package imds

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"strings"
	"time"

	"github.com/aws/smithy-go"
	smithyio "github.com/aws/smithy-go/io"
	"github.com/aws/smithy-go/middleware"
	smithyhttp "github.com/aws/smithy-go/transport/http"
)

const getIAMInfoPath = getMetadataPath + "/iam/info"

// GetIAMInfo retrieves an identity document describing an
// instance. Error is returned if the request fails or is unable to parse
// the response.
func (c *Client) GetIAMInfo(
	ctx context.Context, params *GetIAMInfoInput, optFns ...func(*Options),
) (
	*GetIAMInfoOutput, error,
) {
	if params == nil {
		params = &GetIAMInfoInput{}
	}

	result, metadata, err := c.invokeOperation(ctx, "GetIAMInfo", params, optFns,
		addGetIAMInfoMiddleware,
	)
	if err != nil {
		return nil, err
	}

	out := result.(*GetIAMInfoOutput)
	out.ResultMetadata = metadata
	return out, nil
}

// GetIAMInfoInput provides the input parameters for GetIAMInfo operation.
type GetIAMInfoInput struct{}

// GetIAMInfoOutput provides the output parameters for GetIAMInfo operation.
type GetIAMInfoOutput struct {
	IAMInfo

	ResultMetadata middleware.Metadata
}

func addGetIAMInfoMiddleware(stack *middleware.Stack, options Options) error {
	return addAPIRequestMiddleware(stack,
		options,
		buildGetIAMInfoPath,
		buildGetIAMInfoOutput,
	)
}

func buildGetIAMInfoPath(params interface{}) (string, error) {
	return getIAMInfoPath, nil
}

func buildGetIAMInfoOutput(resp *smithyhttp.Response) (v interface{}, err error) {
	defer func() {
		closeErr := resp.Body.Close()
		if err == nil {
			err = closeErr
		} else if closeErr != nil {
			err = fmt.Errorf("response body close error: %v, original error: %w", closeErr, err)
		}
	}()

	var buff [1024]byte
	ringBuffer := smithyio.NewRingBuffer(buff[:])
	body := io.TeeReader(resp.Body, ringBuffer)

	imdsResult := &GetIAMInfoOutput{}
	if err = json.NewDecoder(body).Decode(&imdsResult.IAMInfo); err != nil {
		return nil, &smithy.DeserializationError{
			Err:      fmt.Errorf("failed to decode instance identity document, %w", err),
			Snapshot: ringBuffer.Bytes(),
		}
	}
	// Any code other success is an error
	if !strings.EqualFold(imdsResult.Code, "success") {
		return nil, fmt.Errorf("failed to get EC2 IMDS IAM info, %s",
			imdsResult.Code)
	}

	return imdsResult, nil
}

// IAMInfo provides the shape for unmarshaling an IAM info from the metadata
// API.
type IAMInfo struct {
	Code               string
	LastUpdated        time.Time
	InstanceProfileArn string
	InstanceProfileID  string
}