package engine

import (
	"context"
	"errors"
	"fmt"

	"gitoa.ru/go-4devs/mime"
	"gitoa.ru/go-4devs/templating/loader"
	"gitoa.ru/go-4devs/templating/render"
)

var _ render.Engine = (*Engine)(nil)

var (
	ErrNotSupport = errors.New("not support")
	ErrDuplicate  = errors.New("duplicate")
	ErrNotFound   = errors.New("not found")
)

type (
	Option func(*Engine)
	Parse  func(loader.Source) (Template, error)
)

type Cache interface {
	Set(ctx context.Context, tpl Template) error
	Get(ctx context.Context, name string) (Template, error)
	List(_ context.Context) []Template
}

func WithTemplates(tpls ...Template) Option {
	ctx := context.Background()

	return func(l *Engine) {
		for _, tpl := range tpls {
			_ = l.tpls.Set(ctx, tpl)
		}
	}
}

func WithLoader(load loader.Loader) Option {
	return func(l *Engine) {
		l.load = load
	}
}

func WithFormats(formats ...mime.Ext) Option {
	return func(e *Engine) {
		e.formats = formats
	}
}

func New(name string, parse Parse, opts ...Option) *Engine {
	engine := Engine{
		name:  name,
		parce: parse,
		tpls:  NewTemplates(),
		load:  loader.Empty(),
	}

	for _, opt := range opts {
		opt(&engine)
	}

	return &engine
}

type Engine struct {
	name    string
	formats []mime.Ext
	tpls    Cache
	load    loader.Loader
	parce   Parse
}

func (l Engine) WithLoader(load loader.Loader) *Engine {
	return New(l.name, l.parce, WithTemplates(l.tpls.List(context.Background())...), WithLoader(load))
}

func (l Engine) Add(ctx context.Context, tpls ...Template) error {
	for idx, tpl := range tpls {
		if err := l.tpls.Set(ctx, tpl); err != nil {
			return fmt.Errorf("engine add template[%d] with name %s: %w", idx, tpl.Name(), err)
		}
	}

	return nil
}

func (l Engine) Support(ctx context.Context, tpl render.Reference) bool {
	return Support(tpl, l.name, l.formats...)
}

func (l Engine) Load(ctx context.Context, reference render.Reference) (render.Execute, error) {
	var (
		tpl Template
		err error
	)

	tpl, err = l.tpls.Get(ctx, reference.Name())
	if err == nil {
		return tpl.Execute, nil
	}

	if !errors.Is(err, ErrNotFound) {
		return nil, fmt.Errorf("load get:%w", err)
	}

	source, err := l.load.Load(ctx, reference)
	if err != nil {
		return nil, fmt.Errorf("load source:%w", err)
	}

	tpl, err = l.parce(source)
	if err != nil {
		return nil, fmt.Errorf("load parce:%w", err)
	}

	if err := l.tpls.Set(ctx, tpl); err != nil {
		return nil, fmt.Errorf("load set:%w", err)
	}

	return tpl.Execute, nil
}