# roles/thin-client/deployment/disko.nix
#
# BTRFS disk layout via Disko. Used by `nixos-anywhere` during provisioning.
# Q4 decisions: Standard persistent BTRFS, subvolumes @root and @home,
# zstd compression, snapper for / (NOT /home — privacy for multi-user).
#
# Apply during provisioning:
#   nixos-anywhere --flake .#AZ-TC-01 \
#     --disko disko-config ./roles/thin-client/deployment/disko.nix \
#     root@<target-ip>
#
# This module sets `disko.devices` so the config can be referenced both
# for partitioning (nixos-anywhere --disko) and for fstab generation.
{config, lib, ...}: let
  inherit (lib) mkIf mkOption types;
  cfg = config.az.tc;
in {
  options.az.tc.deployment = {
    diskDevice = mkOption {
      type = types.str;
      default = "/dev/sda";
      description = ''
        Target disk device for the BTRFS layout. Typically /dev/sda or
        /dev/nvme0n1. Override per-host in hosts/AZ-TC-NN/default.nix.
      '';
    };

    swapSizeGB = mkOption {
      type = types.int;
      default = 4;
      description = "Swap partition size in GB. Set 0 to disable swap.";
    };
  };

  config = mkIf cfg.enable {
    disko.devices = {
      disk.main = {
        type = "disk";
        device = config.az.tc.deployment.diskDevice;
        content = {
          type = "gpt";
          partitions = {
            ESP = {
              size = "512M";
              type = "EF00";
              content = {
                type = "filesystem";
                format = "vfat";
                mountpoint = "/boot";
                mountOptions = ["umask=0077"];
              };
            };
            swap = mkIf (config.az.tc.deployment.swapSizeGB > 0) {
              size = "${toString config.az.tc.deployment.swapSizeGB}G";
              content = {
                type = "swap";
                randomEncryption = true;
              };
            };
            root = {
              size = "100%";
              content = {
                type = "btrfs";
                extraArgs = ["-f"]; # force overwrite
                subvolumes = {
                  "@root" = {
                    mountpoint = "/";
                    mountOptions = ["compress=zstd" "noatime" "ssd"];
                  };
                  "@home" = {
                    mountpoint = "/home";
                    mountOptions = ["compress=zstd" "noatime" "ssd"];
                  };
                  "@nix" = {
                    mountpoint = "/nix";
                    mountOptions = ["compress=zstd" "noatime" "ssd"];
                  };
                  "@persist" = {
                    mountpoint = "/persist";
                    mountOptions = ["compress=zstd" "noatime" "ssd"];
                  };
                  "@snapshots" = {
                    mountpoint = "/.snapshots";
                    mountOptions = ["compress=zstd" "noatime" "ssd"];
                  };
                };
              };
            };
          };
        };
      };
    };
  };
}