#!/usr/bin/env bash

# Installs or updates ddd and its ddc/ddu/ddp/ddb shortcuts.
# Requirements: Bash 3.2 or newer, curl, and either shasum or sha256sum.

set -o pipefail

readonly DDD_VERSION='0.2.0'
readonly DDD_SHA256='831a522dd6cd814d6359803f1b4cfbee5549e0a89d96481ef962c0ca8846391e'
readonly DEFAULT_DDD_URL='https://diffdump.com/cli/ddd'
readonly PROFILE_START='# >>> diffdump CLI >>>'
readonly PROFILE_END='# <<< diffdump CLI <<<'

usage() {
  cat <<'EOF'
Usage: install [options]

Install or update ddd and the ddc, ddu, ddp, and ddb shortcuts.

Options:
  --bin-dir <directory>  Installation directory (default: ~/.local/bin)
  --profile <file>       Shell profile to update (detected from $SHELL)
  --source-url <url>     Override the ddd download URL
  --no-profile           Do not add the installation directory to PATH
  -h, --help             Show this help
EOF
}

fail() {
  printf 'diffdump installer: %s\n' "$*" >&2
  return 1
}

require_command() {
  command -v "$1" >/dev/null 2>&1 || {
    fail "Required command '$1' is not installed."
    return
  }
}

sha256_file() {
  local file=$1
  local output

  if command -v shasum >/dev/null 2>&1; then
    output=$(shasum -a 256 -- "$file") || return
    printf '%s\n' "${output%%[[:space:]]*}"
    return
  fi

  if command -v sha256sum >/dev/null 2>&1; then
    output=$(sha256sum -- "$file") || return
    printf '%s\n' "${output%%[[:space:]]*}"
    return
  fi

  fail "Checksum verification requires 'shasum' or 'sha256sum'."
}

profile_has_managed_block() {
  local profile=$1
  local line

  [[ -f "$profile" ]] || return 1
  while IFS= read -r line || [[ -n "$line" ]]; do
    [[ "$line" == "$PROFILE_START" ]] && return 0
  done <"$profile"
  return 1
}

profile_managed_path_matches() {
  local profile=$1
  local expected_line=$2
  local line
  local inside_block=false

  [[ -f "$profile" ]] || return 1
  while IFS= read -r line || [[ -n "$line" ]]; do
    if [[ "$line" == "$PROFILE_START" ]]; then
      inside_block=true
    elif [[ "$line" == "$PROFILE_END" ]]; then
      return 1
    elif [[ "$inside_block" == true && "$line" == "$expected_line" ]]; then
      return 0
    fi
  done <"$profile"
  return 1
}

default_profile() {
  local shell_name=${SHELL##*/}

  case "$shell_name" in
    zsh)
      printf '%s\n' "${ZDOTDIR:-$HOME}/.zshrc"
      ;;
    bash)
      case "${OSTYPE:-}" in
        darwin*)
          printf '%s\n' "$HOME/.bash_profile"
          ;;
        *)
          printf '%s\n' "$HOME/.bashrc"
          ;;
      esac
      ;;
    *)
      printf '%s\n' "$HOME/.profile"
      ;;
  esac
}

[[ -n "${HOME:-}" ]] || {
  fail 'HOME is not set; use --bin-dir and --profile from a normal user shell.'
  exit 1
}

bin_dir=${HOME}/.local/bin
profile_path=$(default_profile)
source_url=$DEFAULT_DDD_URL
configure_profile=true

while (( $# > 0 )); do
  case "$1" in
    --bin-dir)
      (( $# >= 2 )) || {
        fail "Option '$1' requires a directory."
        exit 1
      }
      bin_dir=$2
      shift 2
      ;;
    --profile)
      (( $# >= 2 )) || {
        fail "Option '$1' requires a file."
        exit 1
      }
      profile_path=$2
      shift 2
      ;;
    --source-url)
      (( $# >= 2 )) || {
        fail "Option '$1' requires a URL."
        exit 1
      }
      source_url=$2
      shift 2
      ;;
    --no-profile)
      configure_profile=false
      shift
      ;;
    -h|--help)
      usage
      exit
      ;;
    *)
      fail "Unknown option '$1'. Run with --help for usage."
      exit 1
      ;;
  esac
done

for required_command in curl chmod mkdir mktemp mv ln readlink rm; do
  require_command "$required_command" || exit
done

mkdir -p -- "$bin_dir" || exit
bin_dir=$(cd "$bin_dir" && pwd -P) || exit
case "$profile_path" in
  /*) ;;
  *) profile_path="${PWD}/${profile_path}" ;;
esac
target_path="${bin_dir}/ddd"
quoted_bin_dir=$(printf '%q' "$bin_dir") || exit
path_export_line="export PATH=${quoted_bin_dir}:\$PATH"
quoted_profile_path=$(printf '%q' "$profile_path") || exit

if [[ -d "$target_path" && ! -L "$target_path" ]]; then
  fail "Refusing to replace directory '$target_path'."
  exit 1
fi

for shortcut_name in ddc ddu ddp ddb; do
  shortcut_path="${bin_dir}/${shortcut_name}"
  if [[ -L "$shortcut_path" ]]; then
    shortcut_target=$(readlink "$shortcut_path") || exit
    if [[ "$shortcut_target" != ddd && "$shortcut_target" != "$target_path" ]]; then
      fail "Refusing to replace '$shortcut_path'; it points to '$shortcut_target'."
      exit 1
    fi
  elif [[ -e "$shortcut_path" ]]; then
    fail "Refusing to replace existing path '$shortcut_path'."
    exit 1
  fi
done

path_is_configured=false
case ":${PATH}:" in
  *":${bin_dir}:"*)
    path_is_configured=true
    ;;
esac

if [[ "$configure_profile" == true && "$path_is_configured" == false ]] &&
  profile_has_managed_block "$profile_path" &&
  ! profile_managed_path_matches "$profile_path" "$path_export_line"; then
  fail "The managed PATH block in '$profile_path' points to another directory."
  fail 'Update or remove that block before choosing a different --bin-dir.'
  exit 1
fi

download_path=$(mktemp "${bin_dir}/.ddd.XXXXXXXX") || exit
cleanup() {
  if [[ -n "$download_path" && -e "$download_path" ]]; then
    rm -f -- "$download_path"
  fi
}
trap cleanup EXIT
trap 'exit 130' INT
trap 'exit 143' HUP TERM

curl --fail --location --silent --show-error \
  --output "$download_path" "$source_url" || exit

actual_sha256=$(sha256_file "$download_path") || exit
if [[ "$actual_sha256" != "$DDD_SHA256" ]]; then
  fail "Checksum mismatch for ddd $DDD_VERSION."
  fail "Expected $DDD_SHA256 but downloaded $actual_sha256."
  exit 1
fi

action=Installed
[[ -e "$target_path" ]] && action=Updated
chmod 0755 "$download_path" || exit
mv -f -- "$download_path" "$target_path" || exit
download_path=''

for shortcut_name in ddc ddu ddp ddb; do
  shortcut_path="${bin_dir}/${shortcut_name}"
  [[ -L "$shortcut_path" ]] || ln -s ddd "$shortcut_path" || exit
done

profile_changed=false
if [[ "$configure_profile" == true && "$path_is_configured" == false ]]; then
  if ! profile_has_managed_block "$profile_path"; then
    mkdir -p -- "${profile_path%/*}" || exit
    if [[ -s "$profile_path" ]]; then
      printf '\n' >>"$profile_path" || exit
    fi
    {
      printf '%s\n' "$PROFILE_START"
      printf '%s\n' "$path_export_line"
      printf '%s\n' "$PROFILE_END"
    } >>"$profile_path" || exit
    profile_changed=true
  fi
fi

installed_version=$("$target_path" version) || exit
printf '%s\n' "$action $installed_version to $target_path"
printf '%s\n' 'Installed shortcuts: ddc, ddu, ddp, ddb'

if [[ "$profile_changed" == true ]]; then
  printf '%s\n' "Added $bin_dir to PATH in $profile_path"
  printf '%s\n' "Start a new shell or run: source $quoted_profile_path"
elif [[ "$path_is_configured" == false ]]; then
  if [[ "$configure_profile" == true ]]; then
    printf '%s\n' "Start a new shell or run: source $quoted_profile_path"
  else
    printf 'Add %s to PATH to use ddd from your shell.\n' "$bin_dir" >&2
  fi
fi