#!/usr/bin/env bash
# 0009 — the mutation check.
#
# Copies your crate to a temp dir, plants ONE deliberate bug in the copy, and
# runs YOUR tests against it. Your own files are never touched.
#
#   killed   = your tests noticed the bug. Good.
#   SURVIVED = the bug is invisible to your suite. Write the missing test.
#   SKIP     = the pattern is not in your source, so nothing was planted.
#
# Usage:  bash 0009-mutants.sh ~/learn-rust/tasks

set -u
crate=$(cd "${1:-.}" && pwd)
work=$(mktemp -d)
export CARGO_TARGET_DIR=$work/target
killed=0 survived=0 skipped=0

# name <TAB> file <TAB> sed expression
mutants=$(cat <<'EOF'
stats-order	src/cli.rs	s/Priority::High, Priority::Medium, Priority::Low/Priority::Low, Priority::Medium, Priority::High/
stats-zero	src/cli.rs	s/unwrap_or(0)/unwrap_or(1)/
clear-count	src/cli.rs	s/remove_completed()/remove_completed() + 1/
list-format	src/task.rs	s/({})"/{}"/
status-parse	src/task.rs	s/"in-progress" =>/"inprogress" =>/
command-case	src/command.rs	s/to_lowercase()/to_string()/
EOF
)

echo "crate: $crate"
while IFS=$'\t' read -r name file expr; do
    d=$(mktemp -d)
    cp -r "$crate/src" "$crate/tests" "$crate/Cargo.toml" "$crate/Cargo.lock" "$d/"

    if [ ! -f "$d/$file" ]; then
        printf '  SKIP     %-13s %s does not exist yet\n' "$name" "$file"
        skipped=$((skipped + 1))
        continue
    fi

    before=$(md5sum <"$d/$file")
    sed -i "$expr" "$d/$file"
    if [ "$before" = "$(md5sum <"$d/$file")" ]; then
        printf '  SKIP     %-13s pattern not found in %s\n' "$name" "$file"
        skipped=$((skipped + 1))
        continue
    fi

    if ! (cd "$d" && cargo build --tests -q) >/dev/null 2>&1; then
        printf '  SKIP     %-13s mutant does not compile\n' "$name"
        skipped=$((skipped + 1))
        continue
    fi

    if (cd "$d" && cargo test -q) >/dev/null 2>&1; then
        printf '  SURVIVED %-13s %s\n' "$name" "$file"
        survived=$((survived + 1))
    else
        printf '  killed   %-13s %s\n' "$name" "$file"
        killed=$((killed + 1))
    fi
done <<<"$mutants"

printf '\n%d killed, %d survived, %d skipped\n' "$killed" "$survived" "$skipped"
[ "$survived" -eq 0 ]