package rules

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"regexp"
	"strings"

	"github.com/jackc/pgx/v5/pgxpool"
	"github.com/ultisuite/ulti-backend/internal/mail/webhooks"
)

type WebhookExecutor interface {
	Execute(ctx context.Context, templateID string, msgCtx *webhooks.MessageContext) error
}

type Engine struct {
	db          *pgxpool.Pool
	logger      *slog.Logger
	webhookExec WebhookExecutor
}

func NewEngine(db *pgxpool.Pool) *Engine {
	return &Engine{
		db:     db,
		logger: slog.Default().With("component", "rules-engine"),
	}
}

func NewEngineWithWebhooks(db *pgxpool.Pool, webhookExec WebhookExecutor) *Engine {
	e := NewEngine(db)
	e.webhookExec = webhookExec
	return e
}

func (e *Engine) SetWebhookExecutor(webhookExec WebhookExecutor) {
	e.webhookExec = webhookExec
}

type Rule struct {
	ID         string      `json:"id"`
	Name       string      `json:"name"`
	Priority   int         `json:"priority"`
	Conditions []Condition `json:"conditions"`
	Actions    []Action    `json:"actions"`
}

type Condition struct {
	Field    string `json:"field"`    // from, to, subject, body, has_attachment
	Operator string `json:"operator"` // contains, equals, starts_with, ends_with, regex, has, not_has, ...
	Value    string `json:"value"`
}

type Action struct {
	Type  string `json:"type"`  // label, move, archive, delete, mark_read, forward, webhook
	Value string `json:"value"` // label name, folder name, email, webhook_id
}

type ActionResult struct {
	Type  string `json:"type"`
	Value string `json:"value"`
	OK    bool   `json:"ok"`
	Error string `json:"error"`
}

type Message struct {
	ID             string   `json:"id"`
	AccountID      string   `json:"account_id,omitempty"`
	FolderID       string   `json:"folder_id,omitempty"`
	From           string   `json:"from"`
	To             []string `json:"to"`
	Subject        string   `json:"subject"`
	BodyText       string   `json:"body_text"`
	HasAttachments bool     `json:"has_attachments"`
	Labels         []string `json:"labels,omitempty"`
}

func (e *Engine) Evaluate(ctx context.Context, userID string, msg *Message) error {
	return e.EvaluateMessage(ctx, userID, msg)
}

func (e *Engine) EvaluateMessage(ctx context.Context, userID string, msg *Message) error {
	return e.EvaluateMessageEvent(ctx, userID, msg, &EventContext{Type: TriggerMessageReceived})
}

func (e *Engine) EvaluateMessageEvent(ctx context.Context, userID string, msg *Message, evt *EventContext) error {
	rows, err := e.db.Query(ctx, `
		SELECT id, name, conditions, actions, workflow
		FROM mail_rules
		WHERE user_id = $1 AND is_active = true AND rule_kind = 'rule'
		ORDER BY priority ASC
	`, userID)
	if err != nil {
		return fmt.Errorf("query rules: %w", err)
	}
	defer rows.Close()

	for rows.Next() {
		var (
			ruleID   string
			name     string
			condJSON []byte
			actJSON  []byte
			wfJSON   []byte
		)
		if err := rows.Scan(&ruleID, &name, &condJSON, &actJSON, &wfJSON); err != nil {
			e.logger.Error("scan rule", "error", err)
			continue
		}

		wf, err := ParseWorkflow(wfJSON)
		if err != nil {
			e.logger.Error("parse workflow", "rule_id", ruleID, "error", err)
			continue
		}

		var results []ActionResult

		if wf != nil && len(wf.Nodes) > 0 {
			if !matchesTriggers(wf.Triggers, msg, evt) {
				continue
			}
			startID := wf.findStartNode()
			if startID == "" {
				e.logger.Error("workflow missing start", "rule_id", ruleID)
				continue
			}
			execCtx := newExecContext(msg, userID, wf.Variables)
			if err := e.walkWorkflow(ctx, userID, msg, wf, startID, execCtx, 0); err != nil {
				e.logger.Error("execute workflow", "rule_id", ruleID, "error", err)
			}
			results = execCtx.Results
		} else {
			var conditions []Condition
			var actions []Action
			json.Unmarshal(condJSON, &conditions)
			json.Unmarshal(actJSON, &actions)
			if !matchesAll(conditions, msg) {
				continue
			}
			results = e.executeRuleActions(ctx, ruleID, actions, msg)
		}

		e.logger.Info("rule matched", "rule_id", ruleID, "rule_name", name, "message_id", msg.ID)
		if err := e.recordRuleExecution(ctx, ruleID, msg.ID, results); err != nil {
			e.logger.Error("record rule execution", "rule_id", ruleID, "message_id", msg.ID, "error", err)
		}
		e.db.Exec(ctx, `UPDATE mail_rules SET match_count = match_count + 1 WHERE id = $1`, ruleID)
	}

	return nil
}

func (e *Engine) executeRuleActions(ctx context.Context, ruleID string, actions []Action, msg *Message) []ActionResult {
	results := make([]ActionResult, 0, len(actions))
	for _, action := range actions {
		err := e.executeAction(ctx, action, msg)
		results = append(results, actionResultFrom(action, err))
		if err != nil {
			e.logger.Error("action failed", "rule_id", ruleID, "action", action.Type, "error", err)
		}
	}
	return results
}

func actionResultFrom(action Action, err error) ActionResult {
	result := ActionResult{
		Type:  action.Type,
		Value: action.Value,
		OK:    err == nil,
	}
	if err != nil {
		result.Error = err.Error()
	}
	return result
}

func (e *Engine) recordRuleExecution(ctx context.Context, ruleID, messageID string, results []ActionResult) error {
	actionsJSON, err := json.Marshal(results)
	if err != nil {
		return fmt.Errorf("marshal actions_applied: %w", err)
	}

	execError := aggregateActionErrors(results)

	_, err = e.db.Exec(ctx, `
		INSERT INTO rule_executions (rule_id, message_id, actions_applied, error)
		VALUES ($1, $2, $3, $4)
	`, ruleID, messageID, actionsJSON, execError)
	if err != nil {
		return fmt.Errorf("insert rule_executions: %w", err)
	}
	return nil
}

func aggregateActionErrors(results []ActionResult) string {
	var parts []string
	for _, r := range results {
		if !r.OK && r.Error != "" {
			parts = append(parts, fmt.Sprintf("%s: %s", r.Type, r.Error))
		}
	}
	return strings.Join(parts, "; ")
}

func matchesAll(conditions []Condition, msg *Message) bool {
	for _, cond := range conditions {
		if !matchCondition(cond, msg) {
			return false
		}
	}
	return true
}

func matchCondition(cond Condition, msg *Message) bool {
	if cond.Field == "label" {
		has := messageHasLabel(msg, cond.Value)
		switch cond.Operator {
		case "has":
			return has
		case "not_has":
			return !has
		default:
			return false
		}
	}

	var fieldValue string
	switch cond.Field {
	case "from":
		fieldValue = msg.From
	case "to":
		fieldValue = strings.Join(msg.To, ", ")
	case "subject":
		fieldValue = msg.Subject
	case "body":
		fieldValue = msg.BodyText
	case "has_attachment":
		if msg.HasAttachments {
			fieldValue = "true"
		} else {
			fieldValue = "false"
		}
	default:
		return false
	}

	switch cond.Operator {
	case "regex":
		re, err := regexp.Compile(cond.Value)
		if err != nil {
			return false
		}
		return re.MatchString(fieldValue)
	case "not_regex":
		re, err := regexp.Compile(cond.Value)
		if err != nil {
			return false
		}
		return !re.MatchString(fieldValue)
	}

	fieldLower := strings.ToLower(fieldValue)
	valueLower := strings.ToLower(cond.Value)

	switch cond.Operator {
	case "contains":
		return strings.Contains(fieldLower, valueLower)
	case "equals":
		return fieldLower == valueLower
	case "starts_with":
		return strings.HasPrefix(fieldLower, valueLower)
	case "ends_with":
		return strings.HasSuffix(fieldLower, valueLower)
	case "not_contains":
		return !strings.Contains(fieldLower, valueLower)
	default:
		return false
	}
}

func messageHasLabel(msg *Message, label string) bool {
	labelLower := strings.ToLower(strings.TrimSpace(label))
	if labelLower == "" {
		return false
	}
	for _, l := range msg.Labels {
		if strings.ToLower(l) == labelLower {
			return true
		}
	}
	return false
}

func messageToWebhookContext(msg *Message) *webhooks.MessageContext {
	senderName, senderEmail := parseFromAddress(msg.From)
	return &webhooks.MessageContext{
		SenderName:    senderName,
		SenderEmail:   senderEmail,
		Subject:       msg.Subject,
		BodyText:      msg.BodyText,
		Recipients:    strings.Join(msg.To, ", "),
		HasAttachment: msg.HasAttachments,
		MessageID:     msg.ID,
	}
}

func parseFromAddress(from string) (name, email string) {
	from = strings.TrimSpace(from)
	if from == "" {
		return "", ""
	}
	if i := strings.LastIndex(from, "<"); i >= 0 {
		j := strings.LastIndex(from, ">")
		if j > i {
			email = strings.TrimSpace(from[i+1 : j])
			name = strings.TrimSpace(from[:i])
			name = strings.Trim(name, `"`)
			return name, email
		}
	}
	return "", from
}

func (e *Engine) executeAction(ctx context.Context, action Action, msg *Message) error {
	switch action.Type {
	case "label":
		_, err := e.db.Exec(ctx, `
			UPDATE messages SET labels = array_append(labels, $1), updated_at = NOW()
			WHERE id = $2 AND NOT ($1 = ANY(labels))
		`, action.Value, msg.ID)
		return err
	case "move":
		_, err := e.db.Exec(ctx, `
			UPDATE messages SET folder_id = (
				SELECT id FROM mail_folders WHERE account_id = (
					SELECT account_id FROM messages WHERE id = $2
				) AND name = $1 LIMIT 1
			), updated_at = NOW()
			WHERE id = $2
		`, action.Value, msg.ID)
		return err
	case "archive":
		_, err := e.db.Exec(ctx, `
			UPDATE messages SET flags = array_append(flags, '\Archive'), updated_at = NOW()
			WHERE id = $1
		`, msg.ID)
		return err
	case "mark_read":
		_, err := e.db.Exec(ctx, `
			UPDATE messages SET flags = array_append(flags, '\Seen'), updated_at = NOW()
			WHERE id = $1 AND NOT ('\Seen' = ANY(flags))
		`, msg.ID)
		return err
	case "delete":
		_, err := e.db.Exec(ctx, `
			UPDATE messages SET flags = array_append(flags, '\Deleted'), updated_at = NOW()
			WHERE id = $1
		`, msg.ID)
		return err
	case "remove_label":
		_, err := e.db.Exec(ctx, `
			UPDATE messages SET labels = array_remove(labels, $1), updated_at = NOW()
			WHERE id = $2
		`, action.Value, msg.ID)
		return err
	case "mark_important":
		_, err := e.db.Exec(ctx, `
			UPDATE messages SET flags = array_append(flags, '\Flagged'), updated_at = NOW()
			WHERE id = $1 AND NOT ('\Flagged' = ANY(flags))
		`, msg.ID)
		return err
	case "mark_spam":
		_, err := e.db.Exec(ctx, `
			UPDATE messages SET labels = (
				SELECT array_agg(DISTINCT x) FROM unnest(array_append(labels, 'SPAM')) AS x
			), updated_at = NOW()
			WHERE id = $1
		`, msg.ID)
		return err
	case "star":
		_, err := e.db.Exec(ctx, `
			UPDATE messages SET flags = array_append(flags, '\Flagged'), updated_at = NOW()
			WHERE id = $1 AND NOT ('\Flagged' = ANY(flags))
		`, msg.ID)
		return err
	case "notify":
		e.logger.Info("notification action", "message_id", msg.ID, "body", action.Value)
		return nil
	case "reply", "send_mail", "forward":
		e.logger.Info("deferred mail action", "type", action.Type, "message_id", msg.ID, "value", action.Value)
		return nil
	case "webhook":
		if e.webhookExec == nil {
			return fmt.Errorf("webhook executor not configured")
		}
		return e.webhookExec.Execute(ctx, action.Value, messageToWebhookContext(msg))
	default:
		return fmt.Errorf("unknown action type: %s", action.Type)
	}
}