From beea7b0caf3e30f5db2ba19043c1770bf4693d43 Mon Sep 17 00:00:00 2001
From: Harshad Sharma <harshad@sharma.io>
Date: Tue, 14 May 2024 06:22:55 +0530
Subject: [PATCH] Add colorhash

---
 config/config.exs                  |  3 +-
 config/runtime.exs                 |  6 ++++
 freedive.env.sample                |  1 +
 lib/freedive/colorhash.ex          | 48 ++++++++++++++++++++++++++++++
 lib/freedive_web/live/home_live.ex | 39 ++++++++++++++++++------
 test/freedive/colorhash_test.exs   | 23 ++++++++++++++
 6 files changed, 110 insertions(+), 10 deletions(-)
 create mode 100644 lib/freedive/colorhash.ex
 create mode 100644 test/freedive/colorhash_test.exs

diff --git a/config/config.exs b/config/config.exs
index de5dca8..c8d6154 100644
--- a/config/config.exs
+++ b/config/config.exs
@@ -13,7 +13,8 @@ config :freedive,
 
 config :freedive,
   features: [
-    register_account: true
+    register_account: true,
+    colorhash: true
   ]
 
 # Configures the endpoint
diff --git a/config/runtime.exs b/config/runtime.exs
index 2c82427..9b46e51 100644
--- a/config/runtime.exs
+++ b/config/runtime.exs
@@ -18,6 +18,12 @@ if config_env() == :prod do
     config :freedive, :features, register_account: false
   end
 
+  # Colorhash feature is enabled by default.
+  # To disable, set the COLORHASH_ENABLE environment variable to "false".
+  if System.get_env("COLORHASH_ENABLE") == "false" do
+    config :freedive, :features, colorhash: false
+  end
+
   database_path =
     System.get_env("DATABASE_PATH") ||
       raise """
diff --git a/freedive.env.sample b/freedive.env.sample
index cff49b5..bf2e487 100644
--- a/freedive.env.sample
+++ b/freedive.env.sample
@@ -11,6 +11,7 @@ TLS_CERT_PATH="<%= @data_dir %>/tls.crt"
 
 # Features
 REGISTER_ACCOUNT_ENABLE="false"
+COLORHASH_ENABLE="true"
 
 # Phoenix
 PHX_SERVER=true
diff --git a/lib/freedive/colorhash.ex b/lib/freedive/colorhash.ex
new file mode 100644
index 0000000..da43237
--- /dev/null
+++ b/lib/freedive/colorhash.ex
@@ -0,0 +1,48 @@
+defmodule Freedive.Colorhash do
+  @moduledoc """
+  Given a string returns consistent HSL color.
+  """
+  alias Freedive.Features
+
+  @default_hsl {0, 0, 0}
+
+  def hsl(input, css: true) do
+    {hue, saturation, lightness} = hsl(input)
+    "hsl(#{hue}, #{saturation}%, #{lightness}%)"
+  end
+
+  def hsl(input) do
+    if Features.enabled?(:colorhash) do
+      input = String.downcase(input)
+      hash = :erlang.phash2(input, 2_147_483_647)
+
+      hue = calculate_hue(hash)
+      saturation = 80 + rem(hash, 21)
+      lightness = 30 + rem(hash, 31)
+
+      {hue, saturation, lightness}
+    else
+      @default_hsl
+    end
+  end
+
+  @doc """
+  Calculates hue avoiding low contrast colors.
+  """
+  def calculate_hue(hash) do
+    base_hue = rem(hash, 360)
+
+    # Ranges to exclude (yellow to light green, cyan)
+    excluded_ranges = [
+      # yellow
+      {50, 70},
+      # cyan
+      {175, 185},
+    ]
+
+    # Adjust the hue to skip over excluded ranges
+    Enum.reduce(excluded_ranges, base_hue, fn {start, stop}, acc_hue ->
+      if acc_hue >= start and acc_hue <= stop, do: stop + (acc_hue - start + 1), else: acc_hue
+    end)
+  end
+end
diff --git a/lib/freedive_web/live/home_live.ex b/lib/freedive_web/live/home_live.ex
index 612ddc6..feef2b7 100644
--- a/lib/freedive_web/live/home_live.ex
+++ b/lib/freedive_web/live/home_live.ex
@@ -1,5 +1,6 @@
 defmodule FreediveWeb.HomeLive do
   use FreediveWeb, :live_view
+  import Freedive.Colorhash
 
   def render(assigns) do
     ~H"""
@@ -14,11 +15,19 @@ defmodule FreediveWeb.HomeLive do
           <a>System</a>
         </.panel_tabs>
         <.panel_tabs is-hidden-tablet>
-          <a class="is-active"><Lucideicons.infinity aria-hidden="true" /></a>
-          <a><Lucideicons.binary aria-hidden="true" /></a>
-          <a><Lucideicons.hard_drive aria-hidden="true" /></a>
-          <a><Lucideicons.earth aria-hidden="true" /></a>
-          <a><Lucideicons.bot aria-hidden="true" /></a>
+          <a class="is-active">
+            <Lucideicons.infinity style={"color: #{hsl("all", css: true)}"} aria-hidden="true" />
+          </a>
+          <a>
+            <Lucideicons.binary style={"color: #{hsl("compute", css: true)}"} aria-hidden="true" />
+          </a>
+          <a>
+            <Lucideicons.hard_drive style={"color: #{hsl("storage", css: true)}"} aria-hidden="true" />
+          </a>
+          <a>
+            <Lucideicons.earth style={"color: #{hsl("network", css: true)}"} aria-hidden="true" />
+          </a>
+          <a><Lucideicons.bot style={"color: #{hsl("system", css: true)}"} aria-hidden="true" /></a>
         </.panel_tabs>
 
         <.panel_block>
@@ -37,25 +46,37 @@ defmodule FreediveWeb.HomeLive do
         </.panel_block>
         <.link patch={~p"/users/settings"} class="panel-block pt-1">
           <span class="panel-icon">
-            <Lucideicons.user_cog aria-hidden="true" />
+            <Lucideicons.user_cog
+              style={"color: #{hsl("account settings", css: true)}"}
+              aria-hidden="true"
+            />
           </span>
           <span class="mt-2 ml-2">Account settings</span>
         </.link>
         <.link patch={~p"/services"} class="panel-block pt-1">
           <span class="panel-icon">
-            <Lucideicons.puzzle aria-hidden="true" />
+            <Lucideicons.puzzle
+              style={"color: #{hsl("system services", css: true)}"}
+              aria-hidden="true"
+            />
           </span>
           <div class="mt-2 ml-2">System services</div>
         </.link>
         <.link patch={~p"/packages"} class="panel-block pt-1">
           <span class="panel-icon">
-            <Lucideicons.package aria-hidden="true" />
+            <Lucideicons.package
+              style={"color: #{hsl("system packages", css: true)}"}
+              aria-hidden="true"
+            />
           </span>
           <span class="mt-2 ml-2">System packages</span>
         </.link>
         <.link patch={~p"/updates"} class="panel-block pt-1">
           <span class="panel-icon">
-            <Lucideicons.hard_drive_download aria-hidden="true" />
+            <Lucideicons.hard_drive_download
+              style={"color: #{hsl("system software updates", css: true)}"}
+              aria-hidden="true"
+            />
           </span>
           <span class="mt-2 ml-2">System software updates</span>
         </.link>
diff --git a/test/freedive/colorhash_test.exs b/test/freedive/colorhash_test.exs
new file mode 100644
index 0000000..532e5ad
--- /dev/null
+++ b/test/freedive/colorhash_test.exs
@@ -0,0 +1,23 @@
+defmodule Freedive.ColorhashTest do
+  use ExUnit.Case
+
+  test "hsl" do
+    assert Freedive.Colorhash.hsl("foo") == {312, 80, 48}
+    assert Freedive.Colorhash.hsl("bar") == {38, 88, 38}
+    assert Freedive.Colorhash.hsl("baz") == {288, 95, 42}
+  end
+
+  test "hsl with css" do
+    assert Freedive.Colorhash.hsl("foo", css: true) == "hsl(312, 80%, 48%)"
+    assert Freedive.Colorhash.hsl("bar", css: true) == "hsl(38, 88%, 38%)"
+    assert Freedive.Colorhash.hsl("baz", css: true) == "hsl(288, 95%, 42%)"
+  end
+
+  test "hsl with disabled feature" do
+    Freedive.Features.disable(:colorhash)
+    assert Freedive.Colorhash.hsl("foo") == {0, 0, 0}
+    assert Freedive.Colorhash.hsl("bar") == {0, 0, 0}
+    assert Freedive.Colorhash.hsl("baz") == {0, 0, 0}
+    Freedive.Features.enable(:colorhash)
+  end
+end