Configuration validation

Validate the Kamal configuration giving useful warning on errors.
Each section of the configuration has its own config class and a YAML
file containing documented example configuration.

You can run `kamal docs` to see the example configuration, and
`kamal docs <section>` to see the example configuration for a specific
section.

The validation matches the configuration to the example configuration
checking that there are no unknown keys and that the values are of
matching types.

Where there is more complex validation - e.g for envs and servers, we
have custom validators that implement those rules.

Additonally the configuration examples are used to generate the
configuration documentation in the kamal-site repo.

You generate them by running:

```
bundle exec bin/docs <kamal-site-checkout>
```

lib/kamal/configuration/role.rb

@@ -1,13 +1,33 @@
 class Kamal::Configuration::Role
+  include Kamal::Configuration::Validation
+
   CORD_FILE = "cord"
   delegate :argumentize, :optionize, to: Kamal::Utils
 
-  attr_accessor :name
+  attr_reader :name, :config, :specialized_env, :specialized_logging, :specialized_healthcheck
+
   alias to_s name
 
   def initialize(name, config:)
     @name, @config = name.inquiry, config
-    @tagged_hosts ||= extract_tagged_hosts_from_config
+    validate! \
+      specializations,
+      example: validation_yml["servers"]["workers"],
+      context: "servers/#{name}",
+      with: Kamal::Configuration::Validator::Role
+
+    @specialized_env = Kamal::Configuration::Env.new \
+      config: specializations.fetch("env", {}),
+      secrets_file: File.join(config.host_env_directory, "roles", "#{container_prefix}.env"),
+      context: "servers/#{name}/env"
+
+    @specialized_logging = Kamal::Configuration::Logging.new \
+      logging_config: specializations.fetch("logging", {}),
+      context: "servers/#{name}/logging"
+
+    @specialized_healthcheck = Kamal::Configuration::Healthcheck.new \
+      healthcheck_config: specializations.fetch("healthcheck", {}),
+      context: "servers/#{name}/healthcheck"
   end
 
   def primary_host
@@ -43,21 +63,17 @@ class Kamal::Configuration::Role
   end
 
   def logging_args
-    args = config.logging || {}
-    args.deep_merge!(specializations["logging"]) if specializations["logging"].present?
+    logging.args
+  end
 
-    if args.any?
-      optionize({ "log-driver" => args["driver"] }.compact) +
-        argumentize("--log-opt", args["options"])
-    else
-      config.logging_args
-    end
+  def logging
+    @logging ||= config.logging.merge(specialized_logging)
   end
 
 
   def env(host)
     @envs ||= {}
-    @envs[host] ||= [ base_env, specialized_env, *env_tags(host).map(&:env) ].reduce(:merge)
+    @envs[host] ||= [ config.env, specialized_env, *env_tags(host).map(&:env) ].reduce(:merge)
   end
 
   def env_args(host)
@@ -70,28 +86,29 @@ class Kamal::Configuration::Role
 
 
   def health_check_args(cord: true)
-    if health_check_cmd.present?
+    if running_traefik? || healthcheck.set_port_or_path?
       if cord && uses_cord?
-        optionize({ "health-cmd" => health_check_cmd_with_cord, "health-interval" => health_check_interval })
+        optionize({ "health-cmd" => health_check_cmd_with_cord, "health-interval" => healthcheck.interval })
           .concat(cord_volume.docker_args)
       else
-        optionize({ "health-cmd" => health_check_cmd, "health-interval" => health_check_interval })
+        optionize({ "health-cmd" => healthcheck.cmd, "health-interval" => healthcheck.interval })
       end
     else
       []
     end
   end
 
-  def health_check_cmd
-    health_check_options["cmd"] || http_health_check(port: health_check_options["port"], path: health_check_options["path"])
+  def healthcheck
+    @healthcheck ||=
+      if running_traefik?
+        config.healthcheck.merge(specialized_healthcheck)
+      else
+        specialized_healthcheck
+      end
   end
 
   def health_check_cmd_with_cord
-    "(#{health_check_cmd}) && (stat #{cord_container_file} > /dev/null || exit 1)"
-  end
-
-  def health_check_interval
-    health_check_options["interval"] || "1s"
+    "(#{healthcheck.cmd}) && (stat #{cord_container_file} > /dev/null || exit 1)"
   end
 
 
@@ -109,7 +126,7 @@ class Kamal::Configuration::Role
 
 
   def uses_cord?
-    running_traefik? && cord_volume && health_check_cmd.present?
+    running_traefik? && cord_volume && healthcheck.cmd.present?
   end
 
   def cord_host_directory
@@ -117,7 +134,7 @@ class Kamal::Configuration::Role
   end
 
   def cord_volume
-    if (cord = health_check_options["cord"])
+    if (cord = healthcheck.cord)
       @cord_volume ||= Kamal::Configuration::Volume.new \
         host_path: File.join(config.run_directory, "cords", [ container_prefix, config.run_id ].join("-")),
         container_path: cord
@@ -170,30 +187,24 @@ class Kamal::Configuration::Role
   end
 
   private
-    attr_accessor :config, :tagged_hosts
-
-    def extract_tagged_hosts_from_config
+    def tagged_hosts
       {}.tap do |tagged_hosts|
         extract_hosts_from_config.map do |host_config|
           if host_config.is_a?(Hash)
-            raise ArgumentError, "Multiple hosts found: #{host_config.inspect}" unless host_config.size == 1
-
             host, tags = host_config.first
             tagged_hosts[host] = Array(tags)
-          elsif host_config.is_a?(String) || host_config.is_a?(Symbol)
+          elsif host_config.is_a?(String)
             tagged_hosts[host_config] = []
-          else
-            raise ArgumentError, "Invalid host config: #{host_config.inspect}"
           end
         end
       end
     end
 
     def extract_hosts_from_config
-      if config.servers.is_a?(Array)
-        config.servers
+      if config.raw_config.servers.is_a?(Array)
+        config.raw_config.servers
       else
-        servers = config.servers[name]
+        servers = config.raw_config.servers[name]
         servers.is_a?(Array) ? servers : Array(servers["hosts"])
       end
     end
@@ -202,6 +213,14 @@ class Kamal::Configuration::Role
       { "service" => config.service, "role" => name, "destination" => config.destination }
     end
 
+    def specializations
+      if config.raw_config.servers.is_a?(Array) || config.raw_config.servers[name].is_a?(Array)
+        {}
+      else
+        config.raw_config.servers[name]
+      end
+    end
+
     def traefik_labels
       if running_traefik?
         {
@@ -229,35 +248,4 @@ class Kamal::Configuration::Role
         labels.merge!(specializations["labels"]) if specializations["labels"].present?
       end
     end
-
-    def specializations
-      if config.servers.is_a?(Array) || config.servers[name].is_a?(Array)
-        {}
-      else
-        config.servers[name].except("hosts")
-      end
-    end
-
-    def specialized_env
-      Kamal::Configuration::Env.from_config config: specializations.fetch("env", {})
-    end
-
-    # Secrets are stored in an array, which won't merge by default, so have to do it by hand.
-    def base_env
-      Kamal::Configuration::Env.from_config \
-        config: config.env,
-        secrets_file: File.join(config.host_env_directory, "roles", "#{container_prefix}.env")
-    end
-
-    def http_health_check(port:, path:)
-      "curl -f #{URI.join("http://localhost:#{port}", path)} || exit 1" if path.present? || port.present?
-    end
-
-    def health_check_options
-      @health_check_options ||= begin
-        options = specializations["healthcheck"] || {}
-        options = config.healthcheck.merge(options) if running_traefik?
-        options
-      end
-    end
 end