package common

import (
	"crypto/tls"
	"fmt"
	"log"
	"net/http"
	"strings"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/awserr"
	"github.com/aws/aws-sdk-go/aws/credentials"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/ec2"
	"github.com/aws/aws-sdk-go/service/ec2/ec2iface"
	cleanhttp "github.com/hashicorp/go-cleanhttp"
	commonhelper "github.com/hashicorp/packer/helper/common"
	"github.com/hashicorp/packer/template/interpolate"
)

// AccessConfig is for common configuration related to AWS access
type AccessConfig struct {
	AccessKey             string `mapstructure:"access_key"`
	CustomEndpointEc2     string `mapstructure:"custom_endpoint_ec2"`
	DecodeAuthZMessages   bool   `mapstructure:"decode_authorization_messages"`
	InsecureSkipTLSVerify bool   `mapstructure:"insecure_skip_tls_verify"`
	MFACode               string `mapstructure:"mfa_code"`
	ProfileName           string `mapstructure:"profile"`
	RawRegion             string `mapstructure:"region"`
	SecretKey             string `mapstructure:"secret_key"`
	SkipValidation        bool   `mapstructure:"skip_region_validation"`
	SkipMetadataApiCheck  bool   `mapstructure:"skip_metadata_api_check"`
	Token                 string `mapstructure:"token"`
	session               *session.Session

	getEC2Connection func() ec2iface.EC2API
}

// Config returns a valid aws.Config object for access to AWS services, or
// an error if the authentication and region couldn't be resolved
func (c *AccessConfig) Session() (*session.Session, error) {
	if c.session != nil {
		return c.session, nil
	}

	config := aws.NewConfig().WithCredentialsChainVerboseErrors(true)
	staticCreds := credentials.NewStaticCredentials(c.AccessKey, c.SecretKey, c.Token)
	if _, err := staticCreds.Get(); err != credentials.ErrStaticCredentialsEmpty {
		config.WithCredentials(staticCreds)
	}

	if c.RawRegion != "" {
		config = config.WithRegion(c.RawRegion)
	}

	if c.CustomEndpointEc2 != "" {
		config = config.WithEndpoint(c.CustomEndpointEc2)
	}

	if c.InsecureSkipTLSVerify {
		config := config.WithHTTPClient(cleanhttp.DefaultClient())
		transport := config.HTTPClient.Transport.(*http.Transport)
		transport.TLSClientConfig = &tls.Config{
			InsecureSkipVerify: true,
		}
	}

	opts := session.Options{
		SharedConfigState: session.SharedConfigEnable,
		Config:            *config,
	}

	if c.ProfileName != "" {
		opts.Profile = c.ProfileName
	}

	if c.MFACode != "" {
		opts.AssumeRoleTokenProvider = func() (string, error) {
			return c.MFACode, nil
		}
	}

	sess, err := session.NewSessionWithOptions(opts)
	if err != nil {
		return nil, err
	}
	log.Printf("Found region %s", *sess.Config.Region)
	c.session = sess

	cp, err := c.session.Config.Credentials.Get()
	if err != nil {
		if awsErr, ok := err.(awserr.Error); ok && awsErr.Code() == "NoCredentialProviders" {
			return nil, fmt.Errorf("No valid credential sources found for AWS Builder. " +
				"Please see https://www.packer.io/docs/builders/amazon.html#specifying-amazon-credentials " +
				"for more information on providing credentials for the AWS Builder.")
		} else {
			return nil, fmt.Errorf("Error loading credentials for AWS Provider: %s", err)
		}
	}
	log.Printf("[INFO] AWS Auth provider used: %q", cp.ProviderName)

	if c.DecodeAuthZMessages {
		DecodeAuthZMessages(c.session)
	}
	LogEnvOverrideWarnings()

	return c.session, nil
}

func (c *AccessConfig) SessionRegion() string {
	if c.session == nil {
		panic("access config session should be set.")
	}
	return aws.StringValue(c.session.Config.Region)
}

func (c *AccessConfig) IsGovCloud() bool {
	return strings.HasPrefix(c.SessionRegion(), "us-gov-")
}

func (c *AccessConfig) IsChinaCloud() bool {
	return strings.HasPrefix(c.SessionRegion(), "cn-")
}

func (c *AccessConfig) Prepare(ctx *interpolate.Context) []error {
	var errs []error

	if c.SkipMetadataApiCheck {
		log.Println("(WARN) skip_metadata_api_check ignored.")
	}
	// Either both access and secret key must be set or neither of them should
	// be.
	if (len(c.AccessKey) > 0) != (len(c.SecretKey) > 0) {
		errs = append(errs,
			fmt.Errorf("`access_key` and `secret_key` must both be either set or not set."))
	}

	return errs
}

func (c *AccessConfig) NewEC2Connection() (ec2iface.EC2API, error) {
	if c.getEC2Connection != nil {
		return c.getEC2Connection(), nil
	}
	sess, err := c.Session()
	if err != nil {
		return nil, err
	}

	ec2conn := ec2.New(sess, &aws.Config{
		HTTPClient: commonhelper.HttpClientWithEnvironmentProxy(),
	})

	return ec2conn, nil
}
