feat(day01): initial monorepo using bazel with a rust example

.bazelversion

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+6.3.2

.github/workflows/test.yml

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+name: Test
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - main
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: bazelbuild/setup-bazelisk@v2
+      - uses: actions/cache@v3
+        with:
+          path: "~/.cache/bazel"
+          key: bazel
+      - run: bazel build //...
+      - run: bazel test //...

.gitignore

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+## IDE
+.idea
+
+## Bazel
+# Ignore all bazel-* symlinks. There is no full list since this can change
+# based on the name of the directory bazel is cloned into.
+/bazel-*
+
+# Directories for the Bazel IntelliJ plugin containing the generated
+# IntelliJ project files and plugin configuration. Seperate directories are
+# for the IntelliJ, Android Studio and CLion versions of the plugin.
+/.ijwb/
+/.aswb/
+/.clwb/
+
+## Rust
+# Generated by Cargo
+# will have compiled files and executables
+debug/
+target/
+
+# These are backup files generated by rustfmt
+**/*.rs.bk
+
+# MSVC Windows builds of rustc generate these, which store debugging information
+*.pdb

README.md

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+# 15-Day Coding Challenges
+
+| Day | Date       | Challenge                                                                                                      | Link                                      |
+|-----|------------|----------------------------------------------------------------------------------------------------------------|-------------------------------------------|
+| 01  | 3 Sep 2023 | Initialize this repository as a monorepo using Bazel for multi-language development, include a Rust program example and add a GitHub Action to test all the projects | [challenges/day-01](./challenges/day-01) |

WORKSPACE.bazel

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+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+# Loads the `rules_rust` repository rule
+# See https://github.com/bazelbuild/rules_rust/releases
+http_archive(
+    name = "rules_rust",
+    sha256 = "db89135f4d1eaa047b9f5518ba4037284b43fc87386d08c1d1fe91708e3730ae",
+    urls = ["https://github.com/bazelbuild/rules_rust/releases/download/0.27.0/rules_rust-v0.27.0.tar.gz"],
+)
+
+# Loads the `rules_rust_dependencies` and `rust_register_toolchains` function definitions
+load("@rules_rust//rust:repositories.bzl", "rules_rust_dependencies", "rust_register_toolchains")
+
+# Adds the necessary dependencies for the Rust rules
+rules_rust_dependencies()
+
+# Registers Rust toolchains with the given versions and editions
+rust_register_toolchains(
+    # Specifies the Rust edition to use for the registered toolchains
+    edition = "2021",
+    versions = ["1.72.0"],
+)

challenges/day-01/BUILD.bazel

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+# Loads the Rust rules and the `rust_binary` & `rust_test` function definitions
+load("@rules_rust//rust:defs.bzl", "rust_binary", "rust_test")
+
+# Declares a Rust binary target with the given name
+rust_binary(
+    name = "day_01",
+
+    # Specifies the source file for the binary
+    srcs = glob([
+        "src/**/*.rs",
+    ]),
+
+    # Specifies the Rust edition to use for this binary
+    edition = "2021",
+)
+
+# Declares a Rust test target with the given name
+rust_test(
+    name = "day_01_test",
+
+    # Uses the same crate name as the underlying “:day_01” crate
+    crate = ":day_01",
+
+    # Specifies the Rust edition to use for this test
+    edition = "2021",
+)

challenges/day-01/Cargo.toml

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+[package]
+name = "day-01"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

challenges/day-01/README.md

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+# Day 01
+
+## Challenge description
+
+Initialize this repository as a monorepo using Bazel for multi-language development, include a Rust program example and add a GitHub Action to test all the projects.
+
+- [x] Monorepo
+- [x] Bazel
+- [x] Rust program
+- [x] GitHub Action
+
+## Getting Started
+
+```bash
+bazel run //challenges/day-01:day_01
+bazel test //challenges/day-01:day_01_test
+```
+
+## References
+
+- Doc: [Bazelisk](https://github.com/bazelbuild/bazelisk/blob/master/README.md)
+- Doc: [Bazel Versions](https://bazel.build/release#support-matrix)
+- Doc: [GitHub Action - bazelbuild/setup-bazelisk](https://github.com/bazelbuild/setup-bazelisk)
+- API: [rust_binary](http://bazelbuild.github.io/rules_rust/flatten.html#rust_binary)
+- API: [rust_test](http://bazelbuild.github.io/rules_rust/flatten.html#rust_test)
+- Article: [kriscfoster/multi-language-bazel-monorepo](https://github.com/kriscfoster/multi-language-bazel-monorepo)
+- Article: [Bazel with Rust](https://earthly.dev/blog/bazel-with-rust/)
+- Article: [Building Rust Workspace with Bazel](https://www.tweag.io/blog/2023-07-27-building-rust-workspace-with-bazel/)

challenges/day-01/src/main.rs

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+mod substring;
+
+fn main() {
+    let s = "Hello, World!";
+
+    let substring = substring::find_substring(s, "World");
+    println!("substring: {:?}", substring);
+
+    let new_string = substring::replace_substring(s, "World", "Rust");
+    println!("New string: {}", new_string);
+}

challenges/day-01/src/substring.rs

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+pub fn find_substring<'a>(s: &'a str, substring: &str) -> Option<&'a str> {
+    s.find(substring).map(|index| &s[index..index + substring.len()])
+}
+
+pub fn replace_substring(s: &str, from: &str, to: &str) -> String {
+    s.replace(from, to)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{find_substring, replace_substring};
+
+    #[test]
+    fn test_find_substring() {
+        assert_eq!(find_substring("hello", "ll"), Some("ll"));
+        assert_eq!(find_substring("hello", "world"), None);
+    }
+
+    #[test]
+    fn test_replace_substring() {
+        assert_eq!(replace_substring("hello", "ll", "ww"), "hewwo");
+        assert_eq!(replace_substring("hello", "world", "ww"), "hello");
+    }
+}