mismatch_no_padding);
    RUN_TEST(test_copy_rest_mismatch_with_padding_beyond_trimmed_prefix);
    RUN_TEST(test_copy_rest_eof_emits_newline_after_full_prefix);
    RUN_TEST(test_copy_rest_eof_no_output_when_no_progress);
    RUN_TEST(test_copy_rest_no_prefix_context_non_newline);
    return UNITY_END();
}