#!/bin/bash

set -euo pipefail

readonly RELEASE_API="https://api.github.com/repos/alacritty/alacritty/releases/latest"
readonly APPLICATIONS_DIR="/Applications"
readonly APP_NAME="Alacritty.app"

temp_dir=""
mount_point=""

cleanup() {
    if [[ -n "$mount_point" && -d "$mount_point" ]]; then
        hdiutil detach "$mount_point" >/dev/null 2>&1 || true
    fi
    if [[ -n "$temp_dir" && -d "$temp_dir" ]]; then
        rm -rf "$temp_dir"
    fi
}

trap cleanup EXIT INT TERM

die() {
    echo "Alacritty update failed: $*" >&2
    exit 1
}

require_command() {
    command -v "$1" >/dev/null 2>&1 || die "required command not found: $1"
}

app_version() {
    /usr/libexec/PlistBuddy -c "Print :CFBundleShortVersionString" \
        "$1/Contents/Info.plist" 2>/dev/null || true
}

version_is_newer() {
    local left="${1%%-*}"
    local right="${2%%-*}"
    local left_major left_minor left_patch
    local right_major right_minor right_patch

    IFS=. read -r left_major left_minor left_patch <<< "$left"
    IFS=. read -r right_major right_minor right_patch <<< "$right"

    [[ "$left_major" =~ ^[0-9]+$ && "$left_minor" =~ ^[0-9]+$ && "$left_patch" =~ ^[0-9]+$ ]] || return 1
    [[ "$right_major" =~ ^[0-9]+$ && "$right_minor" =~ ^[0-9]+$ && "$right_patch" =~ ^[0-9]+$ ]] || return 1

    (( 10#$left_major > 10#$right_major )) && return 0
    (( 10#$left_major < 10#$right_major )) && return 1
    (( 10#$left_minor > 10#$right_minor )) && return 0
    (( 10#$left_minor < 10#$right_minor )) && return 1
    (( 10#$left_patch > 10#$right_patch ))
}

run_for_applications() {
    if [[ -w "$APPLICATIONS_DIR" ]]; then
        "$@"
    else
        sudo "$@"
    fi
}

safe_link() {
    local source="$1"
    local destination="$2"

    if [[ -e "$destination" && ! -L "$destination" ]]; then
        die "will not replace non-symlink: $destination"
    fi
    ln -sfn "$source" "$destination"
}

assert_linkable() {
    local destination="$1"

    if [[ -e "$destination" && ! -L "$destination" ]]; then
        die "will not replace non-symlink: $destination"
    fi
}

validate_shell_artifacts() {
    local app="$1"
    local brew_prefix="$2"
    local resources="$app/Contents/Resources"
    local source manpage section

    for source in \
        "$app/Contents/MacOS/alacritty" \
        "$resources/completions/alacritty.bash" \
        "$resources/completions/alacritty.fish" \
        "$resources/completions/_alacritty" \
        "$resources/61/alacritty" \
        "$resources/61/alacritty-direct"; do
        [[ -f "$source" ]] || die "required artifact is missing: ${source#"$app/"}"
    done

    assert_linkable "$brew_prefix/bin/alacritty"
    assert_linkable "$brew_prefix/etc/bash_completion.d/alacritty"
    assert_linkable "$brew_prefix/share/fish/vendor_completions.d/alacritty.fish"
    assert_linkable "$brew_prefix/share/zsh/site-functions/_alacritty"
    assert_linkable "$HOME/.terminfo/61/alacritty"
    assert_linkable "$HOME/.terminfo/61/alacritty-direct"

    for section in 1 5 7; do
        for manpage in "$resources"/*."$section".gz; do
            [[ -e "$manpage" ]] || continue
            assert_linkable "$brew_prefix/share/man/man$section/${manpage##*/}"
        done
    done
}

install_shell_artifacts() {
    local app="$APPLICATIONS_DIR/$APP_NAME"
    local resources="$app/Contents/Resources"
    local brew_prefix="$1"
    local manpage section

    mkdir -p \
        "$brew_prefix/bin" \
        "$brew_prefix/etc/bash_completion.d" \
        "$brew_prefix/share/fish/vendor_completions.d" \
        "$brew_prefix/share/zsh/site-functions" \
        "$brew_prefix/share/man/man1" \
        "$brew_prefix/share/man/man5" \
        "$brew_prefix/share/man/man7" \
        "$HOME/.terminfo/61"

    safe_link "$app/Contents/MacOS/alacritty" "$brew_prefix/bin/alacritty"
    safe_link "$resources/completions/alacritty.bash" "$brew_prefix/etc/bash_completion.d/alacritty"
    safe_link "$resources/completions/alacritty.fish" "$brew_prefix/share/fish/vendor_completions.d/alacritty.fish"
    safe_link "$resources/completions/_alacritty" "$brew_prefix/share/zsh/site-functions/_alacritty"
    safe_link "$resources/61/alacritty" "$HOME/.terminfo/61/alacritty"
    safe_link "$resources/61/alacritty-direct" "$HOME/.terminfo/61/alacritty-direct"

    for section in 1 5 7; do
        for manpage in "$resources"/*."$section".gz; do
            [[ -e "$manpage" ]] || continue
            safe_link "$manpage" "$brew_prefix/share/man/man$section/${manpage##*/}"
        done
    done
}

restore_previous_app() {
    local destination="$1"
    local backup="$2"

    run_for_applications rm -rf "$destination"
    if [[ -d "$backup" ]]; then
        run_for_applications /usr/bin/ditto "$backup" "$destination"
    fi
}

main() {
    local destination="$APPLICATIONS_DIR/$APP_NAME"
    local release_json latest_tag latest_version asset_name asset_url asset_digest
    local expected_sha actual_sha dmg staged_app staged_version installed_version
    local previous_app brew_prefix brew_managed=false

    [[ "$(uname -s)" == "Darwin" ]] || die "this installer only supports macOS"

    require_command brew
    require_command curl
    require_command jq
    require_command hdiutil
    require_command codesign

    brew_prefix="$(brew --prefix)"
    if brew list --cask alacritty >/dev/null 2>&1; then
        brew_managed=true
    fi

    temp_dir="$(mktemp -d "${TMPDIR:-/tmp}/alacritty-update.XXXXXX")"
    release_json="$temp_dir/release.json"

    curl --fail --location --silent --show-error --retry 3 \
        -H "Accept: application/vnd.github+json" \
        -H "X-GitHub-Api-Version: 2022-11-28" \
        "$RELEASE_API" -o "$release_json"

    latest_tag="$(jq -er '.tag_name' "$release_json")"
    latest_version="${latest_tag#v}"
    asset_name="Alacritty-${latest_tag}.dmg"
    asset_url="$(jq -er --arg asset "$asset_name" \
        '.assets[] | select(.name == $asset) | .browser_download_url' "$release_json")"
    asset_digest="$(jq -er --arg asset "$asset_name" \
        '.assets[] | select(.name == $asset) | .digest' "$release_json")"

    [[ "$asset_digest" == sha256:* ]] || die "GitHub did not provide a SHA-256 digest for $asset_name"
    expected_sha="$(printf '%s' "${asset_digest#sha256:}" | tr '[:upper:]' '[:lower:]')"
    [[ "$expected_sha" =~ ^[[:xdigit:]]{64}$ ]] || die "invalid SHA-256 digest for $asset_name"

    installed_version=""
    if [[ -d "$destination" ]]; then
        installed_version="$(app_version "$destination")"
    fi

    if [[ "$installed_version" == "$latest_version" && "$brew_managed" == false ]]; then
        validate_shell_artifacts "$destination" "$brew_prefix"
        install_shell_artifacts "$brew_prefix"
        echo "Alacritty $installed_version is already up to date."
        return
    fi
    if [[ -n "$installed_version" ]] && version_is_newer "$installed_version" "$latest_version"; then
        echo "Installed Alacritty $installed_version is newer than stable $latest_version; leaving it unchanged."
        return
    fi

    echo "Installing Alacritty $latest_version from the upstream release."
    dmg="$temp_dir/$asset_name"
    curl --fail --location --silent --show-error --retry 3 "$asset_url" -o "$dmg"

    actual_sha="$(shasum -a 256 "$dmg" | awk '{print $1}')"
    [[ "$actual_sha" == "$expected_sha" ]] || die "SHA-256 mismatch for $asset_name"

    mount_point="$temp_dir/mount"
    mkdir -p "$mount_point"
    hdiutil attach "$dmg" -nobrowse -readonly -mountpoint "$mount_point" >/dev/null
    [[ -d "$mount_point/$APP_NAME" ]] || die "$APP_NAME is missing from $asset_name"

    staged_app="$temp_dir/$APP_NAME"
    /usr/bin/ditto "$mount_point/$APP_NAME" "$staged_app"
    hdiutil detach "$mount_point" >/dev/null
    mount_point=""

    staged_version="$(app_version "$staged_app")"
    [[ "$staged_version" == "$latest_version" ]] || die "release metadata says $latest_version, app says $staged_version"
    codesign --verify --deep --strict "$staged_app" || die "the staged app has an invalid ad-hoc signature"
    xattr -dr com.apple.quarantine "$staged_app" 2>/dev/null || true
    validate_shell_artifacts "$staged_app" "$brew_prefix"

    previous_app="$temp_dir/previous/$APP_NAME"
    if [[ -d "$destination" ]]; then
        mkdir -p "${previous_app%/*}"
        /usr/bin/ditto "$destination" "$previous_app"
    fi

    if [[ "$brew_managed" == true ]]; then
        echo "Migrating Alacritty away from the disabled Homebrew cask."
        if ! brew uninstall --cask alacritty; then
            restore_previous_app "$destination" "$previous_app"
            install_shell_artifacts "$brew_prefix" || true
            die "Homebrew could not uninstall its Alacritty cask"
        fi
    fi

    if ! run_for_applications rm -rf "$destination" || \
       ! run_for_applications /usr/bin/ditto "$staged_app" "$destination"; then
        restore_previous_app "$destination" "$previous_app"
        die "could not install $destination"
    fi

    if ! codesign --verify --deep --strict "$destination" || \
       [[ "$(app_version "$destination")" != "$latest_version" ]]; then
        restore_previous_app "$destination" "$previous_app"
        die "installed app validation failed; restored the previous app"
    fi

    install_shell_artifacts "$brew_prefix"
    echo "Alacritty $latest_version installed successfully."
}

if [[ "${BASH_SOURCE[0]}" == "$0" ]]; then
    main "$@"
fi