package intent

import (
	"os"
	"strings"
	"sync"
)

// V2DecisionTier 灰度切换的风险档位（由低到高逐步启用 V2 路由）
type V2DecisionTier string

const (
	V2TierNone       V2DecisionTier = "none"
	V2TierQuery      V2DecisionTier = "query"
	V2TierGenerate   V2DecisionTier = "generate"
	V2TierWriteLow   V2DecisionTier = "write_low"
	V2TierWriteHigh  V2DecisionTier = "write_high"
	V2TierAll        V2DecisionTier = "all"
)

// FeatureFlags Phase 5 意图识别灰度开关（环境变量覆盖，默认保守）
type FeatureFlags struct {
	IntentV2Shadow          bool
	IntentV2Decision        bool
	V2DecisionTier          V2DecisionTier
	WorkflowIntentsEnabled  bool
	MultiIntentEnabled      bool
	SemanticFallbackEnabled bool
}

var (
	flagsMu     sync.RWMutex
	activeFlags = defaultFeatureFlags()
)

func defaultFeatureFlags() FeatureFlags {
	return FeatureFlags{
		IntentV2Shadow:         envBool("INTENT_V2_SHADOW", false),
		IntentV2Decision:       envBool("INTENT_V2_DECISION", false),
		V2DecisionTier:         parseV2DecisionTier(os.Getenv("INTENT_V2_DECISION_TIER")),
		WorkflowIntentsEnabled: envBool("WORKFLOW_INTENTS_ENABLED", true),
		MultiIntentEnabled:     envBool("MULTI_INTENT_ENABLED", true),
		SemanticFallbackEnabled: envBool("SEMANTIC_FALLBACK_ENABLED", false),
	}
}

func parseV2DecisionTier(raw string) V2DecisionTier {
	switch strings.ToLower(strings.TrimSpace(raw)) {
	case "", "none":
		return V2TierNone
	case "query":
		return V2TierQuery
	case "generate":
		return V2TierGenerate
	case "write_low", "write-low", "low_write":
		return V2TierWriteLow
	case "write_high", "write-high", "high_write":
		return V2TierWriteHigh
	case "all":
		return V2TierAll
	default:
		return V2TierQuery
	}
}

func envBool(key string, def bool) bool {
	v := strings.TrimSpace(os.Getenv(key))
	if v == "" {
		return def
	}
	return v == "1" || strings.EqualFold(v, "true") || strings.EqualFold(v, "yes")
}

// CurrentFeatureFlags 返回当前生效的功能开关
func CurrentFeatureFlags() FeatureFlags {
	flagsMu.RLock()
	defer flagsMu.RUnlock()
	return activeFlags
}

// SetFeatureFlagsForTest 测试专用：临时覆盖开关
func SetFeatureFlagsForTest(f FeatureFlags) {
	flagsMu.Lock()
	activeFlags = f
	flagsMu.Unlock()
}

// ResetFeatureFlagsForTest 测试专用：恢复默认
func ResetFeatureFlagsForTest() {
	flagsMu.Lock()
	activeFlags = defaultFeatureFlags()
	flagsMu.Unlock()
}

// tierAllowsRisk 判断当前灰度档位是否允许该风险等级的 V2 路由
func tierAllowsRisk(tier V2DecisionTier, risk RiskLevel) bool {
	switch tier {
	case V2TierNone:
		return false
	case V2TierQuery:
		return risk == RiskLow
	case V2TierGenerate:
		return risk == RiskLow || risk == RiskMedium
	case V2TierWriteLow:
		return risk != RiskHigh
	case V2TierWriteHigh, V2TierAll:
		return true
	default:
		return false
	}
}