#!/bin/sh

set -eu

error() {
    printf 'Error: %s\n' "$*" >&2
    exit 1
}

[ "$#" -eq 0 ] || error "this installer takes no arguments"
[ -n "${HOME:-}" ] || error "HOME is unset or empty"

for tool in uname curl mktemp awk sha256sum mkdir chmod mv cp rm; do
    command -v "$tool" >/dev/null 2>&1 || error "required tool not found: $tool"
done

[ "$(uname -s)" = "Linux" ] || error "unsupported operating system; EC supports Linux only"

case "$(uname -m)" in
    x86_64|amd64) asset=ec-linux-x86_64 ;;
    aarch64|arm64) asset=ec-linux-aarch64 ;;
    *) error "unsupported architecture: $(uname -m); expected x86_64 or aarch64" ;;
esac

base=https://github.com/luigiverona/ec/releases/latest/download
work=$(mktemp -d) || error "could not create a temporary directory"
stage=
cleanup() {
    [ -z "$stage" ] || rm -f "$stage"
    rm -rf "$work"
}
trap cleanup EXIT HUP INT TERM

binary="$work/$asset"
sums="$work/SHA256SUMS"
check="$work/check"

printf 'Downloading EC...\n'
curl --proto '=https' --tlsv1.2 -fL --retry 3 --retry-delay 1 --retry-max-time 20 \
    -o "$binary" "$base/$asset" || error "failed to download $asset"
curl --proto '=https' --tlsv1.2 -fL --retry 3 --retry-delay 1 --retry-max-time 20 \
    -o "$sums" "$base/SHA256SUMS" || error "failed to download SHA256SUMS"
[ -s "$binary" ] || error "downloaded binary is empty"
[ -s "$sums" ] || error "downloaded checksum file is empty"

awk -v name="$asset" '
    NF == 2 && $2 == name { count++; line = $0 }
    END { if (count != 1) exit 1; print line }
' "$sums" >"$check" || error "expected checksum is missing or duplicated"

printf 'Verifying checksum...\n'
(cd "$work" && sha256sum -c check >/dev/null) || error "checksum verification failed"

destination="$HOME/.local/bin"
mkdir -p "$destination" || error "could not create $destination"
stage=$(mktemp "$destination/.ec.XXXXXX") || error "could not create installation file"
cp "$binary" "$stage" || error "could not stage EC"
chmod 0755 "$stage" || error "could not set executable permissions"
mv -f "$stage" "$destination/ec" || error "could not install EC"
stage=

printf '\nEC installed.\n\nNext:\n  ec doctor\n  ec start\n'

case ":${PATH:-}:" in
    *:"$destination":*) ;;
    *) printf '\nAdd this directory to PATH:\n\n  %s\n' "$destination" ;;
esac