package testutil

import (
	"context"
	"encoding/json"
	"time"

	"github.com/Khan/genqlient/graphql"
)

type ID string

type Pokemon struct {
	Species string `json:"species"`
	Level   int    `json:"level"`
}

func (p Pokemon) Battle(q Pokemon) bool {
	return p.Level > q.Level
}

type MyContext interface {
	context.Context

	MyMethod()
}

func GetClientFromNowhere() (graphql.Client, error)                    { return nil, nil }
func GetClientFromContext(ctx context.Context) (graphql.Client, error) { return nil, nil }
func GetClientFromMyContext(ctx MyContext) (graphql.Client, error)     { return nil, nil }

const dateFormat = "2006-01-02"

func MarshalDate(t *time.Time) ([]byte, error) {
	// nil should never happen but we might as well check.  zero-time does
	// happen because omitempty doesn't consider it zero; we'd prefer to write
	// null than "0001-01-01".
	//
	// (I mean, we're tests.  Who cares!  But we may as well try to match what
	// prod code would want.)
	if t == nil || t.IsZero() {
		return []byte("null"), nil
	}
	return []byte(`"` + t.Format(dateFormat) + `"`), nil
}

func UnmarshalDate(b []byte, t *time.Time) error {
	// (modified from time.Time.UnmarshalJSON)
	var err error
	*t, err = time.Parse(`"`+dateFormat+`"`, string(b))
	return err
}

type Option[V any] struct {
	value V
	ok    bool
}

func Some[V any](value V) Option[V] {
	return Option[V]{value: value, ok: true}
}

func None[V any]() Option[V] {
	return Option[V]{ok: false}
}

func (v Option[V]) Unpack() (V, bool) {
	return v.value, v.ok
}

func (v Option[V]) Get(fallback V) V {
	if v.ok {
		return v.value
	}

	return fallback
}

func FromPtr[V any](ptr *V) Option[V] {
	if ptr == nil {
		return None[V]()
	}

	return Some(*ptr)
}

func (value Option[V]) MarshalJSON() ([]byte, error) {
	if value.ok {
		return json.Marshal(value.value)
	} else {
		return json.Marshal((*V)(nil))
	}
}

func (value *Option[V]) UnmarshalJSON(data []byte) error {
	v := (*V)(nil)

	err := json.Unmarshal(data, &v)
	if err != nil {
		return err
	}

	if v != nil {
		value.value = *v
		value.ok = true
	}

	return nil
}