package deploy

import (
	"context"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"
)

const ec2IMDSBase = "http://169.254.169.254/latest"

type CloudInstanceMeta struct {
	VpcID    string `json:"vpc_id,omitempty"`
	SubnetID string `json:"subnet_id,omitempty"`
	Region   string `json:"region,omitempty"`
}

func (m CloudInstanceMeta) Present() bool {
	return strings.TrimSpace(m.VpcID) != "" || strings.TrimSpace(m.SubnetID) != "" || strings.TrimSpace(m.Region) != ""
}

var ec2IMDSReadMeta = readEC2InstanceMetaImpl

func ReadEC2InstanceMeta() CloudInstanceMeta {
	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
	defer cancel()
	meta, _ := ec2IMDSReadMeta(ctx)
	return meta
}

func readEC2InstanceMetaImpl(ctx context.Context) (CloudInstanceMeta, error) {
	token, err := fetchEC2IMDSToken(ctx)
	if err != nil {
		return CloudInstanceMeta{}, err
	}
	region, _ := fetchEC2IMDSPath(ctx, token, "meta-data/placement/region")
	if strings.TrimSpace(region) == "" {
		az, _ := fetchEC2IMDSPath(ctx, token, "meta-data/placement/availability-zone")
		az = strings.TrimSpace(az)
		if len(az) > 1 {
			region = az[:len(az)-1]
		}
	}
	macs, err := fetchEC2IMDSPath(ctx, token, "meta-data/network/interfaces/macs/")
	if err != nil || strings.TrimSpace(macs) == "" {
		return CloudInstanceMeta{Region: strings.TrimSpace(region)}, nil
	}
	mac := strings.TrimSpace(strings.Split(macs, "\n")[0])
	if mac == "" {
		return CloudInstanceMeta{Region: strings.TrimSpace(region)}, nil
	}
	if !strings.HasSuffix(mac, "/") {
		mac += "/"
	}
	base := "meta-data/network/interfaces/macs/" + mac
	vpcID, _ := fetchEC2IMDSPath(ctx, token, base+"vpc-id")
	subnetID, _ := fetchEC2IMDSPath(ctx, token, base+"subnet-id")
	return CloudInstanceMeta{VpcID: strings.TrimSpace(vpcID), SubnetID: strings.TrimSpace(subnetID), Region: strings.TrimSpace(region)}, nil
}

func fetchEC2IMDSToken(ctx context.Context) (string, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodPut, ec2IMDSBase+"/api/token", nil)
	if err != nil {
		return "", err
	}
	req.Header.Set("X-aws-ec2-metadata-token-ttl-seconds", "60")
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("imds token HTTP %d", resp.StatusCode)
	}
	body, err := io.ReadAll(io.LimitReader(resp.Body, 128))
	return strings.TrimSpace(string(body)), err
}

func fetchEC2IMDSPath(ctx context.Context, token, path string) (string, error) {
	path = strings.TrimPrefix(path, "/")
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, ec2IMDSBase+"/"+path, nil)
	if err != nil {
		return "", err
	}
	if token != "" {
		req.Header.Set("X-aws-ec2-metadata-token", token)
	}
	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("imds HTTP %d", resp.StatusCode)
	}
	body, err := io.ReadAll(io.LimitReader(resp.Body, 64<<10))
	return strings.TrimSpace(string(body)), err
}

// ec2IMDSToken and ec2IMDSFetch are shared helpers for cloud venue probing.
func ec2IMDSToken(ctx context.Context) (string, error) { return fetchEC2IMDSToken(ctx) }
func ec2IMDSFetch(ctx context.Context, token, path string) (string, error) {
	return fetchEC2IMDSPath(ctx, token, path)
}