// Copyright © 2017 Mikael Berthe <mikael@lilotux.net>

//

// Licensed under the MIT license.

// Please see the LICENSE file is this directory.

package printer

import (

	"encoding/json"

	"fmt"

	"io"

	"os"

	"reflect"

	"text/template"

	"github.com/McKael/madon"

)

// TemplatePrinter represents a Template printer

type TemplatePrinter struct {

	rawTemplate string

	template    *template.Template

}

// NewPrinterTemplate returns a Template ResourcePrinter

// For TemplatePrinter, the option parameter contains the template string.

func NewPrinterTemplate(option string) (*TemplatePrinter, error) {

	tmpl := option

	t, err := template.New("output").Parse(tmpl)

	if err != nil {

		return nil, err

	}

	return &TemplatePrinter{

		rawTemplate: tmpl,

		template:    t,

	}, nil

}

// PrintObj sends the object as text to the writer

// If the writer w is nil, standard output will be used.

func (p *TemplatePrinter) PrintObj(obj interface{}, w io.Writer, tmpl string) error {

	if w == nil {

		w = os.Stdout

	}

	if p.template == nil {

		return fmt.Errorf("template not built")

	}

	switch ot := obj.(type) { // I wish I knew a better way...

	case []madon.Account, []madon.Application, []madon.Attachment, []madon.Card,

		[]madon.Client, []madon.Context, []madon.Instance, []madon.Mention,

		[]madon.Notification, []madon.Relationship, []madon.Report,

		[]madon.Results, []madon.Status, []madon.StreamEvent, []madon.Tag:

		return p.templateForeach(ot, w)

	}

	return p.templatePrintSingleObj(obj, w)

}

func (p *TemplatePrinter) templatePrintSingleObj(obj interface{}, w io.Writer) error {

	// This code comes from Kubernetes.

	data, err := json.Marshal(obj)

	if err != nil {

		return err

	}

	out := map[string]interface{}{}

	if err := json.Unmarshal(data, &out); err != nil {

		return err

	}

	if err = p.safeExecute(w, out); err != nil {

		return fmt.Errorf("error executing template %q: %v", p.rawTemplate, err)

	}

	return nil

}

// safeExecute tries to execute the template, but catches panics and returns an error

// should the template engine panic.

// This code comes from Kubernetes.

func (p *TemplatePrinter) safeExecute(w io.Writer, obj interface{}) error {

	var panicErr error

	// Sorry for the double anonymous function. There's probably a clever way

	// to do this that has the defer'd func setting the value to be returned, but

	// that would be even less obvious.

	retErr := func() error {

		defer func() {

			if x := recover(); x != nil {

				panicErr = fmt.Errorf("caught panic: %+v", x)

			}

		}()

		return p.template.Execute(w, obj)

	}()

	if panicErr != nil {

		return panicErr

	}

	return retErr

}

func (p *TemplatePrinter) templateForeach(ol interface{}, w io.Writer) error {

	switch reflect.TypeOf(ol).Kind() {

	case reflect.Slice:

		s := reflect.ValueOf(ol)

		for i := 0; i < s.Len(); i++ {

			o := s.Index(i).Interface()

			if err := p.templatePrintSingleObj(o, w); err != nil {

				return err

			}

		}

	}

	return nil

}