package docker

import (
	"context"
	"fmt"
	"regexp"
	"strconv"
	"strings"

	"github.com/docker/docker/api/types/container"
	"github.com/docker/docker/api/types/filters"
	"github.com/docker/docker/api/types/network"
	"github.com/docker/go-connections/nat"
)

// ContainerConfig holds all parameters needed to create a managed container.
type ContainerConfig struct {
	// Name is the container name (deterministic: dw-{project}-{stage}-{tag}).
	Name string

	// Image is the full image reference including tag (e.g. "myapp:v1.2.3").
	Image string

	// Env is a list of environment variables in "KEY=VALUE" format.
	Env []string

	// ExposedPorts lists the container ports to publish (e.g. ["8080/tcp"]).
	// Each port is mapped to a random host port via Docker auto-assignment.
	ExposedPorts []string

	// NetworkName is the Docker network to attach the container to at creation.
	NetworkName string

	// NetworkID is the ID of the Docker network (used for endpoint config).
	NetworkID string

	// Labels are additional labels to apply to the container.
	// docker-watcher management labels are added automatically via Project, Stage, and InstanceID.
	Labels map[string]string

	// Project is the docker-watcher project name (used for labelling).
	Project string

	// Stage is the docker-watcher stage name (used for labelling).
	Stage string

	// InstanceID is the docker-watcher instance ID (used for labelling).
	InstanceID string
}

// sanitizeTag replaces characters that are invalid in Docker container names
// with hyphens and lowercases the result.
var invalidNameChars = regexp.MustCompile(`[^a-zA-Z0-9_.-]`)

// ContainerName builds a deterministic container name from project, stage, and tag.
func ContainerName(project, stage, tag string) string {
	sanitizeComponent := func(s string) string {
		s = invalidNameChars.ReplaceAllString(s, "-")
		return strings.Trim(s, "-")
	}
	return fmt.Sprintf("dw-%s-%s-%s", sanitizeComponent(project), sanitizeComponent(stage), sanitizeComponent(tag))
}

// CreateContainer creates a new container with the given configuration.
// It returns the container ID on success.
func (c *Client) CreateContainer(ctx context.Context, cfg ContainerConfig) (string, error) {
	// Build port bindings: each exposed port maps to a random host port.
	exposedPorts := nat.PortSet{}
	portBindings := nat.PortMap{}
	for _, p := range cfg.ExposedPorts {
		port := nat.Port(p)
		exposedPorts[port] = struct{}{}
		portBindings[port] = []nat.PortBinding{
			{HostIP: "0.0.0.0", HostPort: ""}, // empty HostPort = auto-assign
		}
	}

	// Merge docker-watcher labels with any additional labels.
	labels := make(map[string]string)
	for k, v := range cfg.Labels {
		labels[k] = v
	}
	labels[LabelProject] = cfg.Project
	labels[LabelStage] = cfg.Stage
	labels[LabelInstanceID] = cfg.InstanceID

	containerCfg := &container.Config{
		Image:        cfg.Image,
		Env:          cfg.Env,
		ExposedPorts: exposedPorts,
		Labels:       labels,
	}

	hostCfg := &container.HostConfig{
		PortBindings:  portBindings,
		RestartPolicy: container.RestartPolicy{Name: container.RestartPolicyDisabled},
	}

	// Attach to network at creation time if specified.
	var networkCfg *network.NetworkingConfig
	if cfg.NetworkName != "" {
		networkCfg = &network.NetworkingConfig{
			EndpointsConfig: map[string]*network.EndpointSettings{
				cfg.NetworkName: {
					NetworkID: cfg.NetworkID,
				},
			},
		}
	}

	resp, err := c.api.ContainerCreate(ctx, containerCfg, hostCfg, networkCfg, nil, cfg.Name)
	if err != nil {
		return "", fmt.Errorf("create container %s: %w", cfg.Name, err)
	}

	return resp.ID, nil
}

// StartContainer starts a stopped container.
func (c *Client) StartContainer(ctx context.Context, containerID string) error {
	if err := c.api.ContainerStart(ctx, containerID, container.StartOptions{}); err != nil {
		return fmt.Errorf("start container %s: %w", containerID, err)
	}
	return nil
}

// StopContainer gracefully stops a running container with the given timeout in seconds.
// A nil timeout uses the Docker default (10 seconds).
func (c *Client) StopContainer(ctx context.Context, containerID string, timeoutSeconds int) error {
	opts := container.StopOptions{}
	if timeoutSeconds > 0 {
		opts.Timeout = &timeoutSeconds
	}

	if err := c.api.ContainerStop(ctx, containerID, opts); err != nil {
		return fmt.Errorf("stop container %s: %w", containerID, err)
	}
	return nil
}

// RemoveContainer removes a container. If force is true, a running container
// will be killed before removal.
func (c *Client) RemoveContainer(ctx context.Context, containerID string, force bool) error {
	opts := container.RemoveOptions{
		Force:         force,
		RemoveVolumes: true,
	}

	if err := c.api.ContainerRemove(ctx, containerID, opts); err != nil {
		return fmt.Errorf("remove container %s: %w", containerID, err)
	}
	return nil
}

// RestartContainer restarts a container with the given timeout in seconds.
func (c *Client) RestartContainer(ctx context.Context, containerID string, timeoutSeconds int) error {
	opts := container.StopOptions{}
	if timeoutSeconds > 0 {
		opts.Timeout = &timeoutSeconds
	}

	if err := c.api.ContainerRestart(ctx, containerID, opts); err != nil {
		return fmt.Errorf("restart container %s: %w", containerID, err)
	}
	return nil
}

// ManagedContainer holds summary information about a container managed by docker-watcher.
type ManagedContainer struct {
	ID         string
	Name       string
	Image      string
	Status     string
	State      string
	Project    string
	Stage      string
	InstanceID string
	Ports      []uint16
}

// ListContainers returns all containers matching the given label filters.
// Pass nil or an empty map to list all docker-watcher managed containers.
// Label filters are key=value pairs applied as Docker label filters.
func (c *Client) ListContainers(ctx context.Context, labelFilters map[string]string) ([]ManagedContainer, error) {
	filterArgs := filters.NewArgs()

	// Always filter by the docker-watcher project label to only return managed containers.
	filterArgs.Add("label", LabelProject)

	for k, v := range labelFilters {
		if v != "" {
			filterArgs.Add("label", k+"="+v)
		} else {
			filterArgs.Add("label", k)
		}
	}

	containers, err := c.api.ContainerList(ctx, container.ListOptions{
		All:     true,
		Filters: filterArgs,
	})
	if err != nil {
		return nil, fmt.Errorf("list containers: %w", err)
	}

	result := make([]ManagedContainer, 0, len(containers))
	for _, ctr := range containers {
		name := ""
		if len(ctr.Names) > 0 {
			// Docker prefixes names with "/".
			name = strings.TrimPrefix(ctr.Names[0], "/")
		}

		var ports []uint16
		for _, p := range ctr.Ports {
			if p.PublicPort > 0 {
				ports = append(ports, p.PublicPort)
			}
		}

		result = append(result, ManagedContainer{
			ID:         ctr.ID,
			Name:       name,
			Image:      ctr.Image,
			Status:     ctr.Status,
			State:      ctr.State,
			Project:    ctr.Labels[LabelProject],
			Stage:      ctr.Labels[LabelStage],
			InstanceID: ctr.Labels[LabelInstanceID],
			Ports:      ports,
		})
	}

	return result, nil
}

// InspectContainerPort returns the host port mapped to a given container port.
// This is useful after starting a container with auto-assigned ports.
func (c *Client) InspectContainerPort(ctx context.Context, containerID string, containerPort string) (uint16, error) {
	inspect, err := c.api.ContainerInspect(ctx, containerID)
	if err != nil {
		return 0, fmt.Errorf("inspect container %s: %w", containerID, err)
	}

	port := nat.Port(containerPort)
	bindings, ok := inspect.NetworkSettings.Ports[port]
	if !ok || len(bindings) == 0 {
		return 0, fmt.Errorf("container %s: no binding for port %s", containerID, containerPort)
	}

	var hostPort uint16
	for _, b := range bindings {
		if b.HostPort != "" {
			parsed := parsePort(b.HostPort)
			if parsed > 0 {
				hostPort = parsed
				break
			}
		}
	}

	if hostPort == 0 {
		return 0, fmt.Errorf("container %s: no host port for %s", containerID, containerPort)
	}

	return hostPort, nil
}

// parsePort converts a port string to uint16. Returns 0 on failure.
func parsePort(s string) uint16 {
	n, err := strconv.ParseUint(s, 10, 16)
	if err != nil {
		return 0
	}
	return uint16(n)
}