package form

import (
	"mime/multipart"
	"net/http"
	"net/url"

	"github.com/pkg/errors"
)

type ValidationErrors map[string]error

type Form struct {
	fields []*Field
	errors ValidationErrors
}

func (f *Form) Handle(r *http.Request) error {
	if err := r.ParseForm(); err != nil {
		return errors.WithStack(err)
	}

	if err := f.Parse(r.Form); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func (f *Form) HandleMultipart(r *http.Request, maxMemory int64) error {
	if err := r.ParseMultipartForm(maxMemory); err != nil {
		return errors.WithStack(err)
	}

	if err := f.ParseMultipart(r.MultipartForm); err != nil {
		return errors.WithStack(err)
	}

	return nil
}

func (f *Form) ParseMultipart(multi *multipart.Form) error {
	for _, f := range f.fields {
		name := f.Name()

		values, exists := multi.Value[name]
		if !exists {
			f.Del("value")
		} else {
			f.Set("value", values)
		}

		files, exists := multi.File[name]
		if !exists {
			f.Del("file")
		} else {
			f.Set("file", files)
		}
	}

	return nil
}

func (f *Form) Parse(values url.Values) error {
	for _, f := range f.fields {
		name := f.Name()
		if !values.Has(name) {
			f.Del("value")
			continue
		}

		value := values.Get(name)
		f.Set("value", value)
	}

	return nil
}

func (f *Form) Validate() ValidationErrors {
	var errs ValidationErrors

	for _, f := range f.fields {
		if err := f.Validate(); err != nil {
			if errs == nil {
				errs = make(ValidationErrors)
			}

			errs[f.Name()] = err
		}
	}

	f.errors = errs

	return errs
}

func (f *Form) Field(name string) *Field {
	for _, field := range f.fields {
		if field.Name() == name {
			return field
		}
	}

	return nil
}

func (f *Form) Error(name string) (ValidationError, bool) {
	err, exists := f.errors[name]
	if !exists {
		return nil, false
	}

	var validationErr ValidationError
	if errors.As(err, &validationErr) {
		return validationErr, true
	}

	return NewValidationError("Unexpected error"), true
}

func (f *Form) Extend(fields ...*Field) *Form {
	fields = append(f.fields, fields...)
	return New(fields...)
}

func New(fields ...*Field) *Form {
	return &Form{
		fields: fields,
		errors: make(ValidationErrors),
	}
}