#!/usr/bin/env bash

# === Motivation ===
# Provide a stable filesystem base aligned with user intent.

# === Problem Statement ===
# The wrapper must format the root and boot partitions using the selected filesystem.

# === Scope ===
# In scope: filesystem options, defaults, and naming.
# Out of scope: exact formatting command flags.

# === Concepts ===
# Root filesystem: primary data store inside the encrypted container.
# Boot filesystem: unencrypted partition for firmware and bootloader data.

# === Decisions ===
# Default to btrfs with opt-in alternatives for users who want ext4.
# Ensure filesystem choices are explicit and confirmed before formatting.
# Use swap file instead of swap partition to keep layout simple and flexible.
# Swap file lives inside encrypted root for automatic encryption protection.
# Swap file size is chosen interactively based on system needs.
# For btrfs, swap file must reside on a No-COW directory to avoid corruption.
# For btrfs, create subvolumes for root, home, var, log, snapshots, and swap.

# === Alternatives Considered ===
# Automatic detection of best filesystem rejected to keep behavior predictable.
# Swap partition rejected because it requires either:
#   - Separate LUKS container (second passphrase at boot)
#   - Unencrypted swap (security risk: sensitive data in swap)
#   - LVM setup (out of scope for this wrapper)
# Swap partition also has fixed size, while swap file can be resized post-install.

# === Constraints ===
# Filesystem choice must be compatible with the initramfs and bootloader.
# Hibernation with swap file requires kernel >= 5.0 and resume_offset parameter.
# For btrfs swap files, COW must be disabled on the swap directory.

# === Open Questions ===
# How should we handle swap file creation - in this phase or defer to post-install?
# Should we support configurable filesystem options (compression, mount flags)?

# === Success Criteria ===
# Filesystems are prepared in the right places and match the chosen layout.
# Swap file is ready for activation and resides within encrypted root.

format_filesystems() {
  : "${ESP_PART:?ESP partition is required}"
  : "${CRYPT_NAME:?Crypt mapping name is required}"
  : "${FS_TYPE:?Filesystem type is required}"
  : "${ROOT_LABEL:?Root filesystem label is required}"
  : "${EFI_LABEL:?EFI filesystem label is required}"
  local root_device
  root_device="/dev/mapper/${CRYPT_NAME}"

  log_info "Formatting ESP on $ESP_PART"
  mkfs.vfat -F32 -n "$EFI_LABEL" "$ESP_PART"

  if [[ "$FS_TYPE" == "btrfs" ]]; then
    log_info "Formatting root as btrfs on $root_device"
    mkfs.btrfs -L "$ROOT_LABEL" "$root_device"

    log_info "Creating btrfs subvolumes"
    local temp_mount
    temp_mount="/tmp/void-wrapper-btrfs"
    mkdir -p "$temp_mount"
    mount "$root_device" "$temp_mount"
    btrfs subvolume create "$temp_mount/@"
    btrfs subvolume create "$temp_mount/@home"
    btrfs subvolume create "$temp_mount/@var"
    btrfs subvolume create "$temp_mount/@log"
    btrfs subvolume create "$temp_mount/@snapshots"
    btrfs subvolume create "$temp_mount/@swap"
    umount "$temp_mount"
    rmdir "$temp_mount"
  else
    log_info "Formatting root as ext4 on $root_device"
    mkfs.ext4 -L "$ROOT_LABEL" "$root_device"
  fi
}