From 2a195ae35afd54600f9cb3e26821800c6c7f9524 Mon Sep 17 00:00:00 2001
From: Jonah Kruschke <jonah.kruschke@gmail.com>
Date: Mon, 3 Aug 2020 22:51:02 -0400
Subject: [PATCH] chore(installation): Refactor installation script

- Run "install.sh" through `shellcheck` and implement the suggested
  changes, bar one regarding the use of `ls`.
- Ensure the `git clone ...` operation is successful before continuing.
- Add more descriptive comments.
- Refactor and simplify code.
---
 install.sh | 253 +++++++++++++++++++++--------------------------------
 1 file changed, 101 insertions(+), 152 deletions(-)

diff --git a/install.sh b/install.sh
index f3b3f33d..dbab72fe 100755
--- a/install.sh
+++ b/install.sh
@@ -1,184 +1,133 @@
 #!/usr/bin/env bash
-set -euo pipefail
 
-echo "Let's get you set up with Rustlings!"
-
-echo "Checking requirements..."
-if [ -x "$(command -v git)" ]
-then
-    echo "SUCCESS: Git is installed"
-else
-    echo "ERROR: Git does not seem to be installed."
-    echo "Please download Git using your package manager or over https://git-scm.com/!"
-    exit 1
-fi
-
-if [ -x "$(command -v cc)" ]
-then
-    echo "SUCCESS: cc is installed"
-else
-    echo "ERROR: cc does not seem to be installed."
-    echo "Please download (g)cc using your package manager."
-    echo "OSX: xcode-select --install"
-    echo "Deb: sudo apt install gcc"
-    echo "Yum: sudo yum -y install gcc"
-    exit 1
-fi
-
-if [ -x "$(command -v rustup)" ]
-then
-    echo "SUCCESS: rustup is installed"
-else
-    echo "ERROR: rustup does not seem to be installed."
-    echo "Please download rustup using https://rustup.rs!"
-    exit 1
-fi
-
-if [ -x "$(command -v rustc)" ]
-then
-    echo "SUCCESS: Rust is installed"
-else
-    echo "ERROR: Rust does not seem to be installed."
-    echo "Please download Rust using rustup!"
-    exit 1
-fi
-
-if [ -x "$(command -v cargo)" ]
-then
-    echo "SUCCESS: Cargo is installed"
-else
-    echo "ERROR: Cargo does not seem to be installed."
-    echo "Please download Rust and Cargo using rustup!"
-    exit 1
-fi
-
-# Look up python installations, starting with 3 with a fallback of 2
-if [ -x "$(command -v python3)" ]
-then
-    PY="$(command -v python3)"
-elif [ -x "$(command -v python)" ]
-then
-    PY="$(command -v python)"
-elif [ -x "$(command -v python2)" ]
-then
-    PY="$(command -v python2)"
-else
-    echo "ERROR: No working python installation was found"
-    echo "Please install python and add it to the PATH variable"
-    exit 1
-fi
-
-# Function that compares two versions strings v1 and v2 given in arguments (e.g 1.31 and 1.33.0).
-# Returns 1 if v1 > v2, 0 if v1 == v2, 2 if v1 < v2.
-function vercomp() {
-    if [[ $1 == $2 ]]
-    then
-        return 0
-    fi
-    v1=( ${1//./ } )
-    v2=( ${2//./ } )
-    len1=${#v1[@]}
-    len2=${#v2[@]}
-    max_len=$len1
-    if [[ $max_len -lt $len2 ]]
-    then
-        max_len=$len2
-    fi
-
-    #pad right in short arr
-    if [[ len1 -gt len2 ]];
-    then
-        for ((i = len2; i < len1; i++));
-        do
-            v2[$i]=0
-        done
-    else
-        for ((i = len1; i < len2; i++));
-        do
-            v1[$i]=0
-        done
-    fi
-
-    for i in `seq 0 $max_len`
+# Compare two version strings, v1 and v2, passed as arguments (e.g 1.31 and
+# 1.33.0). Returns 1 if v1 > v2, 0 if v1 == v2, 2 if v1 < v2.
+compare_versions() {
+    [ "$1" == "$2" ] && return 0
+    declare -a v1=() v2=()
+    mapfile -d . -t v1 < <(echo "$1")
+    mapfile -d . -t v2 < <(echo "$2")
+    declare -ir max_len=$(( ${#v1[@]} > ${#v2[@]} ? ${#v1[@]} : ${#v2[@]} ))
+    for i in $(seq 0 "$max_len")
     do
-        # Fill empty fields with zeros in v1
-        if [ -z "${v1[$i]}" ]
-        then
-            v1[$i]=0
-        fi
-        # And in v2
-        if [ -z "${v2[$i]}" ]
-        then
-            v2[$i]=0
-        fi
-        if [ ${v1[$i]} -gt ${v2[$i]} ]
-        then
-            return 1
-        fi
-        if [ ${v1[$i]} -lt ${v2[$i]} ]
-        then
-            return 2
-        fi
+        # Fill empty fields with zeros.
+        [ -z "${v1[$i]}" ] && v1["$i"]=0
+        [ -z "${v2[$i]}" ] && v2["$i"]=0
+        # Compare the fields.
+        [ ${v1[$i]} -gt ${v2[$i]} ] && return 1
+        [ ${v1[$i]} -lt ${v2[$i]} ] && return 2
     done
     return 0
 }
 
-RustVersion=$(rustc --version | cut -d " " -f 2)
-MinRustVersion=1.56
-vercomp "$RustVersion" $MinRustVersion || ec=$?
-if [ ${ec:-0} -eq 2 ]
+# Return 0 if the argument represents a valid command on the machine, 1
+# otherwise.
+verify_dependency() {
+    declare -r package="$1"
+    if [ -x "$(command -v "$package")" ]
+    then
+        echo "SUCCESS: \`$package\` is installed."
+        return 0
+    else
+        echo "ERROR: \`$package\` does not seem to be installed." >&2
+        return 1
+    fi
+}
+
+# Main logic begins here
+declare Clippy Py RustVersion Version
+declare -r CargoBin="${CARGO_HOME:-$HOME/.cargo}/bin"
+
+echo "Let's get you set up with Rustlings!"
+
+# Verify that the required dependencies are installed.
+echo "Checking requirements..."
+for dependency in cargo cc curl git rustc
+do
+    verify_dependency "$dependency" || exit 1
+done
+# Search for a Python installation; start with 3 and fallback to 2 if required.
+if [ -x "$(command -v python3)" ]
 then
-    echo "ERROR: Rust version is too old: $RustVersion - needs at least $MinRustVersion"
-    echo "Please update Rust with 'rustup update'"
+    Py="$(command -v python3)"
+elif [ -x "$(command -v python)" ]
+then
+    Py="$(command -v python)"
+elif [ -x "$(command -v python2)" ]
+then
+    Py="$(command -v python2)"
+else
+    echo "ERROR: no working Python installation was found." >&2
+    echo "Please install Python and add it to the PATH variable." >&2
+    exit 1
+fi
+
+# Ensure the installed Rust compiler is sufficiently up-to-date.
+RustVersion=$(rustc --version | cut -d " " -f 2)
+compare_versions "$RustVersion" "$MinRustVersion"
+if [ $? -eq 2 ]
+then
+    echo "ERROR: Rust $RustVersion is too old; the minimum version is" \
+         "$MinRustVersion." >&2
+    echo "Please update Rust with \`rustup update\`." >&2
     exit 1
 else
-    echo "SUCCESS: Rust is up to date"
+    echo "SUCCESS: Rust is up to date."
 fi
 
-Path=${1:-rustlings/}
-echo "Cloning Rustlings at $Path..."
-git clone -q https://github.com/rust-lang/rustlings "$Path"
-
-cd "$Path"
-
-Version=$(curl -s https://api.github.com/repos/rust-lang/rustlings/releases/latest | ${PY} -c "import json,sys;obj=json.load(sys.stdin);print(obj['tag_name']);")
-CargoBin="${CARGO_HOME:-$HOME/.cargo}/bin"
-
-if [[ -z ${Version} ]]
+# Clone the Git repository.
+echo "Cloning Rustlings into '$Path'..."
+if git clone -q "https://github.com/rust-lang/rustlings" "$Path"
 then
-    echo "The latest tag version could not be fetched remotely."
-    echo "Using the local git repository..."
-    Version=$(ls -tr .git/refs/tags/ | tail -1)
-    if [[ -z ${Version}  ]]
+    cd "$Path" || exit 1
+else
+    echo "ERROR: failed to clone the Git repository into '$Path'." >&2
+    exit 1
+fi
+
+# Determine which version of Rustlings to install from the Git repository.
+Version=$(
+    curl -s https://api.github.com/repos/rust-lang/rustlings/releases/latest \
+    | "$Py" -c \
+            "import json,sys;obj=json.load(sys.stdin);print(obj['tag_name'])"
+)
+if [ -z "$Version" ]
+then
+    echo "The latest tag version could not be fetched remotely, using the" \
+         "local Git repository..."
+    Version=$(ls -t .git/refs/tags/ | head --lines=1)
+    if [ -z "$Version" ]
     then
-        echo "No valid tag version found"
-        echo "Rustlings will be installed using the main branch"
+        echo "No valid tag version was found; Rustlings will be installed" \
+             "from the main Git branch."
         Version="main"
     else
-        Version="tags/${Version}"
+        Version="tags/$Version"
     fi
 else
-    Version="tags/${Version}"
+    Version="tags/$Version"
 fi
 
+# Install the selected version of Rustlings.
 echo "Checking out version $Version..."
-git checkout -q ${Version}
-
-echo "Installing the 'rustlings' executable..."
+git checkout -q "$Version"
+echo "Installing the \`rustlings\` executable..."
 cargo install --force --path .
 
+# Verify that the Rustlings installation was successful.
 if ! [ -x "$(command -v rustlings)" ]
 then
-    echo "WARNING: Please check that you have '$CargoBin' in your PATH environment variable!"
+    echo "WARNING: Please ensure '$CargoBin' is in your PATH environment" \
+         "variable!"
 fi
 
-# Checking whether Clippy is installed.
-# Due to a bug in Cargo, this must be done with Rustup: https://github.com/rust-lang/rustup/issues/1514
-Clippy=$(rustup component list | grep "clippy" | grep "installed")
+# Ensure Clippy is installed (due to a bug in Cargo, this must be done with
+# Rustup: https://github.com/rust-lang/rustup/issues/1514).
+Clippy=$(rustup component list | grep 'clippy.*(installed)')
 if [ -z "$Clippy" ]
 then
-    echo "Installing the 'cargo-clippy' executable..."
+    echo "Installing the \`cargo-clippy\` executable..."
     rustup component add clippy
 fi
 
-echo "All done! Run 'rustlings' to get started."
+echo "All done! Run \`rustlings\` to get started."