package transit

import (
	"encoding/base64"
	"fmt"

	"github.com/hashicorp/vault/helper/errutil"
	"github.com/hashicorp/vault/logical"
	"github.com/hashicorp/vault/logical/framework"
)

func (b *backend) pathRewrap() *framework.Path {
	return &framework.Path{
		Pattern: "rewrap/" + framework.GenericNameRegex("name"),
		Fields: map[string]*framework.FieldSchema{
			"name": &framework.FieldSchema{
				Type:        framework.TypeString,
				Description: "Name of the key",
			},

			"ciphertext": &framework.FieldSchema{
				Type:        framework.TypeString,
				Description: "Ciphertext value to rewrap",
			},

			"context": &framework.FieldSchema{
				Type:        framework.TypeString,
				Description: "Context for key derivation. Required for derived keys.",
			},

			"nonce": &framework.FieldSchema{
				Type:        framework.TypeString,
				Description: "Nonce for when convergent encryption is used",
			},
		},

		Callbacks: map[logical.Operation]framework.OperationFunc{
			logical.UpdateOperation: b.pathRewrapWrite,
		},

		HelpSynopsis:    pathRewrapHelpSyn,
		HelpDescription: pathRewrapHelpDesc,
	}
}

func (b *backend) pathRewrapWrite(
	req *logical.Request, d *framework.FieldData) (*logical.Response, error) {
	name := d.Get("name").(string)

	value := d.Get("ciphertext").(string)
	if len(value) == 0 {
		return logical.ErrorResponse("missing ciphertext to decrypt"), logical.ErrInvalidRequest
	}

	var err error

	// Decode the context if any
	contextRaw := d.Get("context").(string)
	var context []byte
	if len(contextRaw) != 0 {
		context, err = base64.StdEncoding.DecodeString(contextRaw)
		if err != nil {
			return logical.ErrorResponse("failed to decode context as base64"), logical.ErrInvalidRequest
		}
	}

	// Decode the nonce if any
	nonceRaw := d.Get("nonce").(string)
	var nonce []byte
	if len(nonceRaw) != 0 {
		nonce, err = base64.StdEncoding.DecodeString(nonceRaw)
		if err != nil {
			return logical.ErrorResponse("failed to decode nonce as base64"), logical.ErrInvalidRequest
		}
	}

	// Get the policy
	p, lock, err := b.lm.GetPolicyShared(req.Storage, name)
	if lock != nil {
		defer lock.RUnlock()
	}
	if err != nil {
		return nil, err
	}
	// Error if invalid policy
	if p == nil {
		return logical.ErrorResponse("policy not found"), logical.ErrInvalidRequest
	}

	plaintext, err := p.Decrypt(context, nonce, value)
	if err != nil {
		switch err.(type) {
		case errutil.UserError:
			return logical.ErrorResponse(err.Error()), logical.ErrInvalidRequest
		case errutil.InternalError:
			return nil, err
		default:
			return nil, err
		}
	}

	if plaintext == "" {
		return nil, fmt.Errorf("empty plaintext returned during rewrap")
	}

	ciphertext, err := p.Encrypt(context, nonce, plaintext)
	if err != nil {
		switch err.(type) {
		case errutil.UserError:
			return logical.ErrorResponse(err.Error()), logical.ErrInvalidRequest
		case errutil.InternalError:
			return nil, err
		default:
			return nil, err
		}
	}

	if ciphertext == "" {
		return nil, fmt.Errorf("empty ciphertext returned")
	}

	// Generate the response
	resp := &logical.Response{
		Data: map[string]interface{}{
			"ciphertext": ciphertext,
		},
	}
	return resp, nil
}

const pathRewrapHelpSyn = `Rewrap ciphertext`

const pathRewrapHelpDesc = `
After key rotation, this function can be used to rewrap the
given ciphertext with the latest version of the named key.
If the given ciphertext is already using the latest version
of the key, this function is a no-op.
`