package rules

import (
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"time"

	"git.pengzhan.dev/haopengzhan/rsspipe/internal/models"
)

type Evaluator struct{}

func NewEvaluator() *Evaluator {
	return &Evaluator{}
}

// Evaluate checks whether a FeedEntry satisfies a Rule's conditions.
func (e *Evaluator) Evaluate(rule models.Rule, entry models.FeedEntry) bool {
	if len(rule.Conditions) == 0 {
		return true
	}

	matchMode := strings.ToLower(rule.MatchMode)
	if matchMode == "" || matchMode == "all" {
		for _, cond := range rule.Conditions {
			if !e.evaluateCondition(cond, entry) {
				return false
			}
		}
		return true
	}

	// matchMode == "any"
	for _, cond := range rule.Conditions {
		if e.evaluateCondition(cond, entry) {
			return true
		}
	}
	return false
}

func (e *Evaluator) evaluateCondition(cond models.RuleCondition, entry models.FeedEntry) bool {
	actualValue := e.resolveField(cond.Field, entry)
	return e.compare(actualValue, cond.Operator, cond.Value)
}

func (e *Evaluator) resolveField(field string, entry models.FeedEntry) interface{} {
	switch strings.ToLower(field) {
	case "feed_id":
		return entry.FeedID
	case "feed_title":
		return entry.FeedTitle
	case "title":
		return entry.Title
	case "author":
		return entry.Author
	case "url":
		return entry.URL
	case "content", "raw_content", "rss_content":
		if entry.Content != "" {
			return entry.Content
		}
		return entry.RawContent
	case "is_read":
		return entry.IsRead
	case "is_starred":
		return entry.IsStarred
	case "published_at":
		return entry.PublishedAt
	case "created_at":
		return entry.CreatedAt
	}

	// Variant field resolution: "variants.keywords", "variants.readability_full_text", "variants.tags"
	if strings.HasPrefix(field, "variants.") {
		variantKey := strings.TrimPrefix(field, "variants.")
		if entry.Variants != nil {
			if v, ok := entry.Variants[variantKey]; ok {
				return v.TextValue
			}
		}
	}

	return nil
}

func (e *Evaluator) compare(actual interface{}, op string, expected interface{}) bool {
	opLower := strings.ToLower(strings.TrimSpace(op))

	// Handle exists / not_exists operators
	if opLower == "exists" {
		if actual == nil {
			return false
		}
		if s, ok := actual.(string); ok && s == "" {
			return false
		}
		return true
	}
	if opLower == "not_exists" {
		if actual == nil {
			return true
		}
		if s, ok := actual.(string); ok && s == "" {
			return true
		}
		return false
	}

	if actual == nil {
		return opLower == "neq" || opLower == "!=" || opLower == "not_in" || opLower == "not_contains"
	}

	// Handle Time/Timestamp comparisons
	if actualTime, ok := actual.(time.Time); ok {
		return e.compareTime(actualTime, opLower, expected)
	}

	actualStr := fmt.Sprintf("%v", actual)
	expectedStr := fmt.Sprintf("%v", expected)

	switch opLower {
	case "eq", "==":
		return strings.EqualFold(actualStr, expectedStr)
	case "neq", "!=":
		return !strings.EqualFold(actualStr, expectedStr)
	case "contains":
		return strings.Contains(strings.ToLower(actualStr), strings.ToLower(expectedStr))
	case "not_contains":
		return !strings.Contains(strings.ToLower(actualStr), strings.ToLower(expectedStr))
	case "starts_with":
		return strings.HasPrefix(strings.ToLower(actualStr), strings.ToLower(expectedStr))
	case "ends_with":
		return strings.HasSuffix(strings.ToLower(actualStr), strings.ToLower(expectedStr))
	case "contains_any":
		tokens := parseStringList(expected)
		for _, token := range tokens {
			if strings.Contains(strings.ToLower(actualStr), strings.ToLower(token)) {
				return true
			}
		}
		return false
	case "in":
		tokens := parseStringList(expected)
		for _, item := range tokens {
			if strings.EqualFold(actualStr, item) {
				return true
			}
		}
		return false
	case "not_in":
		tokens := parseStringList(expected)
		for _, item := range tokens {
			if strings.EqualFold(actualStr, item) {
				return false
			}
		}
		return true
	case "matches", "regex":
		re, err := regexp.Compile(expectedStr)
		if err != nil {
			return false
		}
		return re.MatchString(actualStr)
	default:
		return false
	}
}

func (e *Evaluator) compareTime(t time.Time, op string, expected interface{}) bool {
	now := time.Now()
	switch op {
	case "within_last_hours":
		hours, err := toFloat64(expected)
		if err != nil {
			return false
		}
		cutoff := now.Add(-time.Duration(hours * float64(time.Hour)))
		return t.After(cutoff)
	case "older_than_days":
		days, err := toFloat64(expected)
		if err != nil {
			return false
		}
		cutoff := now.Add(-time.Duration(days * 24 * float64(time.Hour)))
		return t.Before(cutoff)
	case ">=", "after":
		targetTime, err := parseTime(expected)
		if err != nil {
			return false
		}
		return t.After(targetTime) || t.Equal(targetTime)
	case "<=", "before":
		targetTime, err := parseTime(expected)
		if err != nil {
			return false
		}
		return t.Before(targetTime) || t.Equal(targetTime)
	}
	return false
}

func parseStringList(val interface{}) []string {
	var result []string
	switch v := val.(type) {
	case []interface{}:
		for _, item := range v {
			result = append(result, strings.TrimSpace(fmt.Sprintf("%v", item)))
		}
	case []string:
		for _, item := range v {
			result = append(result, strings.TrimSpace(item))
		}
	case string:
		parts := strings.Split(v, ",")
		for _, part := range parts {
			trimmed := strings.TrimSpace(part)
			if trimmed != "" {
				result = append(result, trimmed)
			}
		}
	}
	return result
}

func toFloat64(val interface{}) (float64, error) {
	switch v := val.(type) {
	case float64:
		return v, nil
	case int:
		return float64(v), nil
	case int64:
		return float64(v), nil
	case string:
		return strconv.ParseFloat(strings.TrimSpace(v), 64)
	}
	return 0, fmt.Errorf("cannot convert %v to float64", val)
}

func parseTime(val interface{}) (time.Time, error) {
	if t, ok := val.(time.Time); ok {
		return t, nil
	}
	s := fmt.Sprintf("%v", val)
	return time.Parse(time.RFC3339, s)
}

// ValidateRuleSafety checks for potential cyclic/endless loops at rule creation time.
func ValidateRuleSafety(rule models.Rule) error {
	trigger := strings.ToLower(rule.Trigger)

	// If trigger is on_variant_updated / variant_change, check for recursive set_variant on same key
	if trigger == "on_variant_updated" || trigger == "variant_change" {
		for _, action := range rule.Actions {
			if action.Type == "set_variant" {
				targetKey, _ := action.Params["variant_key"].(string)
				if targetKey == "" {
					targetKey, _ = action.Params["key"].(string)
				}

				// Check if trigger targets this exact key without safe conditions
				for _, cond := range rule.Conditions {
					if cond.Field == "variants."+targetKey && (cond.Operator == "exists" || cond.Operator == "eq") {
						return fmt.Errorf("cyclic rule detected: rule triggers on variant '%s' and unconditionally writes to '%s'", targetKey, targetKey)
					}
				}
			}
		}
	}

	return nil
}