#include <unity.h>

#include <algorithm>
#include <cstring>
#include <string>

#include "text_pager.h"

using namespace roro::files;

void setUp() {}
void tearDown() {}

static int reads = 0;
static size_t biggestRead = 0;

static TextPager pagerFor(const std::string& text, int cols, int rows) {
    return TextPager(
        [&text](uint32_t offset, uint8_t* into, size_t len) {
            reads++;
            biggestRead = std::max(biggestRead, len);
            if (offset >= text.size()) return static_cast<size_t>(0);
            size_t n = std::min(len, text.size() - offset);
            std::memcpy(into, text.data() + offset, n);
            return n;
        },
        static_cast<uint32_t>(text.size()), cols, rows);
}

void test_lines_and_wrapping() {
    std::string text = "one\r\ntwo words that are too long\n\nlast";
    TextPager p = pagerFor(text, 10, 8);
    auto lines = p.lines();
    TEST_ASSERT_EQUAL_size_t(6, lines.size());
    TEST_ASSERT_EQUAL_STRING("one", lines[0].c_str());  // the \r is dropped
    TEST_ASSERT_EQUAL_STRING("two words", lines[1].c_str());
    TEST_ASSERT_EQUAL_STRING("that are", lines[2].c_str());
    TEST_ASSERT_EQUAL_STRING("too long", lines[3].c_str());
    TEST_ASSERT_EQUAL_STRING("", lines[4].c_str());
    TEST_ASSERT_EQUAL_STRING("last", lines[5].c_str());
    TEST_ASSERT_TRUE(p.atEnd());
}

void test_a_word_too_long_is_cut_and_a_space_at_the_edge_is_eaten() {
    std::string text = "abcdefghijklmno\nabcde fghij klm";
    TextPager p = pagerFor(text, 5, 8);
    auto lines = p.lines();
    TEST_ASSERT_EQUAL_STRING("abcde", lines[0].c_str());
    TEST_ASSERT_EQUAL_STRING("fghij", lines[1].c_str());
    TEST_ASSERT_EQUAL_STRING("klmno", lines[2].c_str());
    TEST_ASSERT_EQUAL_STRING("abcde", lines[3].c_str());
    TEST_ASSERT_EQUAL_STRING("fghij", lines[4].c_str());
    TEST_ASSERT_EQUAL_STRING("klm", lines[5].c_str());
}

void test_accents_count_as_one_column_and_tabs_show_as_spaces() {
    std::string text = "\xC3\xA9t\xC3\xA9 ici\n\ta\x01";
    TextPager p = pagerFor(text, 3, 4);
    auto lines = p.lines();
    TEST_ASSERT_EQUAL_STRING("\xC3\xA9t\xC3\xA9", lines[0].c_str());
    TEST_ASSERT_EQUAL_STRING("ici", lines[1].c_str());
    TEST_ASSERT_EQUAL_STRING(" a.", lines[2].c_str());
}

// Scrolling down to the end and back up passes through the same line starts.
void test_up_undoes_down() {
    std::string text;
    for (int i = 0; i < 300; i++) {
        text += "line " + std::to_string(i) + " with some words to wrap around the edge of the screen";
        text += i % 7 == 0 ? "\n\n" : "\n";
    }
    text += "a paragraph without any newline for a long while ";
    for (int i = 0; i < 200; i++) text += "word" + std::to_string(i) + " ";
    text += "\nthe end";
    TextPager p = pagerFor(text, 38, 9);
    std::vector<uint32_t> tops;
    for (int guard = 0; guard < 5000 && !p.atEnd(); guard++) {
        tops.push_back(p.top());
        p.down();
    }
    TEST_ASSERT_TRUE(p.atEnd());
    TEST_ASSERT_TRUE(tops.size() > 500);
    TEST_ASSERT_EQUAL_STRING("the end", p.lines().back().c_str());
    // Inside the long paragraph (further than the look-back from its start) lines may wrap from
    // another place on the way up. Before it, every line start met on the way down is met again.
    size_t paragraph = text.find("a paragraph without");
    size_t expected = 0, met = 0;
    for (uint32_t t : tops) expected += t <= paragraph;
    for (int guard = 0; guard < 5000 && p.top() > 0; guard++) {
        p.up();
        if (p.top() > paragraph) continue;
        TEST_ASSERT_TRUE(std::binary_search(tops.begin(), tops.end(), p.top()));
        met++;
    }
    TEST_ASSERT_EQUAL_size_t(expected, met);
    TEST_ASSERT_EQUAL_UINT32(0, p.top());
    p.up();
    TEST_ASSERT_EQUAL_UINT32(0, p.top());
}

void test_to_end_shows_the_last_lines() {
    std::string text;
    for (int i = 0; i < 100; i++) text += "20:0" + std::to_string(i % 10) + " <a> message " + std::to_string(i) + "\n";
    TextPager p = pagerFor(text, 38, 9);
    p.toEnd();
    auto lines = p.lines();
    TEST_ASSERT_EQUAL_size_t(9, lines.size());
    TEST_ASSERT_EQUAL_STRING("20:09 <a> message 99", lines[8].c_str());
    TEST_ASSERT_EQUAL_STRING("20:01 <a> message 91", lines[0].c_str());
    TEST_ASSERT_TRUE(p.atEnd());
    p.down();  // nowhere to go
    TEST_ASSERT_EQUAL_STRING("20:01 <a> message 91", p.lines()[0].c_str());
    TEST_ASSERT_TRUE(p.percent() > 80);
}

void test_a_megabyte_is_read_a_kilobyte_at_a_time() {
    std::string text;
    while (text.size() < 1024 * 1024) text += "2026-10-05 20:00:00 <someone> says something here\n";
    reads = 0;
    biggestRead = 0;
    TextPager p = pagerFor(text, 38, 9);
    p.toEnd();
    TEST_ASSERT_EQUAL_size_t(9, p.lines().size());
    p.up(20);
    p.down(5);
    TEST_ASSERT_TRUE(biggestRead <= 1024);
    TEST_ASSERT_TRUE(reads < 20);
    p.toStart();
    TEST_ASSERT_EQUAL_STRING("2026-10-05 20:00:00 <someone> says", p.lines()[0].c_str());
}

void test_empty_and_short_files() {
    std::string empty;
    TextPager p = pagerFor(empty, 38, 9);
    TEST_ASSERT_EQUAL_size_t(0, p.lines().size());
    p.down();
    p.up();
    p.toEnd();
    TEST_ASSERT_TRUE(p.atEnd());
    std::string one = "no newline";
    TextPager q = pagerFor(one, 38, 9);
    q.toEnd();
    TEST_ASSERT_EQUAL_STRING("no newline", q.lines()[0].c_str());
}

int main() {
    UNITY_BEGIN();
    RUN_TEST(test_lines_and_wrapping);
    RUN_TEST(test_a_word_too_long_is_cut_and_a_space_at_the_edge_is_eaten);
    RUN_TEST(test_accents_count_as_one_column_and_tabs_show_as_spaces);
    RUN_TEST(test_up_undoes_down);
    RUN_TEST(test_to_end_shows_the_last_lines);
    RUN_TEST(test_a_megabyte_is_read_a_kilobyte_at_a_time);
    RUN_TEST(test_empty_and_short_files);
    return UNITY_END();
}