const std = @import("std.zig");
const assert = std.debug.assert;
const mem = std.mem;
const testing = std.testing;
pub fn BoundedArray(comptime T: type, comptime buffer_capacity: usize) type {
    return struct {
        const Self = @This();
        buffer: [buffer_capacity]T = undefined,
        len: usize = 0,
        
        
        pub fn init(len: usize) error{Overflow}!Self {
            if (len > buffer_capacity) return error.Overflow;
            return Self{ .len = len };
        }
        
        pub fn slice(self: anytype) mem.Span(@TypeOf(&self.buffer)) {
            return self.buffer[0..self.len];
        }
        
        pub fn constSlice(self: *const Self) []const T {
            return self.slice();
        }
        
        
        pub fn resize(self: *Self, len: usize) error{Overflow}!void {
            if (len > buffer_capacity) return error.Overflow;
            self.len = len;
        }
        
        pub fn fromSlice(m: []const T) error{Overflow}!Self {
            var list = try init(m.len);
            std.mem.copy(T, list.slice(), m);
            return list;
        }
        
        pub fn get(self: Self, i: usize) T {
            return self.constSlice()[i];
        }
        
        pub fn set(self: *Self, i: usize, item: T) void {
            self.slice()[i] = item;
        }
        
        pub fn capacity(self: Self) usize {
            return self.buffer.len;
        }
        
        pub fn ensureUnusedCapacity(self: Self, additional_count: usize) error{Overflow}!void {
            if (self.len + additional_count > buffer_capacity) {
                return error.Overflow;
            }
        }
        
        pub fn addOne(self: *Self) error{Overflow}!*T {
            try self.ensureUnusedCapacity(1);
            return self.addOneAssumeCapacity();
        }
        
        
        pub fn addOneAssumeCapacity(self: *Self) *T {
            assert(self.len < buffer_capacity);
            self.len += 1;
            return &self.slice()[self.len - 1];
        }
        
        
        pub fn addManyAsArray(self: *Self, comptime n: usize) error{Overflow}!*[n]T {
            const prev_len = self.len;
            try self.resize(self.len + n);
            return self.slice()[prev_len..][0..n];
        }
        
        
        pub fn pop(self: *Self) T {
            const item = self.get(self.len - 1);
            self.len -= 1;
            return item;
        }
        
        
        pub fn popOrNull(self: *Self) ?T {
            return if (self.len == 0) null else self.pop();
        }
        
        
        
        
        pub fn unusedCapacitySlice(self: *Self) []T {
            return self.buffer[self.len..];
        }
        
        
        pub fn insert(
            self: *Self,
            i: usize,
            item: T,
        ) error{Overflow}!void {
            if (i > self.len) {
                return error.Overflow;
            }
            _ = try self.addOne();
            var s = self.slice();
            mem.copyBackwards(T, s[i + 1 .. s.len], s[i .. s.len - 1]);
            self.buffer[i] = item;
        }
        
        
        pub fn insertSlice(self: *Self, i: usize, items: []const T) error{Overflow}!void {
            try self.ensureUnusedCapacity(items.len);
            self.len += items.len;
            mem.copyBackwards(T, self.slice()[i + items.len .. self.len], self.constSlice()[i .. self.len - items.len]);
            mem.copy(T, self.slice()[i .. i + items.len], items);
        }
        
        
        
        pub fn replaceRange(
            self: *Self,
            start: usize,
            len: usize,
            new_items: []const T,
        ) error{Overflow}!void {
            const after_range = start + len;
            var range = self.slice()[start..after_range];
            if (range.len == new_items.len) {
                mem.copy(T, range, new_items);
            } else if (range.len < new_items.len) {
                const first = new_items[0..range.len];
                const rest = new_items[range.len..];
                mem.copy(T, range, first);
                try self.insertSlice(after_range, rest);
            } else {
                mem.copy(T, range, new_items);
                const after_subrange = start + new_items.len;
                for (self.constSlice()[after_range..]) |item, i| {
                    self.slice()[after_subrange..][i] = item;
                }
                self.len -= len - new_items.len;
            }
        }
        
        pub fn append(self: *Self, item: T) error{Overflow}!void {
            const new_item_ptr = try self.addOne();
            new_item_ptr.* = item;
        }
        
        
        pub fn appendAssumeCapacity(self: *Self, item: T) void {
            const new_item_ptr = self.addOneAssumeCapacity();
            new_item_ptr.* = item;
        }
        
        
        
        
        pub fn orderedRemove(self: *Self, i: usize) T {
            const newlen = self.len - 1;
            if (newlen == i) return self.pop();
            const old_item = self.get(i);
            for (self.slice()[i..newlen]) |*b, j| b.* = self.get(i + 1 + j);
            self.set(newlen, undefined);
            self.len = newlen;
            return old_item;
        }
        
        
        
        pub fn swapRemove(self: *Self, i: usize) T {
            if (self.len - 1 == i) return self.pop();
            const old_item = self.get(i);
            self.set(i, self.pop());
            return old_item;
        }
        
        pub fn appendSlice(self: *Self, items: []const T) error{Overflow}!void {
            try self.ensureUnusedCapacity(items.len);
            self.appendSliceAssumeCapacity(items);
        }
        
        
        pub fn appendSliceAssumeCapacity(self: *Self, items: []const T) void {
            const oldlen = self.len;
            self.len += items.len;
            mem.copy(T, self.slice()[oldlen..], items);
        }
        
        
        pub fn appendNTimes(self: *Self, value: T, n: usize) error{Overflow}!void {
            const old_len = self.len;
            try self.resize(old_len + n);
            mem.set(T, self.slice()[old_len..self.len], value);
        }
        
        
        pub fn appendNTimesAssumeCapacity(self: *Self, value: T, n: usize) void {
            const old_len = self.len;
            self.len += n;
            assert(self.len <= buffer_capacity);
            mem.set(T, self.slice()[old_len..self.len], value);
        }
        pub const Writer = if (T != u8)
            @compileError("The Writer interface is only defined for BoundedArray(u8, ...) " ++
                "but the given type is BoundedArray(" ++ @typeName(T) ++ ", ...)")
        else
            std.io.Writer(*Self, error{Overflow}, appendWrite);
        
        pub fn writer(self: *Self) Writer {
            return .{ .context = self };
        }
        
        
        fn appendWrite(self: *Self, m: []const u8) error{Overflow}!usize {
            try self.appendSlice(m);
            return m.len;
        }
    };
}
test "BoundedArray" {
    var a = try BoundedArray(u8, 64).init(32);
    try testing.expectEqual(a.capacity(), 64);
    try testing.expectEqual(a.slice().len, 32);
    try testing.expectEqual(a.constSlice().len, 32);
    try a.resize(48);
    try testing.expectEqual(a.len, 48);
    const x = [_]u8{1} ** 10;
    a = try BoundedArray(u8, 64).fromSlice(&x);
    try testing.expectEqualSlices(u8, &x, a.constSlice());
    var a2 = a;
    try testing.expectEqualSlices(u8, a.constSlice(), a2.constSlice());
    a2.set(0, 0);
    try testing.expect(a.get(0) != a2.get(0));
    try testing.expectError(error.Overflow, a.resize(100));
    try testing.expectError(error.Overflow, BoundedArray(u8, x.len - 1).fromSlice(&x));
    try a.resize(0);
    try a.ensureUnusedCapacity(a.capacity());
    (try a.addOne()).* = 0;
    try a.ensureUnusedCapacity(a.capacity() - 1);
    try testing.expectEqual(a.len, 1);
    const uninitialized = try a.addManyAsArray(4);
    try testing.expectEqual(uninitialized.len, 4);
    try testing.expectEqual(a.len, 5);
    try a.append(0xff);
    try testing.expectEqual(a.len, 6);
    try testing.expectEqual(a.pop(), 0xff);
    a.appendAssumeCapacity(0xff);
    try testing.expectEqual(a.len, 6);
    try testing.expectEqual(a.pop(), 0xff);
    try a.resize(1);
    try testing.expectEqual(a.popOrNull(), 0);
    try testing.expectEqual(a.popOrNull(), null);
    var unused = a.unusedCapacitySlice();
    mem.set(u8, unused[0..8], 2);
    unused[8] = 3;
    unused[9] = 4;
    try testing.expectEqual(unused.len, a.capacity());
    try a.resize(10);
    try a.insert(5, 0xaa);
    try testing.expectEqual(a.len, 11);
    try testing.expectEqual(a.get(5), 0xaa);
    try testing.expectEqual(a.get(9), 3);
    try testing.expectEqual(a.get(10), 4);
    try a.insert(11, 0xbb);
    try testing.expectEqual(a.len, 12);
    try testing.expectEqual(a.pop(), 0xbb);
    try a.appendSlice(&x);
    try testing.expectEqual(a.len, 11 + x.len);
    try a.appendNTimes(0xbb, 5);
    try testing.expectEqual(a.len, 11 + x.len + 5);
    try testing.expectEqual(a.pop(), 0xbb);
    a.appendNTimesAssumeCapacity(0xcc, 5);
    try testing.expectEqual(a.len, 11 + x.len + 5 - 1 + 5);
    try testing.expectEqual(a.pop(), 0xcc);
    try testing.expectEqual(a.len, 29);
    try a.replaceRange(1, 20, &x);
    try testing.expectEqual(a.len, 29 + x.len - 20);
    try a.insertSlice(0, &x);
    try testing.expectEqual(a.len, 29 + x.len - 20 + x.len);
    try a.replaceRange(1, 5, &x);
    try testing.expectEqual(a.len, 29 + x.len - 20 + x.len + x.len - 5);
    try a.append(10);
    try testing.expectEqual(a.pop(), 10);
    try a.append(20);
    const removed = a.orderedRemove(5);
    try testing.expectEqual(removed, 1);
    try testing.expectEqual(a.len, 34);
    a.set(0, 0xdd);
    a.set(a.len - 1, 0xee);
    const swapped = a.swapRemove(0);
    try testing.expectEqual(swapped, 0xdd);
    try testing.expectEqual(a.get(0), 0xee);
    while (a.popOrNull()) |_| {}
    const w = a.writer();
    const s = "hello, this is a test string";
    try w.writeAll(s);
    try testing.expectEqualStrings(s, a.constSlice());
}