package swarm

import (
	"bytes"
	"fmt"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"strconv"
	"strings"
	"text/template"

	"git.nixc.us/a250/ss-atlas/internal/config"
)

type Client struct {
	cfg *config.Config
}

func New(cfg *config.Config) *Client {
	return &Client{cfg: cfg}
}

func (c *Client) DeployStack(stackName, username, domain string) error {
	tmplPath := filepath.Join(c.cfg.TemplatePath, "stack-template.yml")
	tmplBytes, err := os.ReadFile(tmplPath)
	if err != nil {
		return fmt.Errorf("read stack template: %w", err)
	}

	t, err := template.New("stack").Parse(string(tmplBytes))
	if err != nil {
		return fmt.Errorf("parse stack template: %w", err)
	}

	data := map[string]any{
		"ID":             username,
		"Subdomain":      username,
		"Domain":         domain,
		"TraefikNetwork": c.cfg.TraefikNetwork,
	}

	var rendered bytes.Buffer
	if err := t.Execute(&rendered, data); err != nil {
		return fmt.Errorf("render stack template: %w", err)
	}

	tmpFile := filepath.Join(os.TempDir(), stackName+".yml")
	if err := os.WriteFile(tmpFile, rendered.Bytes(), 0600); err != nil {
		return fmt.Errorf("write temp stack file: %w", err)
	}
	defer os.Remove(tmpFile)

	cmd := exec.Command("docker", "stack", "deploy",
		"-c", tmpFile,
		stackName,
	)
	cmd.Env = append(os.Environ(), "DOCKER_HOST="+c.cfg.DockerHost)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("docker stack deploy: %s: %w", strings.TrimSpace(string(output)), err)
	}

	log.Printf("deployed stack %s: %s", stackName, strings.TrimSpace(string(output)))

	// Force-restart the web service so Traefik picks up label changes immediately.
	// Traefik reads labels from running task containers, not service specs, so a
	// task restart is required for routing changes to take effect.
	forceCmd := exec.Command("docker", "service", "update", "--force", stackName+"_web")
	forceCmd.Env = append(os.Environ(), "DOCKER_HOST="+c.cfg.DockerHost)
	if forceOut, forceErr := forceCmd.CombinedOutput(); forceErr != nil {
		log.Printf("warn: force-update %s_web: %s", stackName, strings.TrimSpace(string(forceOut)))
	}

	return nil
}

func (c *Client) RemoveStack(stackName string) error {
	cmd := exec.Command("docker", "stack", "rm", stackName)
	cmd.Env = append(os.Environ(), "DOCKER_HOST="+c.cfg.DockerHost)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("docker stack rm: %s: %w", strings.TrimSpace(string(output)), err)
	}

	log.Printf("removed stack %s: %s", stackName, strings.TrimSpace(string(output)))
	return nil
}

func (c *Client) StackExists(stackName string) (bool, error) {
	cmd := exec.Command("docker", "stack", "ls", "--format", "{{.Name}}")
	cmd.Env = append(os.Environ(), "DOCKER_HOST="+c.cfg.DockerHost)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return false, fmt.Errorf("docker stack ls: %w", err)
	}

	for _, line := range strings.Split(string(output), "\n") {
		if strings.TrimSpace(line) == stackName {
			return true, nil
		}
	}
	return false, nil
}

// GetWebReplicas returns the desired replica count for <stackName>_web.
// Returns 0 if the service does not exist.
func (c *Client) GetWebReplicas(stackName string) (int, error) {
	cmd := exec.Command("docker", "service", "inspect",
		"--format", "{{.Spec.Mode.Replicated.Replicas}}",
		stackName+"_web",
	)
	cmd.Env = append(os.Environ(), "DOCKER_HOST="+c.cfg.DockerHost)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return 0, nil
	}

	n, err := strconv.Atoi(strings.TrimSpace(string(output)))
	if err != nil {
		return 0, nil
	}
	return n, nil
}

// ScaleStack sets the desired replica count for <stackName>_web.
func (c *Client) ScaleStack(stackName string, replicas int) error {
	svc := fmt.Sprintf("%s_web=%d", stackName, replicas)
	cmd := exec.Command("docker", "service", "scale", svc)
	cmd.Env = append(os.Environ(), "DOCKER_HOST="+c.cfg.DockerHost)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("scale stack %s: %s: %w", stackName, strings.TrimSpace(string(output)), err)
	}

	log.Printf("scaled %s_web to %d: %s", stackName, replicas, strings.TrimSpace(string(output)))
	return nil
}

// RestartStack force-restarts the web service, triggering a fresh container.
func (c *Client) RestartStack(stackName string) error {
	cmd := exec.Command("docker", "service", "update", "--force", stackName+"_web")
	cmd.Env = append(os.Environ(), "DOCKER_HOST="+c.cfg.DockerHost)

	output, err := cmd.CombinedOutput()
	if err != nil {
		return fmt.Errorf("restart stack %s: %s: %w", stackName, strings.TrimSpace(string(output)), err)
	}

	log.Printf("restarted %s_web: %s", stackName, strings.TrimSpace(string(output)))
	return nil
}