package plugin

import (
	"context"
	"fmt"
	"strings"
	"time"

	"github.com/go-errors/errors"
	"github.com/hashicorp/vault/logical"
	"github.com/hashicorp/vault/logical/framework"
)

const (
	rolePath       = "roles"
	rolePrefix     = "roles/"
	roleStorageKey = "roles"

	roleCacheCleanup    = time.Second / 2
	roleCacheExpiration = time.Second
)

func (b *backend) invalidateRole(ctx context.Context, key string) {
	if strings.HasPrefix(key, rolePrefix) {
		roleName := key[len(rolePrefix):]
		b.roleCache.Delete(roleName)
	}
}

func (b *backend) pathListRoles() *framework.Path {
	return &framework.Path{
		Pattern: rolePrefix + "?$",

		Callbacks: map[logical.Operation]framework.OperationFunc{
			logical.ListOperation: b.roleListOperation,
		},

		HelpSynopsis:    pathListRolesHelpSyn,
		HelpDescription: pathListRolesHelpDesc,
	}
}

func (b *backend) pathRoles() *framework.Path {
	return &framework.Path{
		Pattern: rolePrefix + framework.GenericNameRegex("name"),
		Fields: map[string]*framework.FieldSchema{
			"name": {
				Type:        framework.TypeLowerCaseString,
				Description: "Name of the role",
			},
			"service_account_name": {
				Type:        framework.TypeString,
				Description: "The username/logon name for the service account with which this role will be associated.",
			},
			"ttl": {
				Type:        framework.TypeDurationSecond,
				Description: "In seconds, the default password time-to-live.",
			},
		},
		Callbacks: map[logical.Operation]framework.OperationFunc{
			logical.UpdateOperation: b.roleUpdateOperation,
			logical.ReadOperation:   b.roleReadOperation,
			logical.DeleteOperation: b.roleDeleteOperation,
		},
		HelpSynopsis:    roleHelpSynopsis,
		HelpDescription: roleHelpDescription,
	}
}

func (b *backend) readRole(ctx context.Context, storage logical.Storage, roleName string) (*backendRole, error) {
	// If it's cached, return it from there.
	roleIfc, found := b.roleCache.Get(roleName)
	if found {
		return roleIfc.(*backendRole), nil
	}

	// It's not, read it from storage.
	entry, err := storage.Get(ctx, roleStorageKey+"/"+roleName)
	if err != nil {
		return nil, err
	}
	if entry == nil {
		return nil, nil
	}

	role := &backendRole{}
	if err := entry.DecodeJSON(role); err != nil {
		return nil, err
	}

	// Always check when ActiveDirectory shows the password as last set on the fly.
	engineConf, err := b.readConfig(ctx, storage)
	if err != nil {
		return nil, err
	}
	if engineConf == nil {
		return nil, errors.New("the config is currently unset")
	}

	passwordLastSet, err := b.client.GetPasswordLastSet(engineConf.ADConf, role.ServiceAccountName)
	if err != nil {
		return nil, err
	}
	role.PasswordLastSet = passwordLastSet

	// Cache it.
	b.roleCache.SetDefault(roleName, role)
	return role, nil
}

func (b *backend) writeRole(ctx context.Context, storage logical.Storage, roleName string, role *backendRole) error {
	entry, err := logical.StorageEntryJSON(roleStorageKey+"/"+roleName, role)
	if err != nil {
		return err
	}
	if err := storage.Put(ctx, entry); err != nil {
		return err
	}
	b.roleCache.SetDefault(roleName, role)
	return nil
}

func (b *backend) roleUpdateOperation(ctx context.Context, req *logical.Request, fieldData *framework.FieldData) (*logical.Response, error) {
	// Get everything we need to construct the role.
	roleName := fieldData.Get("name").(string)

	engineConf, err := b.readConfig(ctx, req.Storage)
	if err != nil {
		return nil, err
	}
	if engineConf == nil {
		return nil, errors.New("the config is currently unset")
	}

	// Actually construct it.
	serviceAccountName, err := getServiceAccountName(fieldData)
	if err != nil {
		return nil, err
	}

	// verify service account exists
	_, err = b.client.Get(engineConf.ADConf, serviceAccountName)
	if err != nil {
		return nil, err
	}

	ttl, err := getValidatedTTL(engineConf.PasswordConf, fieldData)
	if err != nil {
		return nil, err
	}
	role := &backendRole{
		ServiceAccountName: serviceAccountName,
		TTL:                ttl,
	}

	// Was there already a role before that we're now overwriting? If so, let's carry forward the LastVaultRotation.
	oldRole, err := b.readRole(ctx, req.Storage, roleName)
	if err != nil {
		return nil, err
	} else {
		if oldRole != nil {
			role.LastVaultRotation = oldRole.LastVaultRotation
		}
	}

	// writeRole it to storage and the roleCache.
	if err := b.writeRole(ctx, req.Storage, roleName, role); err != nil {
		return nil, err
	}

	// Return a 204.
	return nil, nil
}

func (b *backend) roleReadOperation(ctx context.Context, req *logical.Request, fieldData *framework.FieldData) (*logical.Response, error) {
	roleName := fieldData.Get("name").(string)

	role, err := b.readRole(ctx, req.Storage, roleName)
	if err != nil {
		return nil, err
	}
	if role == nil {
		return nil, nil
	}

	return &logical.Response{
		Data: role.Map(),
	}, nil
}

func (b *backend) roleListOperation(ctx context.Context, req *logical.Request, _ *framework.FieldData) (*logical.Response, error) {
	keys, err := req.Storage.List(ctx, roleStorageKey+"/")
	if err != nil {
		return nil, err
	}
	return logical.ListResponse(keys), nil
}

func (b *backend) roleDeleteOperation(ctx context.Context, req *logical.Request, fieldData *framework.FieldData) (*logical.Response, error) {
	roleName := fieldData.Get("name").(string)

	if err := req.Storage.Delete(ctx, roleStorageKey+"/"+roleName); err != nil {
		return nil, err
	}

	b.roleCache.Delete(roleName)

	if err := b.deleteCred(ctx, req.Storage, roleName); err != nil {
		return nil, err
	}
	return nil, nil
}

func getServiceAccountName(fieldData *framework.FieldData) (string, error) {
	serviceAccountName := fieldData.Get("service_account_name").(string)
	if serviceAccountName == "" {
		return "", errors.New("\"service_account_name\" is required")
	}
	return serviceAccountName, nil
}

func getValidatedTTL(passwordConf *passwordConf, fieldData *framework.FieldData) (int, error) {
	ttl := fieldData.Get("ttl").(int)
	if ttl == 0 {
		ttl = passwordConf.TTL
	}
	if ttl > passwordConf.MaxTTL {
		return 0, fmt.Errorf("requested ttl of %d seconds is over the max ttl of %d seconds", ttl, passwordConf.MaxTTL)
	}
	if ttl < 0 {
		return 0, fmt.Errorf("ttl can't be negative")
	}
	return ttl, nil
}

const (
	roleHelpSynopsis = `
Manage roles to build links between Vault and Active Directory service accounts.
`
	roleHelpDescription = `
This endpoint allows you to read, write, and delete individual roles that are used for enabling password rotation.

Deleting a role will not disable its current password. It will delete the role's associated creds in Vault.
`

	pathListRolesHelpSyn = `
List the name of each role currently stored.
`
	pathListRolesHelpDesc = `
To learn which service accounts are being managed by Vault, list the role names using
this endpoint. Then read any individual role by name to learn more, like the name of
the service account it's associated with.
`
)
