package swarm

import (
	"context"
	"encoding/json"
	"fmt"
	"net"
	"net/http"
	"net/url"
	"strings"
	"time"
)

// Config holds collector configuration.
type Config struct {
	LiteLLMBaseURL string
	LiteLLMAPIKey  string
	HTTPTimeout    time.Duration
	DockerSocket   string // defaults to /var/run/docker.sock
}

// dockerContainer is the shape returned by GET /containers/json.
type dockerContainer struct {
	ID     string            `json:"Id"`
	Names  []string          `json:"Names"`
	State  string            `json:"State"`
	Labels map[string]string `json:"Labels"`
}

// dockerContainerDetail is the shape returned by GET /containers/{id}/json.
type dockerContainerDetail struct {
	State struct {
		Status    string `json:"Status"`
		Running   bool   `json:"Running"`
		StartedAt string `json:"StartedAt"`
		Health    *struct {
			Status string `json:"Status"`
		} `json:"Health"`
	} `json:"State"`
}

func newDockerClient(socketPath string) *http.Client {
	if socketPath == "" {
		socketPath = "/var/run/docker.sock"
	}
	return &http.Client{
		Transport: &http.Transport{
			DialContext: func(ctx context.Context, _, _ string) (net.Conn, error) {
				return (&net.Dialer{}).DialContext(ctx, "unix", socketPath)
			},
		},
	}
}

// CollectAll lists all containers labeled agentmon.monitor=true and collects
// a ServiceSnapshot for each.
func CollectAll(ctx context.Context, cfg Config) ([]ServiceSnapshot, error) {
	dockerClient := newDockerClient(cfg.DockerSocket)
	httpClient := &http.Client{Timeout: cfg.HTTPTimeout}

	filters := url.QueryEscape(`{"label":["agentmon.monitor=true"]}`)
	req, err := http.NewRequestWithContext(ctx, http.MethodGet,
		"http://localhost/v1.41/containers/json?all=1&filters="+filters, nil)
	if err != nil {
		return nil, err
	}

	resp, err := dockerClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("docker API unavailable: %w", err)
	}
	defer resp.Body.Close()

	var containers []dockerContainer
	if err := json.NewDecoder(resp.Body).Decode(&containers); err != nil {
		return nil, fmt.Errorf("docker API parse error: %w", err)
	}

	var snapshots []ServiceSnapshot
	for _, c := range containers {
		snapshots = append(snapshots, collectOne(ctx, c, dockerClient, httpClient, cfg))
	}
	return snapshots, nil
}

func collectOne(ctx context.Context, c dockerContainer, dockerClient, httpClient *http.Client, cfg Config) ServiceSnapshot {
	name := containerName(c)
	snap := ServiceSnapshot{
		Name:           name,
		Role:           c.Labels["agentmon.role"],
		ContainerState: c.State,
		HealthState:    "none",
		Status:         "down",
	}

	// Inspect for health state and uptime (not in list response).
	req, err := http.NewRequestWithContext(ctx, http.MethodGet,
		"http://localhost/v1.41/containers/"+c.ID+"/json", nil)
	if err == nil {
		if resp, err := dockerClient.Do(req); err == nil {
			var detail dockerContainerDetail
			if json.NewDecoder(resp.Body).Decode(&detail) == nil {
				if detail.State.Health != nil {
					snap.HealthState = detail.State.Health.Status
				}
				if detail.State.Running && detail.State.StartedAt != "" {
					if t, err := time.Parse(time.RFC3339Nano, detail.State.StartedAt); err == nil {
						snap.UptimeSec = int64(time.Since(t).Seconds())
					}
				}
			}
			resp.Body.Close()
		}
	}

	port := c.Labels["agentmon.port"]
	switch snap.Role {
	case "llm-proxy":
		collectLLMProxy(ctx, &snap, httpClient, cfg)
	case "search":
		collectHTTPProbe(ctx, &snap, httpClient, "http://localhost:"+port+"/")
	case "mcp":
		collectPortProbe(&snap, port)
	}

	snap.Status = deriveStatus(snap)
	return snap
}

func containerName(c dockerContainer) string {
	if len(c.Names) > 0 {
		return strings.TrimPrefix(c.Names[0], "/")
	}
	return c.ID[:12]
}

func collectLLMProxy(ctx context.Context, snap *ServiceSnapshot, client *http.Client, cfg Config) {
	if snap.Extra == nil {
		snap.Extra = make(map[string]any)
	}

	req, _ := http.NewRequestWithContext(ctx, http.MethodGet, cfg.LiteLLMBaseURL+"/health/liveliness", nil)
	if resp, err := client.Do(req); err == nil {
		code := resp.StatusCode
		snap.HTTPStatus = &code
		resp.Body.Close()
	}

	if cfg.LiteLLMAPIKey != "" {
		req, _ := http.NewRequestWithContext(ctx, http.MethodGet, cfg.LiteLLMBaseURL+"/v2/model/info", nil)
		req.Header.Set("Authorization", "Bearer "+cfg.LiteLLMAPIKey)
		if resp, err := client.Do(req); err == nil {
			defer resp.Body.Close()
			var result struct {
				Data []struct{} `json:"data"`
			}
			if json.NewDecoder(resp.Body).Decode(&result) == nil {
				snap.Extra["model_count"] = len(result.Data)
			}
		}
	}
}

func collectHTTPProbe(ctx context.Context, snap *ServiceSnapshot, client *http.Client, target string) {
	start := time.Now()
	req, _ := http.NewRequestWithContext(ctx, http.MethodGet, target, nil)
	if resp, err := client.Do(req); err == nil {
		code := resp.StatusCode
		snap.HTTPStatus = &code
		resp.Body.Close()
		if snap.Extra == nil {
			snap.Extra = make(map[string]any)
		}
		snap.Extra["response_ms"] = time.Since(start).Milliseconds()
	}
}

func collectPortProbe(snap *ServiceSnapshot, port string) {
	if port == "" {
		return
	}
	conn, err := net.DialTimeout("tcp", "localhost:"+port, 2*time.Second)
	reachable := err == nil
	if conn != nil {
		conn.Close()
	}
	if snap.Extra == nil {
		snap.Extra = make(map[string]any)
	}
	snap.Extra["port_reachable"] = reachable
}

// deriveStatus computes the overall status from container state + health + probes.
func deriveStatus(snap ServiceSnapshot) string {
	if snap.ContainerState != "running" {
		return "down"
	}
	if snap.HealthState == "unhealthy" {
		return "degraded"
	}
	if snap.HTTPStatus != nil && (*snap.HTTPStatus < 200 || *snap.HTTPStatus >= 400) {
		return "degraded"
	}
	if reachable, ok := snap.Extra["port_reachable"].(bool); ok && !reachable {
		return "degraded"
	}
	return "healthy"
}

// DetectIssues scans a set of snapshots for notable problems.
func DetectIssues(services []ServiceSnapshot) Issues {
	issues := Issues{}
	for _, s := range services {
		switch s.Status {
		case "down":
			issues.ServiceDown = append(issues.ServiceDown, s.Name)
		case "degraded":
			issues.ServiceDegraded = append(issues.ServiceDegraded, s.Name)
		}
		if s.Role == "llm-proxy" {
			if extra := s.Extra; extra != nil {
				if count, ok := extra["cooldown_count"].(int); ok && count > 0 {
					issues.LLMCooldowns = true
				}
			}
		}
	}
	return issues
}