chore(tazjin/predlozhnik): move to //corp r/5678

This is currently hosted by the company, and I'm assigning my
copyright to the company, which also runs an ad placement on the page.

Note that the NixOS module for hosting it has not been moved yet.

Change-Id: Iba9e1cab9370faa79e43c3344fbfbbbabead50b3
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7857
Reviewed-by: tazjin <tazjin@tvl.su>
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

8 files changed, 934 insertions, 0 deletions

diff --git a/corp/russian/README.md b/corp/russian/README.md
new file mode 100644
index 0000000000..23c3d594c8
--- /dev/null
+++ b/corp/russian/README.md
@@ -0,0 +1,9 @@
+//corp/russian
+==============
+
+This folder contains TVL corp projects related to the Russian
+language, such as the code powering
+[Предложник](https://predlozhnik.ru).
+
+Unless otherwise specified, all rights to these projects are reserved
+by ООО "ТВЛ".
diff --git a/corp/russian/predlozhnik/.gitignore b/corp/russian/predlozhnik/.gitignore
new file mode 100644
index 0000000000..58eaf3e326
--- /dev/null
+++ b/corp/russian/predlozhnik/.gitignore
@@ -0,0 +1,3 @@
+/target/
+**/*.rs.bk
+dist/
diff --git a/corp/russian/predlozhnik/Cargo.lock b/corp/russian/predlozhnik/Cargo.lock
new file mode 100644
index 0000000000..131aa134fe
--- /dev/null
+++ b/corp/russian/predlozhnik/Cargo.lock
@@ -0,0 +1,460 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "autocfg"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d468802bab17cbc0cc575e9b053f41e72aa36bfa6b7f55e3529ffa43161b97fa"
+
+[[package]]
+name = "boolinator"
+version = "2.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cfa8873f51c92e232f9bac4065cddef41b714152812bfc5f7672ba16d6ef8cd9"
+
+[[package]]
+name = "bumpalo"
+version = "3.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c1ad822118d20d2c234f427000d5acc36eabe1e29a348c89b63dd60b13f28e5d"
+
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
+[[package]]
+name = "console_error_panic_hook"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a06aeb73f470f66dcdbf7223caeebb85984942f22f1adb2a088cf9668146bbbc"
+dependencies = [
+ "cfg-if",
+ "wasm-bindgen",
+]
+
+[[package]]
+name = "gloo"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "23947965eee55e3e97a5cd142dd4c10631cc349b48cecca0ed230fd296f568cd"
+dependencies = [
+ "gloo-console",
+ "gloo-dialogs",
+ "gloo-events",
+ "gloo-file",
+ "gloo-render",
+ "gloo-storage",
+ "gloo-timers",
+ "gloo-utils",
+]
+
+[[package]]
+name = "gloo-console"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "82b7ce3c05debe147233596904981848862b068862e9ec3e34be446077190d3f"
+dependencies = [
+ "gloo-utils",
+ "js-sys",
+ "serde",
+ "wasm-bindgen",
+ "web-sys",
+]
+
+[[package]]
+name = "gloo-dialogs"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "67062364ac72d27f08445a46cab428188e2e224ec9e37efdba48ae8c289002e6"
+dependencies = [
+ "wasm-bindgen",
+ "web-sys",
+]
+
+[[package]]
+name = "gloo-events"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "68b107f8abed8105e4182de63845afcc7b69c098b7852a813ea7462a320992fc"
+dependencies = [
+ "wasm-bindgen",
+ "web-sys",
+]
+
+[[package]]
+name = "gloo-file"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a8d5564e570a38b43d78bdc063374a0c3098c4f0d64005b12f9bbe87e869b6d7"
+dependencies = [
+ "gloo-events",
+ "js-sys",
+ "wasm-bindgen",
+ "web-sys",
+]
+
+[[package]]
+name = "gloo-render"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2fd9306aef67cfd4449823aadcd14e3958e0800aa2183955a309112a84ec7764"
+dependencies = [
+ "wasm-bindgen",
+ "web-sys",
+]
+
+[[package]]
+name = "gloo-storage"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5d6ab60bf5dbfd6f0ed1f7843da31b41010515c745735c970e821945ca91e480"
+dependencies = [
+ "gloo-utils",
+ "js-sys",
+ "serde",
+ "serde_json",
+ "thiserror",
+ "wasm-bindgen",
+ "web-sys",
+]
+
+[[package]]
+name = "gloo-timers"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5fb7d06c1c8cc2a29bee7ec961009a0b2caa0793ee4900c2ffb348734ba1c8f9"
+dependencies = [
+ "js-sys",
+ "wasm-bindgen",
+]
+
+[[package]]
+name = "gloo-utils"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "40913a05c8297adca04392f707b1e73b12ba7b8eab7244a4961580b1fd34063c"
+dependencies = [
+ "js-sys",
+ "serde",
+ "serde_json",
+ "wasm-bindgen",
+ "web-sys",
+]
+
+[[package]]
+name = "hashbrown"
+version = "0.12.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8a9ee70c43aaf417c914396645a0fa852624801b24ebb7ae78fe8272889ac888"
+
+[[package]]
+name = "indexmap"
+version = "1.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "10a35a97730320ffe8e2d410b5d3b69279b98d2c14bdb8b70ea89ecf7888d41e"
+dependencies = [
+ "autocfg",
+ "hashbrown",
+]
+
+[[package]]
+name = "itoa"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6c8af84674fe1f223a982c933a0ee1086ac4d4052aa0fb8060c12c6ad838e754"
+
+[[package]]
+name = "js-sys"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49409df3e3bf0856b916e2ceaca09ee28e6871cf7d9ce97a692cacfdb2a25a47"
+dependencies = [
+ "wasm-bindgen",
+]
+
+[[package]]
+name = "lazy_static"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
+
+[[package]]
+name = "log"
+version = "0.4.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "abb12e687cfb44aa40f41fc3978ef76448f9b6038cad6aef4259d3c095a2382e"
+dependencies = [
+ "cfg-if",
+]
+
+[[package]]
+name = "maplit"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3e2e65a1a2e43cfcb47a895c4c8b10d1f4a61097f9f254f183aee60cad9c651d"
+
+[[package]]
+name = "once_cell"
+version = "1.15.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e82dad04139b71a90c080c8463fe0dc7902db5192d939bd0950f074d014339e1"
+
+[[package]]
+name = "predlozhnik"
+version = "0.1.0"
+dependencies = [
+ "lazy_static",
+ "maplit",
+ "wasm-bindgen",
+ "yew",
+]
+
+[[package]]
+name = "proc-macro-error"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da25490ff9892aab3fcf7c36f08cfb902dd3e71ca0f9f9517bea02a73a5ce38c"
+dependencies = [
+ "proc-macro-error-attr",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro-error-attr"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1be40180e52ecc98ad80b184934baf3d0d29f979574e439af5a55274b35f869"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "version_check",
+]
+
+[[package]]
+name = "proc-macro2"
+version = "1.0.46"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "94e2ef8dbfc347b10c094890f778ee2e36ca9bb4262e86dc99cd217e35f3470b"
+dependencies = [
+ "unicode-ident",
+]
+
+[[package]]
+name = "quote"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
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+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4501abdff3ae82a1c1b477a17252eb69cee9e66eb915c1abaa4f44d873df9f09"
+
+[[package]]
+name = "scoped-tls-hkt"
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+
+[[package]]
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+checksum = "728eb6351430bccb993660dfffc5a72f91ccc1295abaa8ce19b27ebe4f75568b"
+dependencies = [
+ "serde_derive",
+]
+
+[[package]]
+name = "serde_derive"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "81fa1584d3d1bcacd84c277a0dfe21f5b0f6accf4a23d04d4c6d61f1af522b4c"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "serde_json"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
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+dependencies = [
+ "itoa",
+ "ryu",
+ "serde",
+]
+
+[[package]]
+name = "slab"
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4614a76b2a8be0058caa9dbbaf66d988527d86d003c11a94fbd335d7661edcef"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
+name = "syn"
+version = "1.0.101"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e90cde112c4b9690b8cbe810cba9ddd8bc1d7472e2cae317b69e9438c1cba7d2"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "unicode-ident",
+]
+
+[[package]]
+name = "thiserror"
+version = "1.0.37"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "10deb33631e3c9018b9baf9dcbbc4f737320d2b576bac10f6aefa048fa407e3e"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.37"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "982d17546b47146b28f7c22e3d08465f6b8903d0ea13c1660d9d84a6e7adcdbb"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "unicode-ident"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dcc811dc4066ac62f84f11307873c4850cb653bfa9b1719cee2bd2204a4bc5dd"
+
+[[package]]
+name = "version_check"
+version = "0.9.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
+
+[[package]]
+name = "wasm-bindgen"
+version = "0.2.83"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eaf9f5aceeec8be17c128b2e93e031fb8a4d469bb9c4ae2d7dc1888b26887268"
+dependencies = [
+ "cfg-if",
+ "wasm-bindgen-macro",
+]
+
+[[package]]
+name = "wasm-bindgen-backend"
+version = "0.2.83"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c8ffb332579b0557b52d268b91feab8df3615f265d5270fec2a8c95b17c1142"
+dependencies = [
+ "bumpalo",
+ "log",
+ "once_cell",
+ "proc-macro2",
+ "quote",
+ "syn",
+ "wasm-bindgen-shared",
+]
+
+[[package]]
+name = "wasm-bindgen-futures"
+version = "0.4.33"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "23639446165ca5a5de86ae1d8896b737ae80319560fbaa4c2887b7da6e7ebd7d"
+dependencies = [
+ "cfg-if",
+ "js-sys",
+ "wasm-bindgen",
+ "web-sys",
+]
+
+[[package]]
+name = "wasm-bindgen-macro"
+version = "0.2.83"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "052be0f94026e6cbc75cdefc9bae13fd6052cdcaf532fa6c45e7ae33a1e6c810"
+dependencies = [
+ "quote",
+ "wasm-bindgen-macro-support",
+]
+
+[[package]]
+name = "wasm-bindgen-macro-support"
+version = "0.2.83"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "07bc0c051dc5f23e307b13285f9d75df86bfdf816c5721e573dec1f9b8aa193c"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+ "wasm-bindgen-backend",
+ "wasm-bindgen-shared",
+]
+
+[[package]]
+name = "wasm-bindgen-shared"
+version = "0.2.83"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1c38c045535d93ec4f0b4defec448e4291638ee608530863b1e2ba115d4fff7f"
+
+[[package]]
+name = "web-sys"
+version = "0.3.60"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bcda906d8be16e728fd5adc5b729afad4e444e106ab28cd1c7256e54fa61510f"
+dependencies = [
+ "js-sys",
+ "wasm-bindgen",
+]
+
+[[package]]
+name = "yew"
+version = "0.19.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2a1ccb53e57d3f7d847338cf5758befa811cabe207df07f543c06f502f9998cd"
+dependencies = [
+ "console_error_panic_hook",
+ "gloo",
+ "gloo-utils",
+ "indexmap",
+ "js-sys",
+ "scoped-tls-hkt",
+ "slab",
+ "wasm-bindgen",
+ "wasm-bindgen-futures",
+ "web-sys",
+ "yew-macro",
+]
+
+[[package]]
+name = "yew-macro"
+version = "0.19.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5fab79082b556d768d6e21811869c761893f0450e1d550a67892b9bce303b7bb"
+dependencies = [
+ "boolinator",
+ "lazy_static",
+ "proc-macro-error",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
diff --git a/corp/russian/predlozhnik/Cargo.toml b/corp/russian/predlozhnik/Cargo.toml
new file mode 100644
index 0000000000..90205bc4fb
--- /dev/null
+++ b/corp/russian/predlozhnik/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "predlozhnik"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+maplit = "1.0"
+lazy_static = "1.4"
+yew = "0.19"
+
+# needs to be in sync with nixpkgs
+wasm-bindgen = "= 0.2.83"
diff --git a/corp/russian/predlozhnik/default.nix b/corp/russian/predlozhnik/default.nix
new file mode 100644
index 0000000000..2137be1112
--- /dev/null
+++ b/corp/russian/predlozhnik/default.nix
@@ -0,0 +1,52 @@
+{ lib, pkgs, ... }:
+
+let
+  wasmRust = pkgs.rust-bin.stable.latest.default.override {
+    targets = [ "wasm32-unknown-unknown" ];
+  };
+
+  cargoToml = with builtins; fromTOML (readFile ./Cargo.toml);
+
+  wasmBindgenMatch =
+    cargoToml.dependencies.wasm-bindgen == "= ${pkgs.wasm-bindgen-cli.version}";
+
+  assertWasmBindgen = assert (lib.assertMsg wasmBindgenMatch ''
+    Due to instability in the Rust WASM ecosystem, the trunk build
+    tool enforces that the Cargo-dependency version of `wasm-bindgen`
+    MUST match the version of the CLI supplied in the environment.
+
+    This can get out of sync when nixpkgs is updated. To resolve it,
+    wasm-bindgen must be bumped in the Cargo.toml file and cargo needs
+    to be run to resolve the dependencies.
+
+    Versions of `wasm-bindgen` in Cargo.toml:
+
+      Expected: '= ${pkgs.wasm-bindgen-cli.version}'
+      Actual:   '${cargoToml.dependencies.wasm-bindgen}'
+  ''); pkgs.wasm-bindgen-cli;
+
+  deps = with pkgs; [
+    binaryen
+    sass
+    wasmRust
+    trunk
+    assertWasmBindgen
+  ];
+
+in
+pkgs.rustPlatform.buildRustPackage rec {
+  pname = "predlozhnik";
+  version = "canon";
+  src = lib.cleanSource ./.;
+  cargoLock.lockFile = ./Cargo.lock;
+
+  buildPhase = ''
+    export PATH=${lib.makeBinPath deps}:$PATH
+    mkdir home
+    export HOME=$PWD/.home
+    env
+    trunk build --release -d $out
+  '';
+
+  dontInstall = true;
+}
diff --git a/corp/russian/predlozhnik/index.css b/corp/russian/predlozhnik/index.css
new file mode 100644
index 0000000000..3529574c4f
--- /dev/null
+++ b/corp/russian/predlozhnik/index.css
@@ -0,0 +1,29 @@
+body {
+    max-width: 800px;
+    margin: 40px auto;
+}
+
+#header {
+    display: flex;
+    flex-direction: column;
+}
+
+.btn.btn-ghost:disabled {
+    border-color: #9f9f9f;
+    color: #9f9f9f;
+}
+
+#predlogi,#padezhi {
+    display: flex;
+    flex-direction: row;
+    flex-wrap: wrap;
+}
+
+.btn {
+    margin: 3px;
+    flex-grow: 1;
+}
+
+.footer {
+    text-align: right;
+}
diff --git a/corp/russian/predlozhnik/index.html b/corp/russian/predlozhnik/index.html
new file mode 100644
index 0000000000..6af1adc0bf
--- /dev/null
+++ b/corp/russian/predlozhnik/index.html
@@ -0,0 +1,24 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <link rel="stylesheet"
+          href="https://unpkg.com/terminal.css@0.7.2/dist/terminal.min.css" />
+    <link data-trunk rel="inline" href="index.css">
+    <title>Предложник</title>
+
+    <!-- Yandex.RTB -->
+    <script>window.yaContextCb=window.yaContextCb||[]</script>
+    <script src="https://yandex.ru/ads/system/context.js" async></script>
+  </head>
+  <body>
+    <noscript>
+      <h1>Предложник</h1>
+      <p>
+        ... показывает с какими падежами употребляются предлоги в
+        русском языке. Но, к сожалению, только с помощью Javascript.
+      </p>
+    </noscript>
+  </body>
+</html>
diff --git a/corp/russian/predlozhnik/src/main.rs b/corp/russian/predlozhnik/src/main.rs
new file mode 100644
index 0000000000..e267c849de
--- /dev/null
+++ b/corp/russian/predlozhnik/src/main.rs
@@ -0,0 +1,345 @@
+use yew::html::Scope;
+use yew::prelude::*;
+
+use lazy_static::lazy_static;
+use maplit::hashmap;
+use std::collections::BTreeSet;
+use std::collections::HashMap;
+
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
+enum Падеж {
+    Именительный,
+    Родительный,
+    Дательный,
+    Винительный,
+    Творительный,
+    Предложный,
+}
+
+impl Падеж {
+    const ВСЕ: [Self; 6] = [
+        Self::Именительный,
+        Self::Родительный,
+        Self::Дательный,
+        Self::Винительный,
+        Self::Творительный,
+        Self::Предложный,
+    ];
+
+    fn вопрос(&self) -> &str {
+        use Падеж::*;
+        match self {
+            Именительный => "кто? Что?",
+            Родительный => "кого? Чего?",
+            Дательный => "кому? Чему?",
+            Винительный => "кого? Что?",
+            Творительный => "кем? Чем?",
+            Предложный => "ком? Чём?",
+        }
+    }
+}
+
+lazy_static! {
+    static ref ПО_ПРЕДЛОГУ: HashMap<&'static str, BTreeSet<Падеж>> = {
+        use Падеж::*;
+
+        hashmap! {
+            "без" => BTreeSet::from([Родительный]),
+            "близ" => BTreeSet::from([Родительный]),
+            "в" => BTreeSet::from([Винительный, Предложный]),
+            "вместо" => BTreeSet::from([Родительный]),
+            "вне" => BTreeSet::from([Родительный]),
+            "внутри" => BTreeSet::from([Родительный]),
+            "возле" => BTreeSet::from([Родительный]),
+            "вокруг" => BTreeSet::from([Родительный]),
+            "вроде" => BTreeSet::from([Родительный]),
+            "для" => BTreeSet::from([Родительный]),
+            "до" => BTreeSet::from([Родительный]),
+            "за" => BTreeSet::from([Винительный, Творительный]),
+            "из" => BTreeSet::from([Родительный]),
+            "из-за" => BTreeSet::from([Родительный]),
+            "из-под" => BTreeSet::from([Родительный]),
+            "к" => BTreeSet::from([Дательный]),
+            "кроме" => BTreeSet::from([Родительный]),
+            "между" => BTreeSet::from([Творительный, Родительный]),
+            "на" => BTreeSet::from([Винительный, Предложный]),
+            "над" => BTreeSet::from([Творительный]),
+            "нет" => BTreeSet::from([Родительный]),
+            "о" => BTreeSet::from([Винительный, Предложный]),
+            "около" => BTreeSet::from([Родительный]),
+            "от" => BTreeSet::from([Родительный]),
+            "перед" => BTreeSet::from([Творительный]),
+            "по" => BTreeSet::from([Винительный, Дательный, Предложный]),
+            "под" => BTreeSet::from([Винительный, Творительный]),
+            "после" => BTreeSet::from([Родительный]),
+            "при" => BTreeSet::from([Предложный]),
+            "про" => BTreeSet::from([Винительный]),
+            "ради" => BTreeSet::from([Родительный]),
+            "с" => BTreeSet::from([Родительный, Винительный, Творительный]),
+            "сквозь" => BTreeSet::from([Винительный]),
+            "среди" => BTreeSet::from([Родительный]),
+            "у" => BTreeSet::from([Родительный]),
+            "через" => BTreeSet::from([Винительный]),
+        }
+    };
+    static ref ПО_ПАДЕЖУ: HashMap<Падеж, BTreeSet<&'static str>> = {
+        let mut m = hashmap!();
+
+        for c in Падеж::ВСЕ {
+            let mut предлоги: BTreeSet<&'static str> = BTreeSet::new();
+            for (k, v) in &*ПО_ПРЕДЛОГУ {
+                if v.contains(&c) {
+                    предлоги.insert(k);
+                }
+            }
+
+            m.insert(c, предлоги);
+        }
+
+        m
+    };
+    static ref ПАДЕЖИ: BTreeSet<Падеж> = BTreeSet::from(Падеж::ВСЕ);
+    static ref ПРЕДЛОГИ: BTreeSet<&'static str> = {
+        let mut s: BTreeSet<&'static str> = BTreeSet::new();
+
+        for п in ПО_ПРЕДЛОГУ.keys() {
+            s.insert(п);
+        }
+
+        s
+    };
+}
+
+fn исключение(предлог: &str, падеж: Падеж) -> Option<Html> {
+    use Падеж::*;
+
+    match (предлог, падеж) {
+        ("в", Винительный) => Some(html! {"Во что? В кого?"}),
+
+        ("о", Винительный) => Some(html! {
+            <>
+              <p>{"О кого? Обо что?"}</p>
+              <p>{"Редко используется. Например:"}</p>
+              <ul>
+                <li>{"Удариться о притолоку."}</li>
+                <li>{"точить о камень."}</li>
+              </ul>
+            </>
+        }),
+
+        ("между", Родительный) => Some(html! {
+            <>
+              <p>{"Между чего?"}</p>
+              <p>{"Редко используется. Только в идиомах и старой литературе:"}</p>
+              <ul>
+                <li>{"Читаю между строк."}</li>
+              </ul>
+            </>
+        }),
+
+        _ => None,
+    }
+}
+
+enum Сообщение {
+    ВыбралПадеж(Option<Падеж>),
+    ВыбралПредлог(Option<&'static str>),
+}
+
+#[derive(Default)]
+struct Модель {
+    падеж: Option<Падеж>,
+    предлог: Option<&'static str>,
+}
+
+struct Вывод {
+    доступные_падежи: BTreeSet<Падеж>,
+    доступные_предлоги: BTreeSet<&'static str>,
+    объяснение: Option<Html>,
+}
+
+fn объясни(падеж: Падеж, предлог: &str) -> Html {
+    let иск = match исключение(предлог, падеж) {
+        Some(exp) => html! { exp },
+        None => html! { format!("{} {}", предлог, падеж.вопрос()) },
+    };
+
+    html! {
+        <div id="obyasnenie">
+          <hr/>
+          <h2>{"Пример:"}</h2>
+          {иск}
+        </div>
+    }
+}
+
+fn ограничить(м: &Модель) -> Вывод {
+    match (м.падеж, &м.предлог) {
+        (Some(пж), Some(пл)) => Вывод {
+            доступные_падежи: (*ПО_ПРЕДЛОГУ)[пл].clone(),
+            доступные_предлоги: (*ПО_ПАДЕЖУ)[&пж].clone(),
+            объяснение: Some(объясни(пж, пл)),
+        },
+
+        (Some(пж), None) => Вывод {
+            доступные_падежи: BTreeSet::from([пж]),
+            доступные_предлоги: (*ПО_ПАДЕЖУ)[&пж].clone(),
+            объяснение: None,
+        },
+
+        (None, Some(пл)) => Вывод {
+            доступные_падежи: (*ПО_ПРЕДЛОГУ)[пл].clone(),
+            доступные_предлоги: BTreeSet::from([*пл]),
+            объяснение: None,
+        },
+
+        (None, None) => Вывод {
+            доступные_падежи: ПАДЕЖИ.clone(),
+            доступные_предлоги: ПРЕДЛОГИ.clone(),
+            объяснение: None,
+        },
+    }
+}
+
+fn класс_кнопки(выбран: bool, доступен: bool) -> String {
+    let класс = "btn ".to_string();
+    класс
+        + match (выбран, доступен) {
+            (true, _) => "btn-primary",
+            (false, true) => "btn-ghost btn-primary",
+            (false, false) => "btn-ghost btn-default",
+        }
+}
+
+fn покажи_предлог(
+    link: &Scope<Модель>,
+    м: &Модель,
+    вв: &Вывод,
+    п: &'static str,
+) -> Html {
+    let выбран = м.предлог == Some(п);
+    let доступен = вв.доступные_предлоги.contains(п);
+    let класс = класс_кнопки(выбран, доступен);
+
+    html! {
+        <button class={класс}
+         onclick={link.callback(move |_| if выбран {
+             Сообщение::ВыбралПредлог(None)
+         } else {
+             Сообщение::ВыбралПредлог(Some(п))
+         })}
+         disabled={!доступен}>
+        {п}
+        </button>
+    }
+}
+
+fn покажи_падеж(
+    link: &Scope<Модель>, м: &Модель, вв: &Вывод, п: Падеж
+) -> Html {
+    let выбран = м.падеж == Some(п);
+    let доступен = вв.доступные_падежи.contains(&п);
+    let класс = класс_кнопки(выбран, доступен);
+
+    html! {
+        <button class={класс}
+         onclick={link.callback(move |_| if выбран {
+             Сообщение::ВыбралПадеж(None)
+         } else {
+             Сообщение::ВыбралПадеж(Some(п))
+         })}
+         disabled={!доступен}>
+        {format!("{:?}", п)}
+        </button>
+    }
+}
+
+impl Component for Модель {
+    type Message = Сообщение;
+    type Properties = ();
+
+    fn create(_ctx: &Context<Self>) -> Self {
+        Default::default()
+    }
+
+    fn update(&mut self, _ctx: &Context<Self>, msg: Self::Message) -> bool {
+        match msg {
+            Сообщение::ВыбралПадеж(пж) => self.падеж = пж,
+            Сообщение::ВыбралПредлог(пл) => self.предлог = пл,
+        }
+
+        true
+    }
+
+    fn view(&self, ctx: &Context<Self>) -> Html {
+        let вв = ограничить(self);
+        let link = ctx.link();
+
+        let кнопки_предлогов = ПРЕДЛОГИ
+            .iter()
+            .map(|п| покажи_предлог(link, self, &вв, п))
+            .collect::<Html>();
+
+        let кнопки_падежов = ПАДЕЖИ
+            .iter()
+            .map(|п| покажи_падеж(link, self, &вв, *п))
+            .collect::<Html>();
+
+        let объяснение = вв.объяснение.map(|exp| exp).unwrap_or_else(|| html! {});
+
+        let footer = html! {
+            <footer>
+              <hr/>
+              <p class="footer">
+                <a href="https://code.tvl.fyi/tree/users/tazjin/predlozhnik">{"код"}</a>
+                {" | "}
+                {"сделано "}<a href="https://tvl.su">{"ООО \"ТВЛ\""}</a>
+              </p>
+            </footer>
+        };
+
+        let код_рекламы = r#"
+window.yaContextCb.push(()=>{
+  Ya.Context.AdvManager.render({
+    renderTo: 'yandex_rtb_R-A-1773485-1',
+    blockId: 'R-A-1773485-1'
+  })
+})
+"#;
+
+        let реклама = html! {
+            <div id="ad">
+              <div id="yandex_rtb_R-A-1773485-1"></div>
+              <script>{код_рекламы}</script>
+            </div>
+        };
+
+        html! {
+            <>
+                <div id="header">
+                  <h1>{"Предложник"}</h1>
+                  <p>{"... показывает с какими падежами употребляются предлоги в русском языке."}</p>
+                </div>
+
+                <h2>{"Выбирай предлог:"}</h2>
+                <div id="predlogi">
+                  {кнопки_предлогов}
+                </div>
+                <hr/>
+
+                <h2>{"Выбирай падеж:"}</h2>
+                <div id="padezhi">
+                  {кнопки_падежов}
+                </div>
+
+                {объяснение}
+                {footer}
+                {реклама}
+            </>
+        }
+    }
+}
+
+fn main() {
+    yew::start_app::<Модель>();
+}