use rand::prelude::*;

use rle::{HasLength, merge_items, SplitableSpan};

use content_tree::*;
use content_tree::testrange::TestRange;

fn random_entry(rng: &mut SmallRng) -> TestRange {
    TestRange {
        id: rng.gen_range(0..10),
        len: rng.gen_range(1..10),
        is_activated: rng.gen_bool(0.5)
    }
}

fn insert_into_list(list: &mut Vec<TestRange>, pos: usize, entry: TestRange) {
    let mut idx = 0;
    let mut cur_pos = 0;

    loop {
        if cur_pos == pos {
            list.insert(idx, entry);
            break;
        } else {
            let e = &list[idx];

            if cur_pos + e.len() > pos {
                // Split the item.
                let remainder = list[idx].truncate(pos - cur_pos);
                list.insert(idx + 1, entry);
                list.insert(idx + 2, remainder);
                break;
            }

            idx += 1;
            cur_pos += e.len();
        }
    }
}

fn delete_in_list(list: &mut Vec<TestRange>, pos: usize, mut del_span: usize) {
    let mut idx = 0;
    let mut cur_pos = 0;

    while del_span > 0 && idx < list.len() {
        let e_len = list[idx].len();
        if cur_pos == pos {
            if e_len > del_span {
                list[idx].truncate_keeping_right(del_span);
                break;
            } else {
                del_span -= e_len;
                list.remove(idx);
                // And continue keeping the current index.
            }
        } else {
            if cur_pos + e_len > pos {
                // Split the item.
                let mut remainder = list[idx].truncate(pos - cur_pos);
                if del_span < remainder.len() {
                    remainder.truncate_keeping_right(del_span);
                    list.insert(idx + 1, remainder);
                    return;
                } else {
                    // Discard r1.
                    del_span -= remainder.len();
                }
            }

            cur_pos += list[idx].len();
            idx += 1;
        }
    }
}

fn replace_in_list(list: &mut Vec<TestRange>, pos: usize, entry: TestRange) {
    // Wheee testing laziness!
    delete_in_list(list, pos, entry.len());
    insert_into_list(list, pos, entry);
}

fn random_edits_once(verbose: bool, iterations: usize) {
    let mut rng = SmallRng::seed_from_u64(20);

    // So for this test we'll make a range tree and a list, make random changes to both, and make
    // sure the content is always the same.

    for _i in 0..iterations {
        if verbose || _i % 10000 == 0 { println!("i {}", _i); }
        // TestRange is overkill for this, but eh.
        let mut tree = ContentTreeRaw::<TestRange, FullMetricsU32, DEFAULT_IE, DEFAULT_LE>::new();
        let mut list = vec![];
        let mut expected_len = 0;

        for _j in 0..200 {
            if verbose { println!("  j {} / i {}", _j, _i); }
            if list.is_empty() || rng.gen_bool(0.33) {
                // Insert something.
                let pos = rng.gen_range(0..=tree.len().0);
                let item = random_entry(&mut rng);

                if verbose { println!("inserting {:?} at {}", item, pos); }
                // dbg!(&tree);
                let mut cursor = tree.mut_cursor_at_offset_pos(pos as usize, true);
                assert_eq!(cursor.count_offset_pos() as u32, pos);
                cursor.check();

                cursor.insert(item);
                assert_eq!(cursor.count_offset_pos() as u32, pos + item.len);
                cursor.check();

                insert_into_list(&mut list, pos as usize, item);

                expected_len += item.len();
            } else if tree.content_len() > 10 && rng.gen_bool(0.5) {
                // Modify something.
                let item = random_entry(&mut rng);
                // let pos = rng.gen_range(0..tree.count.0 - item.len);
                let pos = rng.gen_range(0..=tree.offset_len() as u32);

                if verbose {
                    println!("Replacing {} entries at position {} with {:?}", item.len(), pos, item);
                }
                let mut cursor = tree.mut_cursor_at_offset_pos(pos as usize, true);
                assert_eq!(cursor.count_offset_pos() as u32, pos);
                cursor.check();
                cursor.replace_range(item);
                assert_eq!(cursor.count_offset_pos() as u32, pos + item.len);
                cursor.check();

                replace_in_list(&mut list, pos as usize, item);

                // this could be cleaned up but eh.
                let amt_deleted = usize::min(item.len(), expected_len - pos as usize);
                expected_len = expected_len - amt_deleted + item.len();
            } else {
                // Delete something
                assert!(tree.offset_len() > 0);

                // Delete up to 20 items, but not more than we have in the document!
                // let del_span = rng.gen_range(1..=u32::min(tree.count.0, 20));
                let del_span = rng.gen_range(0..=20);
                // let pos = rng.gen_range(0..=tree.count.0 - del_span);
                let pos = rng.gen_range(0..=tree.offset_len() as u32);

                if verbose {
                    println!("Deleting {} entries at position {} (size {})", pos, del_span, expected_len);
                }
                let mut cursor = tree.mut_cursor_at_offset_pos(pos as usize, true);
                assert_eq!(cursor.count_offset_pos() as u32, pos);
                cursor.check();

                cursor.delete(del_span as _);
                assert_eq!(cursor.count_offset_pos() as u32, pos);
                cursor.check();

                delete_in_list(&mut list, pos as usize, del_span as usize);

                // expected_len -= del_span as usize;
                let amt_deleted = usize::min(expected_len - pos as usize, del_span as usize);
                expected_len -= amt_deleted;
            }

            tree.check();

            let list_len = list.iter().fold(0usize, |sum, item| sum + item.len());
            assert_eq!(expected_len, list_len);
            assert_eq!(expected_len, tree.offset_len());

            let list_content = list.iter().fold(0usize, |sum, item| sum + item.content_len());
            assert_eq!(list_content, tree.content_len());

            let tree_iter = merge_items(tree.raw_iter());
            let list_iter = merge_items(list.iter().copied());
            assert!(tree_iter.eq(list_iter));
        }
    }
}

#[test]
fn random_edits() {
    random_edits_once(false, 300);
}

#[test]
#[ignore]
fn random_edits_forever() {
    random_edits_once(false, usize::MAX);
}