# Nomarchy theming engine.
#
# nomarchy.stateFile (theme-state.json, inside the consuming flake) is
# ingested at evaluation time — pure, because flake files are store
# paths — and exposed to every other module as `config.nomarchy.theme`.
#
# Theme changes are fully Home Manager managed: `nomarchy-theme-sync
# apply <theme>` writes the JSON and runs `home-manager switch`, baking
# everything (Hyprland, Waybar, Ghostty, btop, Stylix) into one
# read-only generation. No runtime patching, no partial states; theme
# history is generation history.
#
# The one runtime exception is the wallpaper (swww is imperative by
# nature): applied at session start, after every switch (hook below),
# and cycled instantly with `nomarchy-theme-sync bg next`.
{ config, lib, pkgs, ... }:

let
  cfg = config.nomarchy;

  themeState = builtins.fromJSON (builtins.readFile cfg.stateFile);

  # Defaults guarantee evaluation succeeds on a sparse or older state
  # file (e.g. one written before a schema field was added). The shipped
  # Tokyo Night preset provides the color/ansi fallbacks; the path is
  # relative to this module, so it resolves inside Nomarchy's own flake
  # source even when consumed downstream.
  preset = builtins.fromJSON (builtins.readFile ../../themes/tokyo-night.json);

  defaults = preset // {
    fonts = {
      mono = "JetBrainsMono Nerd Font";
      ui = "Inter";
      size = 11;
    };
    ui = {
      gapsIn = 5;
      gapsOut = 12;
      borderSize = 2;
      rounding = 10;
      activeOpacity = 1.0;
      inactiveOpacity = 0.95;
      terminalOpacity = 0.96;
      blur = true;
      shadow = true;
    };
    # Icon theme name; "" means "pick by mode" (resolved below). A preset
    # or the state file can name any theme in the shipped icon package.
    icons = "";
    # Window border colors. Values are palette keys (resolved against
    # `colors` below) or literal #rrggbb. Solid, not a gradient — every
    # legacy identity theme used a solid border (accent for most, the text
    # tone for kanagawa/summer-*). Each preset declares its own so a theme
    # switch always replaces it (deep_merge would otherwise leave it stuck).
    border = { active = "accent"; inactive = "overlay"; };
  };

  parsed = lib.recursiveUpdate defaults themeState;

  # A border value is a palette key (look it up in colors) unless it's
  # already a literal hex; unknown keys fall through to the raw string.
  resolveColor = v: if lib.hasPrefix "#" v then v else parsed.colors.${v} or v;
  border = {
    active = resolveColor parsed.border.active;
    inactive = resolveColor parsed.border.inactive;
  };

  # Resolve the icon theme once and expose it on nomarchy.theme so both
  # the GTK side (stylix.nix) and rofi (rofi.nix) agree. The shipped
  # package (papirus-icon-theme) carries the Dark/Light pair.
  iconTheme =
    if parsed.icons != "" then parsed.icons
    else if parsed.mode == "light" then "Papirus-Light"
    else "Papirus-Dark";
in
{
  config = {
    nomarchy.theme = parsed // { inherit iconTheme border; };

    nomarchy.lib = {
      # "#7aa2f7" -> "rgb(7aa2f7)"          (Hyprland color syntax)
      rgb = c: "rgb(${lib.removePrefix "#" c})";
      # "#16161e" -> "rgba(16161eaa)"       (Hyprland color + hex alpha)
      rgba = c: alpha: "rgba(${lib.removePrefix "#" c}${alpha})";
    };

    home.packages = [ cfg.package ];

    # After a switch the new theme's wallpaper should show without
    # logging out. Best-effort: outside a graphical session swww isn't
    # running and this is a no-op.
    home.activation.nomarchyWallpaper = lib.hm.dag.entryAfter [ "writeBoundary" ] ''
      run ${lib.getExe cfg.package} --quiet wallpaper || true
    '';
  };
}