# Per-agent web UI static tree: the shipped frontend dist, the
# operator-extendable `extraFiles` overlay, and the merged tree the
# harness serves via `HIVE_STATIC_DIR`.
{
  pkgs,
  lib,
  config,
  ...
}:
{
  options.hyperhive.frontend.dist = lib.mkOption {
    type = lib.types.package;
    default = config.hyperhive.packages.frontend;
    defaultText = lib.literalMD "`hyperhive.packages.frontend` (the flake's frontend dist)";
    description = ''
      The shipped frontend dist (built by `nix/packages/frontend.nix`).
      Output layout: `dashboard/` (used by hive-c0re on the host) and
      `agent/` (used here, layered with `extraFiles` below at
      activation time). Override to ship a fully custom per-agent SPA;
      the JSON contract (`/api/state`, `/events/stream`, the action
      endpoints) is the source of truth for any replacement.
    '';
  };

  options.hyperhive.frontend.mergedDist = lib.mkOption {
    type = lib.types.package;
    readOnly = true;
    description = ''
      Computed: the merged static tree consumed by the harness via
      `HIVE_STATIC_DIR`. Composed at evaluation time by copying
      `hyperhive.frontend.dist`'s `agent/` subdir as the base, then
      layering each `extraFiles` entry on top. Read-only — do not set directly.
    '';
  };

  options.hyperhive.frontend.extraFiles = lib.mkOption {
    type = lib.types.attrsOf (
      lib.types.submodule (
        { name, ... }:
        {
          options = {
            source = lib.mkOption {
              type = lib.types.path;
              description = ''
                Source file or directory to layer over the default
                agent dist. A path (relative to `agent.nix` or
                absolute) — nix copies its contents into the merged
                static tree.
              '';
            };
            target = lib.mkOption {
              # First char must be alphanumeric/underscore (rules out
              # leading `/`, leading `.`, leading `-`); inner chars
              # include `.` and `/` so nested layouts like
              # `"games/bitburner"` work. This is the shape check —
              # the `..`-segment traversal check is the assertion in
              # `config.assertions` below (regex alone can't reject
              # mid-path `..` segments without lookahead, which nix
              # POSIX regex doesn't support).
              type = lib.types.strMatching "^[A-Za-z0-9_][A-Za-z0-9_./-]*$";
              default = name;
              defaultText = lib.literalMD "the attribute name";
              description = ''
                Destination path within the merged static tree, used
                as both the served URL prefix (`/<target>/...`) and
                the on-disk layout in the merged derivation. Defaults
                to the attribute name. Use forward slashes for
                nested layouts (e.g. `"games/bitburner"`).

                Constrained shape: must start with an alphanumeric or
                `_`, and only contain alphanumerics, `_`, `.`, `/`,
                `-`. `..` segments are separately rejected at config
                eval time.
              '';
            };
          };
        }
      )
    );
    default = { };
    example = lib.literalExpression ''
      {
        bitburner = {
          source = ./bitburner-dist;
          # served at GET /bitburner/...
        };
      }
    '';
    description = ''
      Per-agent additions layered on top of the default frontend
      dist. Each entry copies its `source` into the served static
      tree under `target`. Useful for shipping a self-contained
      agent-specific surface alongside the standard agent UI (e.g.
      the bitburner agent's game page at `/bitburner/`).

      The default agent UI remains served at `/`; entries here only
      add new routes and never replace the default. Overwrite
      semantics are **hard-fail**: if `target` collides with an
      existing file or directory in the default dist (or with a
      prior entry's target), the `mergedDist` build aborts with
      `refusing to overwrite existing path '<target>' in the
      default dist`. To override a default file, fork the dist via
      `hyperhive.frontend.dist` instead — `extraFiles` is for
      pure additions.

      `target` must be a relative path inside the static dir. An
      assertion rejects leading `/` and `..` segments at config
      eval time (string-concat-into-paths safety, even though
      agent.nix goes through operator review before deploy).
    '';
  };

  config = {
    assertions = [
      # hyperhive.frontend.extraFiles[*].target is concatenated into
      # $out during the mergedDist build. The option's strMatching
      # type already rejects leading `/`, leading `.`, and the
      # weirder characters; this assertion catches mid-path `..`
      # segments (e.g. `foo/../etc/passwd`) that the type's regex
      # can't easily express without lookahead. agent.nix is
      # operator-reviewed, so this is belt-and-braces — but it's the
      # kind of mistake that's easy to make and hard to spot.
      {
        assertion = lib.all (entry: !(builtins.any (seg: seg == "..") (lib.splitString "/" entry.target))) (
          lib.attrValues config.hyperhive.frontend.extraFiles
        );
        message = ''
          hyperhive.frontend.extraFiles: `target` must not contain
          `..` path segments.
        '';
      }
    ];

    # Merged frontend static tree. Base = `${frontend.dist}/agent/`,
    # then each `extraFiles` entry is laid on top at its `target`
    # path. The runCommand derivation aborts on overwrite so a
    # filename collision with the default dist surfaces as a build
    # failure rather than a silent override (operator gets a clear
    # nix error rather than a confusing 404 / silent dist swap).
    hyperhive.frontend.mergedDist = pkgs.runCommand "hyperhive-agent-frontend-merged" { } (
      ''
        mkdir -p $out
        cp -r ${config.hyperhive.frontend.dist}/agent/. $out/
        chmod -R u+w $out
      ''
      + lib.concatMapStrings (entry: ''
        mkdir -p $(dirname $out/${entry.target})
        if [ -e $out/${entry.target} ]; then
          echo "hyperhive.frontend.extraFiles: refusing to overwrite existing path '${entry.target}' in the default dist" >&2
          exit 1
        fi
        cp -r ${entry.source} $out/${entry.target}
      '') (lib.attrValues config.hyperhive.frontend.extraFiles)
    );
  };
}