package runner

import (
	"context"
	"errors"
	"net/http"
	"sort"
	"strings"
	"time"

	"github.com/easyai/easyai-ai-gateway/apps/api/internal/auth"
	"github.com/easyai/easyai-ai-gateway/apps/api/internal/clients"
	"github.com/easyai/easyai-ai-gateway/apps/api/internal/executionpool"
	"github.com/easyai/easyai-ai-gateway/apps/api/internal/netproxy"
	"github.com/easyai/easyai-ai-gateway/apps/api/internal/store"
)

const (
	routingVersion        = "execution-pool-v1"
	asyncRouteWaitMaximum = 10 * time.Second
)

func (s *Service) routingEnabled() bool {
	mode := strings.ToLower(strings.TrimSpace(s.cfg.RoutingMode))
	return mode == "shadow" || mode == "enforced"
}

func (s *Service) routingEnforced() bool {
	return strings.EqualFold(strings.TrimSpace(s.cfg.RoutingMode), "enforced")
}

func (s *Service) routeAsyncTask(ctx context.Context, task *store.GatewayTask, user *auth.User, preferred store.RuntimeModelCandidate) error {
	if task == nil || !task.AsyncMode || !s.routingEnabled() || task.RunMode == "simulation" {
		return nil
	}
	startedAt := time.Now()
	delays := []time.Duration{0, 2 * time.Second, 3 * time.Second, 4 * time.Second}
	var lastErr error
	for _, delay := range delays {
		if delay > 0 {
			timer := time.NewTimer(delay)
			select {
			case <-ctx.Done():
				if !timer.Stop() {
					<-timer.C
				}
				return ctx.Err()
			case <-timer.C:
			}
		}
		candidate := preferred
		if strings.TrimSpace(candidate.PlatformID) == "" {
			resolved, err := s.routingCandidateForTask(ctx, *task, user)
			if err != nil {
				lastErr = err
				continue
			}
			candidate = resolved
		}
		decision, profile, err := s.selectExecutionPool(ctx, *task, candidate)
		if err == nil {
			poolID := decision.PoolID
			snapshot := routingDecisionSnapshot(decision)
			if !s.routingEnforced() {
				s.observeExecutionPoolRouting("shadow")
				snapshot["suggestedPoolId"] = poolID
				poolID = ""
			}
			if s.routingEnforced() {
				s.observeExecutionPoolRouting("selected")
			}
			if err := s.store.AssignTaskRouting(ctx, store.TaskRoutingDecision{
				TaskID: task.ID, PoolID: poolID, RouteProfileKey: profile.Key,
				PlatformID: candidate.PlatformID, PlatformModelID: candidate.PlatformModelID,
				RoutingVersion: routingVersion, Reason: decision.Reason, Snapshot: snapshot,
			}); err != nil {
				return err
			}
			task.AssignedPoolID = poolID
			task.RouteProfileKey = profile.Key
			task.RoutingVersion = routingVersion
			task.RoutingReason = decision.Reason
			task.RoutingSnapshot = snapshot
			return nil
		}
		_ = s.coordinationStore.RequestRouteProbe(context.WithoutCancel(ctx), profile.Key)
		lastErr = err
		if !s.routingEnforced() {
			s.observeExecutionPoolRouting("shadow")
			_ = s.store.AssignTaskRouting(ctx, store.TaskRoutingDecision{
				TaskID: task.ID, RouteProfileKey: profile.Key, RoutingVersion: routingVersion,
				PlatformID: candidate.PlatformID, PlatformModelID: candidate.PlatformModelID,
				Reason: "shadow_no_eligible_pool", Snapshot: map[string]any{"mode": "shadow", "error": safeRoutingError(err)},
			})
			return nil
		}
	}
	s.observeExecutionPoolRouting("unavailable")
	if remaining := asyncRouteWaitMaximum - time.Since(startedAt); remaining > 0 {
		timer := time.NewTimer(remaining)
		select {
		case <-ctx.Done():
			if !timer.Stop() {
				<-timer.C
			}
			return ctx.Err()
		case <-timer.C:
		}
	}
	return upstreamRouteUnavailable(lastErr)
}

func (s *Service) observeExecutionPoolRouting(outcome string) {
	observer, ok := s.billingMetrics.(interface{ ObserveExecutionPoolRouting(string) })
	if ok {
		observer.ObserveExecutionPoolRouting(outcome)
	}
}

func (s *Service) routingCandidateForTask(ctx context.Context, task store.GatewayTask, user *auth.User) (store.RuntimeModelCandidate, error) {
	body := normalizeRequest(task.Kind, task.Request)
	modelType := modelTypeFromKind(task.Kind, body)
	candidates, err := s.store.ListModelCandidates(ctx, task.Model, modelType, user)
	if err != nil {
		return store.RuntimeModelCandidate{}, err
	}
	candidates, err = filterCandidatesByRequestedPlatform(candidates, body)
	if err == nil {
		candidates, _, err = filterRuntimeCandidatesByRequest(task.Kind, task.Model, modelType, body, candidates)
	}
	if err == nil {
		candidates, _, err = filterRuntimeCandidatesByOutputTokens(task.Kind, task.Model, modelType, body, candidates)
	}
	if err != nil {
		return store.RuntimeModelCandidate{}, err
	}
	if len(candidates) == 0 {
		return store.RuntimeModelCandidate{}, store.ErrNoModelCandidate
	}
	return candidates[0], nil
}

func (s *Service) selectExecutionPool(ctx context.Context, task store.GatewayTask, candidate store.RuntimeModelCandidate) (executionpool.Decision, executionpool.RouteProfile, error) {
	profile, err := routeProfileForCandidate(candidate)
	if err != nil {
		return executionpool.Decision{}, profile, err
	}
	now := time.Now()
	pools, err := s.coordinationStore.ListExecutionPools(ctx)
	if err != nil {
		return executionpool.Decision{}, profile, err
	}
	workers, err := s.coordinationStore.ListWorkers(ctx, now)
	if err != nil {
		return executionpool.Decision{}, profile, err
	}
	health, err := s.coordinationStore.ListRouteHealth(ctx, profile.Key, now)
	if err != nil {
		return executionpool.Decision{}, profile, err
	}
	capacity, err := s.coordinationStore.ListCapacity(ctx, now)
	if err != nil {
		return executionpool.Decision{}, profile, err
	}
	workersByPool := make(map[string][]executionpool.WorkerDescriptor)
	for _, worker := range workers {
		workersByPool[worker.PoolID] = append(workersByPool[worker.PoolID], worker)
	}
	healthByPool := make(map[string]executionpool.RouteHealth)
	for _, item := range health {
		healthByPool[item.PoolID] = item
	}
	capacityByPool := make(map[string]executionpool.CapacitySnapshot)
	for _, item := range capacity {
		capacityByPool[item.PoolID] = item
	}
	selection := make([]executionpool.SelectionCandidate, 0, len(pools))
	for _, pool := range pools {
		poolWorkers := workersByPool[pool.ID]
		selection = append(selection, executionpool.SelectionCandidate{
			Pool: pool, Health: healthByPool[pool.ID], Capacity: capacityByPool[pool.ID],
			CapabilityMatched: workerCapabilityMatched(poolWorkers, task),
		})
	}
	selector := executionpool.NewSelector()
	returnDecision, selectErr := selector.Select(executionpool.SelectionRequest{
		Candidates: selection, CurrentPoolID: task.AssignedPoolID, Now: now,
	})
	if selectErr != nil {
		return returnDecision, profile, selectErr
	}
	poolDecisions := make(map[string]executionpool.Decision, len(selection))
	scores := make(map[string]float64, len(selection))
	for _, candidate := range selection {
		decision, candidateErr := selector.Select(executionpool.SelectionRequest{Candidates: []executionpool.SelectionCandidate{candidate}, Now: now})
		if candidateErr == nil {
			poolDecisions[decision.PoolID] = decision
			scores[decision.PoolID] = decision.Score
		}
	}
	preference, err := s.coordinationStore.ResolveRoutePreference(ctx, profile.Key, returnDecision.PoolID, scores, now)
	if err != nil {
		return executionpool.Decision{}, profile, err
	}
	if preference.CurrentPoolID != returnDecision.PoolID {
		preferred, ok := poolDecisions[preference.CurrentPoolID]
		if !ok {
			return executionpool.Decision{}, profile, executionpool.ErrNoEligiblePool
		}
		preferred.Reason = "route_preference_hysteresis"
		preferred.Rejected = returnDecision.Rejected
		returnDecision = preferred
	}
	return returnDecision, profile, nil
}

func routeProfileForCandidate(candidate store.RuntimeModelCandidate) (executionpool.RouteProfile, error) {
	baseURL := routeEndpointForCandidate(candidate)
	host := executionpool.EndpointHost(baseURL)
	if host == "" {
		return executionpool.RouteProfile{}, errors.New("candidate does not expose a probeable upstream endpoint")
	}
	proxyMode := "none"
	if proxyConfig, err := netproxy.Normalize(netproxy.FromPlatformConfig(candidate.PlatformConfig)); err == nil {
		proxyMode = string(proxyConfig.Mode)
	}
	protocol := firstNonEmptyString(candidate.ResponseProtocol, candidate.SpecType, candidate.Provider)
	profile := executionpool.RouteProfile{
		Provider: candidate.Provider, Protocol: protocol, EndpointHost: host,
		ProxyMode: proxyMode, ConfigRevision: candidate.PlatformID + ":" + candidate.PlatformModelID,
	}
	profile.Key = executionpool.RouteProfileKey(profile.Provider, profile.Protocol, profile.EndpointHost, profile.ProxyMode, profile.ConfigRevision)
	return profile, nil
}

func routeEndpointForCandidate(candidate store.RuntimeModelCandidate) string {
	baseURL := strings.TrimSpace(candidate.BaseURL)
	if baseURL == "" {
		baseURL = firstString(candidate.PlatformConfig, "endpoint", "baseURL", "base_url")
	}
	return baseURL
}

func workerCapabilityMatched(workers []executionpool.WorkerDescriptor, task store.GatewayTask) bool {
	for _, worker := range workers {
		if worker.ProtocolVersion != executionpool.ProtocolVersion || worker.AvailableCapacity() < 1 {
			continue
		}
		if requestStreamEnabled(task.Request) && !boolValue(worker.Capabilities["streaming"]) {
			continue
		}
		if !workerSupportsTaskKind(worker.Capabilities["taskKinds"], task.Kind) {
			continue
		}
		return true
	}
	return false
}

func workerSupportsTaskKind(raw any, taskKind string) bool {
	taskKind = strings.ToLower(strings.TrimSpace(taskKind))
	if taskKind == "" {
		return false
	}
	values, ok := raw.([]any)
	if !ok {
		if stringsList, stringsOK := raw.([]string); stringsOK {
			values = make([]any, 0, len(stringsList))
			for _, value := range stringsList {
				values = append(values, value)
			}
		}
	}
	for _, value := range values {
		capability, _ := value.(string)
		capability = strings.ToLower(strings.TrimSpace(capability))
		if capability == "*" || capability == taskKind ||
			(strings.HasSuffix(capability, ".*") && strings.HasPrefix(taskKind, strings.TrimSuffix(capability, "*"))) {
			return true
		}
	}
	return false
}

func requestStreamEnabled(body map[string]any) bool {
	value, _ := body["stream"].(bool)
	return value
}

func routingDecisionSnapshot(decision executionpool.Decision) map[string]any {
	rejected := make([]string, 0, len(decision.Rejected))
	for poolID, reason := range decision.Rejected {
		rejected = append(rejected, poolID+":"+reason)
	}
	sort.Strings(rejected)
	return map[string]any{
		"mode": "selected", "score": decision.Score, "components": decision.Components,
		"rejected": rejected,
	}
}

func safeRoutingError(err error) string {
	if errors.Is(err, executionpool.ErrNoEligiblePool) {
		return "no_eligible_pool"
	}
	return "routing_unavailable"
}

func upstreamRouteUnavailable(cause error) error {
	details := map[string]any{"retryAfterSeconds": 10}
	if cause != nil {
		details["reason"] = safeRoutingError(cause)
	}
	return &clients.ClientError{
		Code: "upstream_route_unavailable", Message: "no execution pool can currently reach the upstream route",
		Retryable: true, StatusCode: http.StatusServiceUnavailable, Details: details,
	}
}

func firstString(values map[string]any, keys ...string) string {
	for _, key := range keys {
		if value, ok := values[key].(string); ok && strings.TrimSpace(value) != "" {
			return strings.TrimSpace(value)
		}
	}
	return ""
}

func boolValue(value any) bool {
	result, _ := value.(bool)
	return result
}