package stacks

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

// probeTarget holds the info needed to probe a single stack.
type probeTarget struct {
	stackName     string
	containerName string
	checks        []HealthCheckItem
}

// RunHealthProbes runs controller-side health probes for all running stacks
// that have healthcheck configuration and whose interval has elapsed.
// Called by the scheduler every minute.
func (m *Manager) RunHealthProbes() error {
	// Phase 1: collect targets (under lock)
	var noProbe []noProbeStack
	m.mu.RLock()
	var targets []probeTarget
	skippedNotDue := 0
	skippedNoContainer := 0
	for name, stack := range m.stacks {
		// StateDegraded (R-51) is probed too: its live members still answer, and the probe result
		// only ever overrides StateRunning below, so a degraded stack can never be masked as unhealthy.
		if stack.State != StateRunning && stack.State != StateUnhealthy && stack.State != StateDegraded {
			continue
		}
		hc := stack.Meta.HealthCheck
		if hc == nil || len(hc.Checks) == 0 {
			continue
		}

		// Check if interval has elapsed since last probe.
		// Fast 10s probes until healthy, then normal interval (default 5m).
		// When HealthProbe is nil (just started/restarted), probe immediately.
		interval := parseInterval(hc.Interval)
		if stack.HealthProbe != nil {
			effectiveInterval := interval
			if !stack.HealthProbe.Healthy {
				effectiveInterval = 10 * time.Second
			}
			if time.Since(stack.HealthProbe.LastCheck) < effectiveInterval {
				skippedNotDue++
				if m.isDebug() {
					sinceLastCheck := time.Since(stack.HealthProbe.LastCheck).Round(time.Second)
					m.logger.Printf("[DEBUG] [stacks] RunHealthProbes: skipping %s — last check %s ago, effective interval %s, healthy=%v",
						name, sinceLastCheck, effectiveInterval, stack.HealthProbe.Healthy)
				}
				continue
			}
		}

		// Find the main container to probe. R-630: a stack whose check resolves to no container
		// used to be skipped SILENTLY — paperless-ngx's probe had therefore never run on any box,
		// and nothing on any screen could say so. It now gets a RESULT that says why, so the app
		// page can tell "checked and healthy" from "never checked".
		containerName, candidates := findProbeContainerMeta(name, &stack.Meta, stack.Containers)
		if containerName == "" {
			skippedNoContainer++
			noProbe = append(noProbe, noProbeStack{name: name, candidates: candidates})
			continue
		}

		targets = append(targets, probeTarget{
			stackName:     name,
			containerName: containerName,
			checks:        hc.Checks,
		})
	}
	m.mu.RUnlock()

	// Record the "no probe container" stacks OUTSIDE the read lock, then write their results under
	// the write lock — the same shape the probe results themselves use.
	for _, np := range noProbe {
		m.mu.Lock()
		if s, ok := m.stacks[np.name]; ok {
			s.HealthProbe = &HealthProbeResult{
				Healthy:   true, // never RED on our own inability to look — R-630's whole point
				LastCheck: m.now(),
				Details: []HealthCheckDetail{{
					Type:       "none",
					Target:     np.name,
					Healthy:    true,
					Error:      MsgHealthNoProbeContainer,
					MessageKey: KeyHealthNoProbeContainer,
				}},
			}
		}
		m.mu.Unlock()
		if m.isDebug() {
			m.logger.Printf("[DEBUG] [stacks] RunHealthProbes: %s has a health check but no container to probe — candidates: %v", np.name, np.candidates)
		}
	}

	if m.isDebug() {
		m.logger.Printf("[DEBUG] [stacks] RunHealthProbes: collected %d targets (%d skipped not due, %d skipped no container)",
			len(targets), skippedNotDue, skippedNoContainer)
	}

	if len(targets) == 0 {
		return nil
	}

	// Phase 2: run all probes concurrently (no lock held)
	type probeResult struct {
		stackName string
		result    *HealthProbeResult
	}

	results := make([]probeResult, len(targets))
	var wg sync.WaitGroup

	for i, t := range targets {
		wg.Add(1)
		go func(idx int, t probeTarget) {
			defer wg.Done()
			result := m.runChecks(t)
			results[idx] = probeResult{stackName: t.stackName, result: result}
		}(i, t)
	}
	wg.Wait()

	// Phase 3: apply results and log (under lock)
	m.mu.Lock()
	okCount, failCount := 0, 0
	for _, pr := range results {
		stack, ok := m.stacks[pr.stackName]
		if !ok {
			continue
		}
		stack.HealthProbe = pr.result

		if pr.result.Healthy {
			okCount++
			// If Docker says running and probe is healthy, ensure state is running
			// (clears a previous unhealthy override)
			if stack.State == StateUnhealthy {
				stack.State = StateRunning
			}
		} else {
			failCount++
			if stack.State == StateRunning {
				stack.State = StateUnhealthy
			}
		}
	}
	m.mu.Unlock()

	// Summary log
	if failCount > 0 {
		m.logger.Printf("[WARN] Health probes: %d ok, %d unhealthy (of %d probed)", okCount, failCount, len(targets))
	} else {
		m.logger.Printf("[INFO] Health probes: %d ok (of %d probed)", okCount, len(targets))
	}

	return nil
}

// runChecks executes all health check items for a single stack target.
func (m *Manager) runChecks(t probeTarget) *HealthProbeResult {
	result := &HealthProbeResult{
		LastCheck: time.Now(),
		Healthy:   true,
	}

	for _, check := range t.checks {
		detail := m.runSingleCheck(t.containerName, check)
		result.Details = append(result.Details, detail)

		if detail.Healthy {
			if m.isDebug() {
				if detail.Status > 0 {
					m.logger.Printf("[DEBUG] Health probe %s: %s %s :%d%s → %d (%s)",
						t.stackName, strings.ToUpper(check.Type), methodOrEmpty(check), check.Port, check.Path, detail.Status, detail.Latency)
				} else {
					m.logger.Printf("[DEBUG] Health probe %s: TCP :%d → ok (%s)",
						t.stackName, check.Port, detail.Latency)
				}
			}
		} else {
			result.Healthy = false
			m.logger.Printf("[WARN] Health probe %s: %s %s :%d%s → %s",
				t.stackName, strings.ToUpper(check.Type), methodOrEmpty(check), check.Port, check.Path, detail.Error)
		}
	}

	return result
}

// runSingleCheck executes one health check item and returns the result.
func (m *Manager) runSingleCheck(containerName string, check HealthCheckItem) HealthCheckDetail {
	target := fmt.Sprintf(":%d%s", check.Port, check.Path)

	switch check.Type {
	case "tcp":
		return m.probeTCP(containerName, check.Port, target)
	case "http", "api":
		return m.probeHTTP(containerName, check, target)
	default:
		return HealthCheckDetail{
			Type:    check.Type,
			Target:  target,
			Healthy: false,
			Error:   fmt.Sprintf("unknown check type: %s", check.Type),
		}
	}
}

// probeTCP tests if a TCP port is reachable on the container.
func (m *Manager) probeTCP(containerName string, port int, target string) HealthCheckDetail {
	start := time.Now()
	addr := net.JoinHostPort(containerName, fmt.Sprintf("%d", port))
	conn, err := net.DialTimeout("tcp", addr, 5*time.Second)
	latency := time.Since(start)

	detail := HealthCheckDetail{
		Type:    "tcp",
		Target:  target,
		Latency: formatLatency(latency),
	}

	if err != nil {
		detail.Healthy = false
		detail.Error = err.Error()
	} else {
		conn.Close()
		detail.Healthy = true
	}
	return detail
}

// probeHTTP makes an HTTP request to the container and evaluates the result.
// For "http" type: any response = healthy. For "api" type: validates expect rules.
func (m *Manager) probeHTTP(containerName string, check HealthCheckItem, target string) HealthCheckDetail {
	url := fmt.Sprintf("http://%s:%d%s", containerName, check.Port, check.Path)
	method := check.Method
	if method == "" {
		method = "GET"
	}

	start := time.Now()

	client := &http.Client{
		Timeout: 5 * time.Second,
		CheckRedirect: func(req *http.Request, via []*http.Request) error {
			return http.ErrUseLastResponse
		},
	}

	req, err := http.NewRequest(method, url, nil)
	if err != nil {
		return HealthCheckDetail{
			Type:    check.Type,
			Target:  target,
			Healthy: false,
			Error:   fmt.Sprintf("bad request: %v", err),
			Latency: "0ms",
		}
	}

	resp, err := client.Do(req)
	latency := time.Since(start)

	detail := HealthCheckDetail{
		Type:    check.Type,
		Target:  target,
		Latency: formatLatency(latency),
	}

	if err != nil {
		detail.Healthy = false
		detail.Error = err.Error()
		return detail
	}
	defer resp.Body.Close()
	detail.Status = resp.StatusCode

	// For "http" type, any response means the service is alive
	if check.Type == "http" {
		detail.Healthy = true
		return detail
	}

	// For "api" type, validate expectations
	if check.Expect == nil {
		// No expectations = just check for a response (same as http)
		detail.Healthy = true
		return detail
	}

	// Check expected status code
	if check.Expect.Status > 0 && resp.StatusCode != check.Expect.Status {
		detail.Healthy = false
		detail.Error = fmt.Sprintf("expected status %d, got %d", check.Expect.Status, resp.StatusCode)
		return detail
	}

	// Check expected body content
	if check.Expect.BodyContains != "" {
		body, err := io.ReadAll(io.LimitReader(resp.Body, 8192)) // read up to 8KB
		if err != nil {
			detail.Healthy = false
			detail.Error = fmt.Sprintf("reading body: %v", err)
			return detail
		}
		if !strings.Contains(string(body), check.Expect.BodyContains) {
			detail.Healthy = false
			detail.Error = fmt.Sprintf("body missing expected string %q", check.Expect.BodyContains)
			return detail
		}
	}

	detail.Healthy = true
	return detail
}

// The one sentence R-630 adds. Hungarian bytes by default, the key beside it — util.MsgError's
// contract, because HealthProbe is serialised raw to the API and has no localisation seam of its own.
const (
	MsgHealthNoProbeContainer = "Nem futott egészségellenőrzés: nincs hozzá tartozó konténer."
	KeyHealthNoProbeContainer = "health.no_probe_container"
)

// noProbeStack is a stack that declares a health check which resolves to no container.
type noProbeStack struct {
	name       string
	candidates []string
}

// findProbeContainer returns the container to probe for a stack, and the candidates it rejected.
//
// Four rules, in order (R-630):
//
//  1. the container whose name EQUALS the stack name;
//  2. the container named by `healthcheck.container` in `.felhom.yml`;
//  3. a prefix match — but ONLY when exactly one running container matches. The old code took the
//     FIRST prefix match, which for `immich` (four `immich-*` containers and no exact match) meant
//     whichever the container list happened to yield, and which was seen live on `outline` probing
//     `outline-postgres:3000` during startup because the exactly-named container was not up yet;
//  4. nothing — and the CANDIDATES come back with it, because "no container" with no list is the
//     silence this whole row is about.
//
// `meta` may be nil; the caller is not required to have one.
func findProbeContainerMeta(stackName string, meta *Metadata, containers []ContainerInfo) (string, []string) {
	probeable := func(c ContainerInfo) bool {
		return c.State == StateRunning || c.State == StateUnhealthy
	}
	for _, c := range containers {
		if c.Name == stackName && probeable(c) {
			return c.Name, nil
		}
	}
	if meta != nil && meta.HealthCheck != nil && meta.HealthCheck.Container != "" {
		want := meta.HealthCheck.Container
		for _, c := range containers {
			if c.Name == want && probeable(c) {
				return c.Name, nil
			}
		}
	}
	var prefix []string
	for _, c := range containers {
		if strings.HasPrefix(c.Name, stackName) && probeable(c) {
			prefix = append(prefix, c.Name)
		}
	}
	if len(prefix) == 1 {
		return prefix[0], nil
	}
	// Ambiguous or empty: name what was seen so the log and the page can say why.
	all := make([]string, 0, len(containers))
	for _, c := range containers {
		all = append(all, c.Name+"("+string(c.State)+")")
	}
	return "", all
}

// findProbeContainer is the one-value form kept for callers that only want the name.
func findProbeContainer(stackName string, containers []ContainerInfo) string {
	n, _ := findProbeContainerMeta(stackName, nil, containers)
	return n
}

// parseInterval parses a duration string like "5m", "30s", "1h".
// Returns 5 minutes as default if parsing fails.
func parseInterval(s string) time.Duration {
	if s == "" {
		return 5 * time.Minute
	}
	d, err := time.ParseDuration(s)
	if err != nil {
		return 5 * time.Minute
	}
	return d
}

// formatLatency formats a duration as a human-readable latency string.
func formatLatency(d time.Duration) string {
	if d < time.Millisecond {
		return fmt.Sprintf("%dµs", d.Microseconds())
	}
	if d < time.Second {
		return fmt.Sprintf("%dms", d.Milliseconds())
	}
	return fmt.Sprintf("%.1fs", d.Seconds())
}

// methodOrEmpty returns the method string for logging, or empty for non-api checks.
func methodOrEmpty(check HealthCheckItem) string {
	if check.Type == "api" && check.Method != "" {
		return check.Method
	}
	if check.Type == "api" {
		return "GET"
	}
	return "GET"
}