package worker

import (
	"context"
	"sync"
	"time"

	"github.com/orchard9/rdev/internal/domain"
	"github.com/orchard9/rdev/internal/logging"
	"github.com/orchard9/rdev/internal/metrics"
	"github.com/orchard9/rdev/internal/port"
)

// ExternalHealthChecker runs periodic health checks on external systems
// (registry, CI, git) and caches the results for the /ready endpoint.
type ExternalHealthChecker struct {
	registry port.RegistryChecker       // zot
	ci       port.ExternalHealthChecker // woodpecker
	git      port.ExternalHealthChecker // gitea

	interval time.Duration

	// Internal state (thread-safe)
	mu       sync.RWMutex
	statuses map[domain.ExternalSystem]domain.ExternalSystemStatus

	// Lifecycle
	ctx    context.Context
	cancel context.CancelFunc
	wg     sync.WaitGroup
}

// ExternalHealthConfig configures the health checker.
type ExternalHealthConfig struct {
	// CheckInterval is how often to check external systems. Default: 30s.
	CheckInterval time.Duration
}

// DefaultExternalHealthConfig returns sensible defaults.
func DefaultExternalHealthConfig() ExternalHealthConfig {
	return ExternalHealthConfig{
		CheckInterval: 30 * time.Second,
	}
}

// NewExternalHealthChecker creates a new external health checker.
// All checker parameters are optional (nil means skip that system).
func NewExternalHealthChecker(
	registry port.RegistryChecker,
	ci port.ExternalHealthChecker,
	git port.ExternalHealthChecker,
	cfg ExternalHealthConfig,
) *ExternalHealthChecker {
	if cfg.CheckInterval == 0 {
		cfg.CheckInterval = 30 * time.Second
	}

	ctx, cancel := context.WithCancel(context.Background())

	return &ExternalHealthChecker{
		registry: registry,
		ci:       ci,
		git:      git,
		interval: cfg.CheckInterval,
		statuses: make(map[domain.ExternalSystem]domain.ExternalSystemStatus),
		ctx:      ctx,
		cancel:   cancel,
	}
}

// Start begins the background check loop.
func (c *ExternalHealthChecker) Start() {
	log := logging.FromContext(c.ctx).WithWorker("external-health")
	log.Info("external health checker started", "interval", c.interval)

	c.wg.Add(1)
	go c.checkLoop()
}

// Stop gracefully shuts down the checker.
func (c *ExternalHealthChecker) Stop() {
	log := logging.FromContext(c.ctx).WithWorker("external-health")
	log.Info("external health checker stopping")
	c.cancel()
	c.wg.Wait()
	log.Info("external health checker stopped")
}

// GetStatus returns the cached status for a specific system.
func (c *ExternalHealthChecker) GetStatus(system domain.ExternalSystem) (domain.ExternalSystemStatus, bool) {
	c.mu.RLock()
	defer c.mu.RUnlock()
	status, ok := c.statuses[system]
	return status, ok
}

// GetAllStatuses returns a copy of all cached statuses.
func (c *ExternalHealthChecker) GetAllStatuses() map[domain.ExternalSystem]domain.ExternalSystemStatus {
	c.mu.RLock()
	defer c.mu.RUnlock()

	result := make(map[domain.ExternalSystem]domain.ExternalSystemStatus, len(c.statuses))
	for k, v := range c.statuses {
		result[k] = v
	}
	return result
}

// checkLoop runs periodic health checks.
func (c *ExternalHealthChecker) checkLoop() {
	defer c.wg.Done()

	// Run immediately on start
	c.runChecks()

	ticker := time.NewTicker(c.interval)
	defer ticker.Stop()

	for {
		select {
		case <-c.ctx.Done():
			return
		case <-ticker.C:
			c.runChecks()
		}
	}
}

// runChecks performs health checks on all configured systems in parallel.
func (c *ExternalHealthChecker) runChecks() {
	ctx, cancel := context.WithTimeout(c.ctx, TimeoutHealthCheck)
	defer cancel()

	var wg sync.WaitGroup
	results := make(chan domain.ExternalSystemStatus, 3)

	// Check registry (zot)
	if c.registry != nil {
		wg.Add(1)
		go func() {
			defer wg.Done()
			regStatus := c.registry.Check(ctx)
			// Convert domain.RegistryStatus to domain.ExternalSystemStatus
			status := domain.ExternalSystemStatus{
				System:      domain.ExternalSystemRegistry,
				Healthy:     regStatus.Healthy,
				URL:         regStatus.URL,
				Error:       regStatus.Error,
				LastChecked: regStatus.LastChecked,
			}
			// Parse latency string (e.g., "45ms") to duration
			if regStatus.Latency != "" {
				if d, err := time.ParseDuration(regStatus.Latency); err == nil {
					status.Latency = d
				}
			}
			if status.Healthy {
				status.LastHealthy = status.LastChecked
			}
			results <- status
		}()
	}

	// Check CI (woodpecker)
	if c.ci != nil {
		wg.Add(1)
		go func() {
			defer wg.Done()
			results <- c.ci.Check(ctx)
		}()
	}

	// Check git (gitea)
	if c.git != nil {
		wg.Add(1)
		go func() {
			defer wg.Done()
			results <- c.git.Check(ctx)
		}()
	}

	// Wait for all checks to complete, then close results channel
	go func() {
		wg.Wait()
		close(results)
	}()

	// Collect results and update state
	for status := range results {
		c.updateStatus(status)
	}
}

// updateStatus updates cached status and logs/metrics on state changes.
func (c *ExternalHealthChecker) updateStatus(status domain.ExternalSystemStatus) {
	log := logging.FromContext(c.ctx).WithWorker("external-health")

	c.mu.Lock()
	defer c.mu.Unlock()

	prev, existed := c.statuses[status.System]

	// Preserve LastHealthy from previous status if current is unhealthy
	if !status.Healthy && existed && !prev.LastHealthy.IsZero() {
		status.LastHealthy = prev.LastHealthy
	}

	c.statuses[status.System] = status

	// Log state transitions
	if !existed {
		// First check
		if status.Healthy {
			log.Info("external system healthy",
				"system", status.System,
				"url", status.URL,
				"latency", status.Latency,
			)
		} else {
			log.Warn("external system unhealthy",
				"system", status.System,
				"url", status.URL,
				logging.FieldError, status.Error,
			)
		}
	} else if prev.Healthy != status.Healthy {
		// State changed
		if status.Healthy {
			log.Info("external system recovered",
				"system", status.System,
				"url", status.URL,
				"latency", status.Latency,
			)
		} else {
			log.Warn("external system became unhealthy",
				"system", status.System,
				"url", status.URL,
				logging.FieldError, status.Error,
			)
		}
	}

	// Update Prometheus metrics
	metrics.SetExternalSystemHealth(string(status.System), status.Healthy, status.Latency.Seconds())
}