package model

import (
	"encoding/json"
	"fmt"
	"io"

	"git.sr.ht/~sircmpwn/core-go/crypto"
)

// TODO: Add field to prevent cursor reuse across unrelated resources
type Cursor struct {
	Count  int    `json:"count"`
	Next   string `json:"next"`
	Search string `json:"search"`
}

func (cur *Cursor) UnmarshalGQL(v interface{}) error {
	enc, ok := v.(string)
	if !ok {
		return fmt.Errorf("cursor must be strings")
	}
	plain := crypto.DecryptWithoutExpiration([]byte(enc))
	if plain == nil {
		return fmt.Errorf("Invalid cursor")
	}
	err := json.Unmarshal(plain, cur)
	if err != nil {
		// This is guaranteed to be a programming error
		panic(err)
	}
	return nil
}

func (cur Cursor) MarshalGQL(w io.Writer) {
	data, err := json.Marshal(cur)
	if err != nil {
		panic(err)
	}
	w.Write([]byte("\""))
	w.Write(crypto.Encrypt(data))
	w.Write([]byte("\""))
}

func derefOrInt(i *int, d int) int {
	if i != nil {
		return *i
	}
	return d
}

func NewCursor(filter *Filter) *Cursor {
	if filter != nil {
		count := derefOrInt(filter.Count, 25)
		if count <= 0 {
			count = 25
		}
		return &Cursor{
			Next:   "",
			Count:  count,
			Search: "", // TODO
		}
	}
	return &Cursor{
		Count:  25,
		Next:   "",
		Search: "",
	}
}