    const std = @import("std.zig");
    const mem = std.mem;

    /// Comptime string map optimized for small sets of disparate string keys.
    /// Works by separating the keys by length at comptime and only checking strings of
    /// equal length at runtime.
    ///
    /// `kvs_list` expects a list of `struct { []const u8, V }` (key-value pair) tuples.
    /// You can pass `struct { []const u8 }` (only keys) tuples if `V` is `void`.
    pub fn ComptimeStringMap(comptime V: type, comptime kvs_list: anytype) type {
        const precomputed = comptime blk: {
            @setEvalBranchQuota(1500);
            const KV = struct {
                key: []const u8,
                value: V,
            };
            var sorted_kvs: [kvs_list.len]KV = undefined;
            for (kvs_list, 0..) |kv, i| {
                if (V != void) {
                    sorted_kvs[i] = .{ .key = kv.@"0", .value = kv.@"1" };
                } else {
                    sorted_kvs[i] = .{ .key = kv.@"0", .value = {} };
                }
            }

            const SortContext = struct {
                kvs: []KV,

                pub fn lessThan(ctx: @This(), a: usize, b: usize) bool {
                    return ctx.kvs[a].key.len < ctx.kvs[b].key.len;
                }

                pub fn swap(ctx: @This(), a: usize, b: usize) void {
                    return std.mem.swap(KV, &ctx.kvs[a], &ctx.kvs[b]);
                }
            };
            mem.sortUnstableContext(0, sorted_kvs.len, SortContext{ .kvs = &sorted_kvs });

            const min_len = sorted_kvs[0].key.len;
            const max_len = sorted_kvs[sorted_kvs.len - 1].key.len;
            var len_indexes: [max_len + 1]usize = undefined;
            var len: usize = 0;
            var i: usize = 0;
            while (len <= max_len) : (len += 1) {
                // find the first keyword len == len

                while (len > sorted_kvs[i].key.len) {
                    i += 1;
                }
                len_indexes[len] = i;
            }
            break :blk .{
                .min_len = min_len,
                .max_len = max_len,
                .sorted_kvs = sorted_kvs,
                .len_indexes = len_indexes,
            };
        };

        return struct {
            /// Array of `struct { key: []const u8, value: V }` where `value` is `void{}` if `V` is `void`.
            /// Sorted by `key` length.
            pub const kvs = precomputed.sorted_kvs;

            /// Checks if the map has a value for the key.
            pub fn has(str: []const u8) bool {
                return get(str) != null;
            }

            /// Returns the value for the key if any, else null.
            pub fn get(str: []const u8) ?V {
                if (str.len < precomputed.min_len or str.len > precomputed.max_len)
                    return null;

                var i = precomputed.len_indexes[str.len];
                while (true) {
                    const kv = precomputed.sorted_kvs[i];
                    if (kv.key.len != str.len)
                        return null;
                    if (mem.eql(u8, kv.key, str))
                        return kv.value;
                    i += 1;
                    if (i >= precomputed.sorted_kvs.len)
                        return null;
                }
            }
        };
    }

    const TestEnum = enum {
        A,
        B,
        C,
        D,
        E,
    };

    test "ComptimeStringMap list literal of list literals" {
        const map = ComptimeStringMap(TestEnum, .{
            .{ "these", .D },
            .{ "have", .A },
            .{ "nothing", .B },
            .{ "incommon", .C },
            .{ "samelen", .E },
        });

        try testMap(map);
    }

    test "ComptimeStringMap array of structs" {
        const KV = struct { []const u8, TestEnum };
        const map = ComptimeStringMap(TestEnum, [_]KV{
            .{ "these", .D },
            .{ "have", .A },
            .{ "nothing", .B },
            .{ "incommon", .C },
            .{ "samelen", .E },
        });

        try testMap(map);
    }

    test "ComptimeStringMap slice of structs" {
        const KV = struct { []const u8, TestEnum };
        const slice: []const KV = &[_]KV{
            .{ "these", .D },
            .{ "have", .A },
            .{ "nothing", .B },
            .{ "incommon", .C },
            .{ "samelen", .E },
        };
        const map = ComptimeStringMap(TestEnum, slice);

        try testMap(map);
    }

    fn testMap(comptime map: anytype) !void {
        try std.testing.expectEqual(TestEnum.A, map.get("have").?);
        try std.testing.expectEqual(TestEnum.B, map.get("nothing").?);
        try std.testing.expect(null == map.get("missing"));
        try std.testing.expectEqual(TestEnum.D, map.get("these").?);
        try std.testing.expectEqual(TestEnum.E, map.get("samelen").?);

        try std.testing.expect(!map.has("missing"));
        try std.testing.expect(map.has("these"));
    }

    test "ComptimeStringMap void value type, slice of structs" {
        const KV = struct { []const u8 };
        const slice: []const KV = &[_]KV{
            .{"these"},
            .{"have"},
            .{"nothing"},
            .{"incommon"},
            .{"samelen"},
        };
        const map = ComptimeStringMap(void, slice);

        try testSet(map);
    }

    test "ComptimeStringMap void value type, list literal of list literals" {
        const map = ComptimeStringMap(void, .{
            .{"these"},
            .{"have"},
            .{"nothing"},
            .{"incommon"},
            .{"samelen"},
        });

        try testSet(map);
    }

    fn testSet(comptime map: anytype) !void {
        try std.testing.expectEqual({}, map.get("have").?);
        try std.testing.expectEqual({}, map.get("nothing").?);
        try std.testing.expect(null == map.get("missing"));
        try std.testing.expectEqual({}, map.get("these").?);
        try std.testing.expectEqual({}, map.get("samelen").?);

        try std.testing.expect(!map.has("missing"));
        try std.testing.expect(map.has("these"));
    }