Refactored installer into modular library structure with improved error handling and logging.

The changes include:
- Split monolithic script into lib/, config/, profiles/, and files/ directories
- Added error handling with cleanup on failure
- Added installation logging to /var/log/arch-install.log
- Added username validation

lib/core/validation.sh

@@ -0,0 +1,138 @@
+#!/bin/bash
+
+# Copyright 2026 Logan Fick
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# validation.sh - Input validation functions
+#
+# Validates user input (disks, usernames, menu selections) to prevent errors
+# during installation.
+
+# Validate that a disk exists
+# Arguments:
+#   $1 - disk path (e.g., /dev/sda)
+# Returns:
+#   0 if disk exists, 1 otherwise
+validate_disk_exists() {
+    local disk="$1"
+
+    if [ ! -b "$disk" ]; then
+        print_error "Disk '$disk' does not exist or is not a block device."
+        return 1
+    fi
+    return 0
+}
+
+# Validate that a disk is not mounted
+# Arguments:
+#   $1 - disk path
+# Returns:
+#   0 if not mounted, 1 if mounted
+validate_disk_not_mounted() {
+    local disk="$1"
+
+    if mount | grep -q "^${disk}"; then
+        print_error "Disk '$disk' appears to be mounted. Please unmount it first."
+        return 1
+    fi
+    return 0
+}
+
+# Validate that two disks are different (for RAID1)
+# Arguments:
+#   $1 - first disk path
+#   $2 - second disk path
+# Returns:
+#   0 if different, 1 if same
+validate_disks_different() {
+    local disk1="$1"
+    local disk2="$2"
+
+    if [ "$disk1" = "$disk2" ]; then
+        print_error "Both disks must be different. You entered the same disk twice."
+        return 1
+    fi
+    return 0
+}
+
+# Validate username format
+# Arguments:
+#   $1 - username
+# Returns:
+#   0 if valid, 1 otherwise
+validate_username() {
+    local username="$1"
+
+    # Check if empty
+    if [ -z "$username" ]; then
+        print_error "Username cannot be empty."
+        return 1
+    fi
+
+    # Check length (max 32 chars)
+    if [ ${#username} -gt 32 ]; then
+        print_error "Username must be 32 characters or less."
+        return 1
+    fi
+
+    # Check format (lowercase letters, digits, underscore, hyphen; must start with letter)
+    if ! [[ "$username" =~ ^[a-z][a-z0-9_-]*$ ]]; then
+        print_error "Username must start with a lowercase letter and contain only lowercase letters, digits, underscores, and hyphens."
+        return 1
+    fi
+
+    return 0
+}
+
+# Validate menu selection is in range
+# Arguments:
+#   $1 - selection
+#   $2 - minimum value
+#   $3 - maximum value
+# Returns:
+#   0 if valid, 1 otherwise
+validate_menu_selection() {
+    local selection="$1"
+    local min="$2"
+    local max="$3"
+
+    # Check if it's a number
+    if ! [[ "$selection" =~ ^[0-9]+$ ]]; then
+        print_error "Please enter a number between $min and $max."
+        return 1
+    fi
+
+    # Check range
+    if [ "$selection" -lt "$min" ] || [ "$selection" -gt "$max" ]; then
+        print_error "Please enter a number between $min and $max."
+        return 1
+    fi
+
+    return 0
+}
+
+# Validate password is not empty
+# Arguments:
+#   $1 - password
+# Returns:
+#   0 if valid, 1 otherwise
+validate_password_not_empty() {
+    local password="$1"
+
+    if [ -z "$password" ]; then
+        print_error "Password cannot be empty."
+        return 1
+    fi
+    return 0
+}