// Package handlers provides HTTP handlers for the rdev API.
package handlers

import (
	"context"
	"fmt"
	"net/http"
	"strings"
	"time"

	"github.com/orchard9/rdev/internal/circuitbreaker"
	"github.com/orchard9/rdev/internal/domain"
	"github.com/orchard9/rdev/internal/metrics"
	"github.com/orchard9/rdev/internal/port"
	"github.com/orchard9/rdev/pkg/api"
)

// ExecutorHealthChecker reports whether a background executor is running.
type ExecutorHealthChecker interface {
	Running() bool
	WorkerID() string
}

// ExternalHealthStatusProvider provides cached external system health statuses.
type ExternalHealthStatusProvider interface {
	GetAllStatuses() map[domain.ExternalSystem]domain.ExternalSystemStatus
}

// HealthHandler handles health and readiness checks.
type HealthHandler struct {
	serviceName     string
	db              port.DatabasePinger
	k8sChecker      port.KubernetesChecker
	agentRegistry   port.CodeAgentRegistry
	workExecutor    ExecutorHealthChecker
	registryChecker port.RegistryChecker
	externalChecker ExternalHealthStatusProvider
}

// NewHealthHandler creates a new health handler with dependencies.
func NewHealthHandler(serviceName string, db port.DatabasePinger, k8sChecker port.KubernetesChecker) *HealthHandler {
	return &HealthHandler{
		serviceName: serviceName,
		db:          db,
		k8sChecker:  k8sChecker,
	}
}

// WithAgentRegistry adds a code agent registry for health monitoring.
func (h *HealthHandler) WithAgentRegistry(registry port.CodeAgentRegistry) *HealthHandler {
	h.agentRegistry = registry
	return h
}

// WithWorkExecutor adds a work executor for health monitoring.
func (h *HealthHandler) WithWorkExecutor(executor ExecutorHealthChecker) *HealthHandler {
	h.workExecutor = executor
	return h
}

// WithRegistryChecker adds a registry checker for health monitoring.
func (h *HealthHandler) WithRegistryChecker(checker port.RegistryChecker) *HealthHandler {
	h.registryChecker = checker
	return h
}

// WithExternalHealthChecker adds a cached external health checker for monitoring.
func (h *HealthHandler) WithExternalHealthChecker(checker ExternalHealthStatusProvider) *HealthHandler {
	h.externalChecker = checker
	return h
}

// Health returns a simple liveness check.
// This should be lightweight and only fail if the process is unhealthy.
// GET /health
func (h *HealthHandler) Health(w http.ResponseWriter, r *http.Request) {
	api.WriteSuccess(w, r, map[string]string{
		"status":  "ok",
		"service": h.serviceName,
	})
}

// Ready returns a readiness check with dependency health.
// This checks all required dependencies (database, k8s) and returns
// 503 if any are unhealthy.
// GET /ready
func (h *HealthHandler) Ready(w http.ResponseWriter, r *http.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), TimeoutFastLookup)
	defer cancel()

	checks := make(map[string]CheckResult)
	allHealthy := true

	// Database check
	if h.db != nil {
		dbCheck := h.checkDatabase(ctx)
		checks["database"] = dbCheck
		if !dbCheck.Healthy {
			allHealthy = false
		}
	}

	// Kubernetes check
	if h.k8sChecker != nil {
		k8sCheck := h.checkKubernetes(ctx)
		checks["kubernetes"] = k8sCheck
		if !k8sCheck.Healthy {
			allHealthy = false
		}
	}

	// Code agent checks (informational - don't affect overall readiness)
	if h.agentRegistry != nil {
		agentChecks := h.checkCodeAgents(ctx)
		for name, check := range agentChecks {
			checks["agent:"+name] = check
		}
	}

	// Work executor check (informational)
	if h.workExecutor != nil {
		checks["work_executor"] = h.checkWorkExecutor()
	}

	// Registry check (informational - doesn't affect overall readiness)
	if h.registryChecker != nil {
		checks["registry"] = h.checkRegistry(ctx)
	}

	// External system checks (cached, from background worker)
	if h.externalChecker != nil {
		for system, status := range h.externalChecker.GetAllStatuses() {
			checks["external:"+string(system)] = CheckResult{
				Healthy:   status.Healthy,
				Message:   status.Error,
				Latency:   status.Latency.String(),
				LastCheck: status.LastChecked,
			}
			if status.Healthy {
				checks["external:"+string(system)] = CheckResult{
					Healthy:   true,
					Message:   "connected",
					Latency:   status.Latency.String(),
					LastCheck: status.LastChecked,
				}
			}
		}
	}

	response := ReadinessResponse{
		Status:  "ready",
		Service: h.serviceName,
		Checks:  checks,
	}

	if !allHealthy {
		response.Status = "not_ready"
		api.WriteError(w, r, http.StatusServiceUnavailable, "NOT_READY",
			"Service not ready - one or more checks failed")
		return
	}

	api.WriteSuccess(w, r, response)
}

// checkDatabase performs a database health check.
func (h *HealthHandler) checkDatabase(ctx context.Context) CheckResult {
	start := time.Now()
	err := h.db.PingContext(ctx)
	latency := time.Since(start)

	if err != nil {
		return CheckResult{
			Healthy:   false,
			Message:   "connection failed: " + err.Error(),
			Latency:   latency.String(),
			LastCheck: time.Now().UTC(),
		}
	}

	return CheckResult{
		Healthy:   true,
		Message:   "connected",
		Latency:   latency.String(),
		LastCheck: time.Now().UTC(),
	}
}

// checkKubernetes performs a Kubernetes API health check.
func (h *HealthHandler) checkKubernetes(_ context.Context) CheckResult {
	start := time.Now()

	// Try to get server version - lightweight API call
	_, err := h.k8sChecker.ServerVersion()
	latency := time.Since(start)

	if err != nil {
		// Check if it's a timeout or connection error
		msg := err.Error()
		if strings.Contains(msg, "timeout") || strings.Contains(msg, "deadline") {
			msg = "connection timeout"
		} else if strings.Contains(msg, "refused") {
			msg = "connection refused"
		}

		return CheckResult{
			Healthy:   false,
			Message:   msg,
			Latency:   latency.String(),
			LastCheck: time.Now().UTC(),
		}
	}

	return CheckResult{
		Healthy:   true,
		Message:   "connected",
		Latency:   latency.String(),
		LastCheck: time.Now().UTC(),
	}
}

// checkCodeAgents performs health checks on all registered code agents.
func (h *HealthHandler) checkCodeAgents(ctx context.Context) map[string]CheckResult {
	results := make(map[string]CheckResult)

	providers := h.agentRegistry.Available()
	for _, provider := range providers {
		agent := h.agentRegistry.Get(provider)
		if agent == nil {
			continue
		}

		start := time.Now()
		available := agent.Available(ctx)
		latency := time.Since(start)

		msg := "available"
		if !available {
			msg = "unavailable"
		}

		results[string(provider)] = CheckResult{
			Healthy:   available,
			Message:   fmt.Sprintf("%s (%s)", msg, agent.Name()),
			Latency:   latency.String(),
			LastCheck: time.Now().UTC(),
		}
	}

	return results
}

// checkWorkExecutor checks whether the work executor is running.
func (h *HealthHandler) checkWorkExecutor() CheckResult {
	running := h.workExecutor.Running()
	msg := fmt.Sprintf("worker %s: running", h.workExecutor.WorkerID())
	if !running {
		msg = fmt.Sprintf("worker %s: stopped", h.workExecutor.WorkerID())
	}
	return CheckResult{
		Healthy:   running,
		Message:   msg,
		LastCheck: time.Now().UTC(),
	}
}

// checkRegistry checks whether the container registry is healthy.
func (h *HealthHandler) checkRegistry(ctx context.Context) CheckResult {
	status := h.registryChecker.Check(ctx)

	// Update metrics
	latencySeconds := 0.0
	if status.Latency != "" {
		// Parse duration string like "45ms"
		if d, err := time.ParseDuration(status.Latency); err == nil {
			latencySeconds = d.Seconds()
		}
	}
	metrics.SetRegistryHealth(status.Healthy, latencySeconds)

	result := CheckResult{
		Healthy:   status.Healthy,
		Latency:   status.Latency,
		LastCheck: status.LastChecked,
	}

	if status.Healthy {
		result.Message = "connected"
	} else {
		result.Message = status.Error
	}

	return result
}

// CheckResult represents the result of a health check.
type CheckResult struct {
	Healthy   bool      `json:"healthy"`
	Message   string    `json:"message"`
	Latency   string    `json:"latency,omitempty"`
	LastCheck time.Time `json:"last_check"`
}

// ReadinessResponse is the response for the /ready endpoint.
type ReadinessResponse struct {
	Status  string                 `json:"status"`
	Service string                 `json:"service"`
	Checks  map[string]CheckResult `json:"checks,omitempty"`
}

// CircuitsResponse is the response for the /health/circuits endpoint.
type CircuitsResponse struct {
	Circuits []circuitbreaker.StatusEntry `json:"circuits"`
}

// Circuits returns the status of all circuit breakers.
// GET /health/circuits
func (h *HealthHandler) Circuits(w http.ResponseWriter, r *http.Request) {
	entries := circuitbreaker.GlobalRegistry.AllStatus()
	api.WriteSuccess(w, r, CircuitsResponse{
		Circuits: entries,
	})
}