#!/usr/bin/env bash
set -euo pipefail

# Walnut CLI installer
# Usage: curl -fsSL https://walnut.sh | bash

RELEASES_URL="${WALNUT_RELEASES_URL:-https://releases.walnut.sh}"
VERSION="${WALNUT_VERSION:-latest}"
INSTALL_DIR="${WALNUT_INSTALL_DIR:-$HOME/.walnut}"
BIN_DIR="$INSTALL_DIR/bin"

tildify() {
  if [[ $1 == "$HOME"/* ]]; then
    echo "~${1#"$HOME"}"
  else
    echo "$1"
  fi
}

info() {
  printf '%s\n' "$@"
}

warn() {
  printf '%s\n' "$@" >&2
}

main() {
  local platform arch
  platform="$(uname -s | tr '[:upper:]' '[:lower:]')"
  arch="$(uname -m)"

  case "$arch" in
    x86_64)        arch="x64" ;;
    aarch64|arm64) arch="arm64" ;;
    *) warn "error: unsupported architecture: $arch" && exit 1 ;;
  esac

  case "$platform" in
    darwin|linux) ;;
    *) warn "error: unsupported platform: $platform" && exit 1 ;;
  esac

  local binary="walnut-${platform}-${arch}"
  local url="${RELEASES_URL}/${VERSION}/${binary}"

  info "Installing walnut ${VERSION} for ${platform}-${arch}..."
  info "  from: ${url}"

  mkdir -p "$BIN_DIR"

  if ! curl -fsSL "$url" -o "$BIN_DIR/walnut"; then
    echo ""
    warn "error: download failed. Check that version '${VERSION}' exists at:"
    warn "  ${RELEASES_URL}/${VERSION}/"
    exit 1
  fi

  chmod +x "$BIN_DIR/walnut"

  # Verify the binary runs.
  if ! "$BIN_DIR/walnut" version >/dev/null 2>&1; then
    warn "error: downloaded binary failed to execute. This may be a platform mismatch."
    rm -f "$BIN_DIR/walnut"
    exit 1
  fi

  local installed_version
  installed_version=$("$BIN_DIR/walnut" version 2>/dev/null || echo "unknown")

  info ""
  info "  ${installed_version}"
  info "  installed to ${BIN_DIR}/walnut"

  # -------------------------------------------------------------------------
  # Add to PATH: detect shell, append to rc file if not already present.
  # -------------------------------------------------------------------------
  if [[ ":$PATH:" == *":$BIN_DIR:"* ]]; then
    # Already on PATH — nothing to do.
    return
  fi

  local shell_name
  shell_name="$(basename "${SHELL:-bash}")"

  local refresh_command=""
  local rc_updated=false

  case "$shell_name" in
    fish)
      local fish_config="${XDG_CONFIG_HOME:-$HOME/.config}/fish/config.fish"
      if append_to_rc "$fish_config" \
        "# walnut" \
        "set --export WALNUT_INSTALL $(quote_for_shell "$INSTALL_DIR")" \
        "set --export PATH \$WALNUT_INSTALL/bin \$PATH"; then
        rc_updated=true
        refresh_command="source $(tildify "$fish_config")"
      fi
      ;;
    zsh)
      local zsh_config="$HOME/.zshrc"
      if append_to_rc "$zsh_config" \
        "# walnut" \
        "export WALNUT_INSTALL=$(quote_for_shell "$INSTALL_DIR")" \
        "export PATH=\"\$WALNUT_INSTALL/bin:\$PATH\""; then
        rc_updated=true
        refresh_command="exec $SHELL"
      fi
      ;;
    bash|*)
      # Try each bash config in order, use the first writable one.
      local bash_configs=()

      # Prefer .bash_profile on macOS (login shells), .bashrc on Linux.
      if [[ "$platform" == "darwin" ]]; then
        bash_configs+=("$HOME/.bash_profile" "$HOME/.bashrc")
      else
        bash_configs+=("$HOME/.bashrc" "$HOME/.bash_profile")
      fi

      if [[ -n "${XDG_CONFIG_HOME:-}" ]]; then
        bash_configs+=("$XDG_CONFIG_HOME/.bashrc" "$XDG_CONFIG_HOME/.bash_profile")
      fi

      local bash_config
      for bash_config in "${bash_configs[@]}"; do
        if append_to_rc "$bash_config" \
          "# walnut" \
          "export WALNUT_INSTALL=$(quote_for_shell "$INSTALL_DIR")" \
          "export PATH=\"\$WALNUT_INSTALL/bin:\$PATH\""; then
          rc_updated=true
          refresh_command="source $(tildify "$bash_config")"
          break
        fi
      done
      ;;
  esac

  if $rc_updated; then
    info ""
    info "Added $(tildify "$BIN_DIR") to \$PATH"
    info ""
    info "To start using walnut, run:"
    info ""
    info "  $refresh_command"
  else
    info ""
    info "Manually add walnut to your PATH:"
    info ""
    info "  export PATH=\"$(tildify "$BIN_DIR"):\$PATH\""
    info ""
    info "Add that line to your shell config to make it permanent."
  fi
}

# Append lines to an rc file if: (a) the file exists or can be created,
# (b) it's writable, and (c) it doesn't already contain a walnut PATH entry.
# Returns 0 (success) if lines were appended, 1 otherwise.
append_to_rc() {
  local rc_file="$1"
  shift
  local lines=("$@")

  # Create the file if it doesn't exist (e.g. fresh machine).
  if [[ ! -f "$rc_file" ]]; then
    local rc_dir
    rc_dir="$(dirname "$rc_file")"
    if [[ ! -d "$rc_dir" ]]; then
      mkdir -p "$rc_dir" 2>/dev/null || return 1
    fi
    touch "$rc_file" 2>/dev/null || return 1
  fi

  if [[ ! -w "$rc_file" ]]; then
    return 1
  fi

  # Don't duplicate if already present.
  if grep -q 'WALNUT_INSTALL' "$rc_file" 2>/dev/null; then
    return 0
  fi

  printf '\n' >> "$rc_file"
  for line in "${lines[@]}"; do
    printf '%s\n' "$line" >> "$rc_file"
  done

  return 0
}

# Quote a path for embedding in a shell config file.
quote_for_shell() {
  if [[ "$1" == "$HOME"/* ]]; then
    # Use $HOME reference so the config stays portable across machines.
    echo "\"\$HOME${1#"$HOME"}\""
  elif [[ "$1" == *" "* || "$1" == *"'"* ]]; then
    echo "\"$1\""
  else
    echo "$1"
  fi
}

main