package context

import (
	"fmt"
	"io"
)

// ErrViewNotExist it's an error.
// It reports whether a template was not found in the parsed templates tree.
type ErrViewNotExist struct {
	Name     string
	IsLayout bool
	Data     interface{}
}

// Error completes the `error` interface.
func (e ErrViewNotExist) Error() string {
	title := "template"
	if e.IsLayout {
		title = "layout"
	}
	return fmt.Sprintf("%s '%s' does not exist", title, e.Name)
}

// ViewEngine is the interface which all view engines should be implemented in order to be registered inside iris.
type ViewEngine interface {
	// Name returns the name of the engine.
	Name() string
	// Load should load the templates from the given FileSystem.
	Load() error
	// ExecuteWriter should execute a template by its filename with an optional layout and bindingData.
	ExecuteWriter(w io.Writer, filename string, layout string, bindingData interface{}) error
	// Ext should return the final file extension (including the dot)
	// which this view engine is responsible to render.
	// If the filename extension on ExecuteWriter is empty then this is appended.
	Ext() string
}

// ViewEngineFuncer is an addition of a view engine,
// if a view engine implements that interface
// then iris can add some closed-relative iris functions
// like {{ url }}, {{ urlpath }} and {{ tr }}.
type ViewEngineFuncer interface {
	// AddFunc should adds a function to the template's function map.
	AddFunc(funcName string, funcBody interface{})
}