package step

import "html/template"

// Provider is an object which provides extra functionality to an environment.
type Provider interface {
	// Package returns the package identifier of the provider. For example:
	// git.tebibyte.media/sashakoshka/step/examples/testplugin. The only
	// exception is providers within the providers sub-package, which just
	// return their basename.
	Package () string
}

// Configurable is an object that can be configured according to metadata.
type Configurable interface {
	Provider
	// Configure uses config to configure the object. It must not modify
	// config. Keys are namespaced with a '.' and are written in kebab case.
	Configure (config Meta) error
}

// ConfigProcessor is an object that can alter the environment configuration
// before other providers are configured in order to provide a sort of macro
// system.
type ConfigProcessor interface {
	// ProcessConfig analyzes and makes necessary changes to config. Unlike
	// Configurable.Configure, it can modify config.
	ProcessConfig (config Meta) error
}

// Trimmer is an object that needs to be routinely "trimmed". This can be
// garbage collecting, sanity checking, etc.
type Trimmer interface {
	// Trim trims the object. It must not block for any significant length
	// of time. It should be called every minute or so.
	Trim ()
}

// Initializer is an object that must be initialized before first use.
type Initializer interface {
	Init () error
}

// FuncProvider provides a template.FuncMap.
type FuncProvider interface {
	Provider
	// FuncMap provides a template.FuncMap. It may return nil, in which case
	// its result is simply not considered.
	FuncMap () template.FuncMap
}

// FuncProviderFor is an object that provides a template.FuncMap for a specific
// document.
type FuncProviderFor interface {
	Provider
	// FuncMap provides a template.FuncMap, given a particular document. It
	// may return nil, in which case its result is simply not considered.
	FuncMapFor (*Document) template.FuncMap
}