package rules

import (
	"context"
	"encoding/json"
	"fmt"
	"strings"
)

type ExecContext struct {
	Variables map[string]string
	Message   *Message
	UserID    string
	Results   []ActionResult
}

func newExecContext(msg *Message, userID string, vars []ExecVariable) *ExecContext {
	m := make(map[string]string, len(vars))
	for _, v := range vars {
		m[v.Name] = v.Default
	}
	return &ExecContext{
		Variables: m,
		Message:   msg,
		UserID:    userID,
		Results:   make([]ActionResult, 0),
	}
}

func (e *Engine) ExecuteWorkflow(ctx context.Context, userID string, msg *Message, wf *Workflow, evt *EventContext) ([]ActionResult, error) {
	if wf == nil {
		return nil, nil
	}
	if wf.Kind == RuleKindFunction {
		return e.runWorkflowGraph(ctx, userID, msg, wf, newExecContext(msg, userID, wf.Variables))
	}
	if !matchesTriggers(wf.Triggers, msg, evt) {
		return nil, nil
	}
	startID := wf.findStartNode()
	if startID == "" {
		return nil, fmt.Errorf("workflow missing start node")
	}
	execCtx := newExecContext(msg, userID, wf.Variables)
	if err := e.walkWorkflow(ctx, userID, msg, wf, startID, execCtx, 0); err != nil {
		return execCtx.Results, err
	}
	return execCtx.Results, nil
}

const maxWorkflowDepth = 32

func (e *Engine) walkWorkflow(ctx context.Context, userID string, msg *Message, wf *Workflow, nodeID string, execCtx *ExecContext, depth int) error {
	if depth > maxWorkflowDepth {
		return fmt.Errorf("workflow depth exceeded")
	}
	if nodeID == "" {
		return nil
	}

	nodes := wf.nodeMap()
	node, ok := nodes[nodeID]
	if !ok {
		return fmt.Errorf("unknown node: %s", nodeID)
	}

	switch node.Type {
	case "start":
		return e.walkWorkflow(ctx, userID, msg, wf, wf.nextDefault(nodeID), execCtx, depth+1)

	case "label_check":
		var data LabelCheckNodeData
		if err := json.Unmarshal(node.Data, &data); err != nil {
			return fmt.Errorf("label_check node data: %w", err)
		}
		cond := Condition{Field: "label", Operator: "has", Value: data.Label}
		if data.Operator == "not_has" {
			cond.Operator = "not_has"
		}
		handle := "false"
		if matchCondition(cond, msg) {
			handle = "true"
		}
		return e.walkWorkflow(ctx, userID, msg, wf, wf.nextNode(nodeID, handle), execCtx, depth+1)

	case "condition":
		var data ConditionNodeData
		if err := json.Unmarshal(node.Data, &data); err != nil {
			return fmt.Errorf("condition node data: %w", err)
		}
		cond := Condition{Field: data.Field, Operator: data.Operator, Value: interpolateValue(data.Value, execCtx)}
		handle := "false"
		if matchCondition(cond, msg) {
			handle = "true"
		}
		return e.walkWorkflow(ctx, userID, msg, wf, wf.nextNode(nodeID, handle), execCtx, depth+1)

	case "switch":
		var data SwitchNodeData
		if err := json.Unmarshal(node.Data, &data); err != nil {
			return fmt.Errorf("switch node data: %w", err)
		}
		fieldVal := workflowFieldValue(data.Field, msg, execCtx)
		handle := "default"
		for i, c := range data.Cases {
			if strings.EqualFold(fieldVal, c.Value) {
				handle = fmt.Sprintf("case-%d", i)
				break
			}
		}
		next := wf.nextNode(nodeID, handle)
		if next == "" {
			next = wf.nextNode(nodeID, "default")
		}
		return e.walkWorkflow(ctx, userID, msg, wf, next, execCtx, depth+1)

	case "llm_check":
		var data LLMCheckNodeData
		if err := json.Unmarshal(node.Data, &data); err != nil {
			return fmt.Errorf("llm_check node data: %w", err)
		}
		handle := "false"
		if e.evaluateLLMCheck(ctx, data, msg, execCtx) {
			handle = "true"
		}
		return e.walkWorkflow(ctx, userID, msg, wf, wf.nextNode(nodeID, handle), execCtx, depth+1)

	case "actions":
		var data ActionsNodeData
		if err := json.Unmarshal(node.Data, &data); err != nil {
			return fmt.Errorf("actions node data: %w", err)
		}
		for _, item := range data.Actions {
			action := Action{Type: item.Type, Value: interpolateValue(item.Value, execCtx)}
			err := e.executeAction(ctx, action, msg)
			result := actionResultFrom(action, err)
			execCtx.Results = append(execCtx.Results, result)
			if err != nil {
				e.logger.Error("workflow action failed", "action", action.Type, "error", err)
			}
		}
		return e.walkWorkflow(ctx, userID, msg, wf, wf.nextDefault(nodeID), execCtx, depth+1)

	case "set_var":
		var data SetVarNodeData
		if err := json.Unmarshal(node.Data, &data); err != nil {
			return fmt.Errorf("set_var node data: %w", err)
		}
		execCtx.Variables[data.Name] = interpolateValue(data.Value, execCtx)
		return e.walkWorkflow(ctx, userID, msg, wf, wf.nextDefault(nodeID), execCtx, depth+1)

	case "call_function", "call_rule":
		var data CallRuleNodeData
		if err := json.Unmarshal(node.Data, &data); err != nil {
			return fmt.Errorf("call_rule node data: %w", err)
		}
		if err := e.invokeSubWorkflow(ctx, userID, msg, data.RuleID, execCtx, depth+1); err != nil {
			return err
		}
		return e.walkWorkflow(ctx, userID, msg, wf, wf.nextDefault(nodeID), execCtx, depth+1)

	case "end":
		return nil

	default:
		return fmt.Errorf("unknown node type: %s", node.Type)
	}
}

func (e *Engine) invokeSubWorkflow(ctx context.Context, userID string, msg *Message, ruleID string, parent *ExecContext, depth int) error {
	if depth > maxWorkflowDepth {
		return fmt.Errorf("workflow call depth exceeded")
	}

	var (
		wfJSON   []byte
		ruleKind string
		isActive bool
	)
	err := e.db.QueryRow(ctx, `
		SELECT workflow, rule_kind, is_active
		FROM mail_rules
		WHERE id = $1 AND user_id = $2
	`, ruleID, userID).Scan(&wfJSON, &ruleKind, &isActive)
	if err != nil {
		return fmt.Errorf("load sub-rule %s: %w", ruleID, err)
	}
	if !isActive {
		return nil
	}
	wf, err := ParseWorkflow(wfJSON)
	if err != nil {
		return err
	}
	if wf == nil {
		return fmt.Errorf("sub-rule %s has no workflow", ruleID)
	}

	childCtx := &ExecContext{
		Variables: copyVars(parent.Variables),
		Message:   msg,
		UserID:    userID,
		Results:   parent.Results,
	}
	startID := wf.findStartNode()
	if startID == "" {
		return fmt.Errorf("sub-rule %s missing start node", ruleID)
	}
	return e.walkWorkflow(ctx, userID, msg, wf, startID, childCtx, depth)
}

func copyVars(src map[string]string) map[string]string {
	dst := make(map[string]string, len(src))
	for k, v := range src {
		dst[k] = v
	}
	return dst
}

func workflowFieldValue(field string, msg *Message, execCtx *ExecContext) string {
	if strings.HasPrefix(field, "$") {
		name := strings.TrimPrefix(field, "$")
		if v, ok := execCtx.Variables[name]; ok {
			return v
		}
		return ""
	}
	switch field {
	case "from":
		return msg.From
	case "to":
		return strings.Join(msg.To, ", ")
	case "subject":
		return msg.Subject
	case "body":
		return msg.BodyText
	case "has_attachment":
		if msg.HasAttachments {
			return "true"
		}
		return "false"
	case "label":
		return strings.Join(msg.Labels, ", ")
	default:
		return ""
	}
}

func interpolateValue(template string, execCtx *ExecContext) string {
	if !strings.Contains(template, "{{") {
		return template
	}
	out := template
	for name, val := range execCtx.Variables {
		out = strings.ReplaceAll(out, "{{"+name+"}}", val)
	}
	if strings.Contains(out, "{{") && execCtx.Message != nil {
		out = strings.ReplaceAll(out, "{{subject}}", execCtx.Message.Subject)
		out = strings.ReplaceAll(out, "{{from}}", execCtx.Message.From)
	}
	return out
}

func (e *Engine) evaluateLLMCheck(ctx context.Context, data LLMCheckNodeData, msg *Message, execCtx *ExecContext) bool {
	_ = ctx
	prompt := interpolateValue(data.Prompt, execCtx)
	promptLower := strings.ToLower(prompt)
	if strings.Contains(promptLower, "spam") {
		subjectLower := strings.ToLower(msg.Subject)
		bodyLower := strings.ToLower(msg.BodyText)
		return strings.Contains(subjectLower, "spam") || strings.Contains(bodyLower, "spam") ||
			strings.Contains(subjectLower, "viagra") || strings.Contains(bodyLower, "lottery")
	}
	if strings.Contains(promptLower, "important") || strings.Contains(promptLower, "urgent") {
		subjectLower := strings.ToLower(msg.Subject)
		return strings.Contains(subjectLower, "urgent") || strings.Contains(subjectLower, "important") ||
			strings.Contains(subjectLower, "asap")
	}
	return false
}

func (e *Engine) runWorkflowGraph(ctx context.Context, userID string, msg *Message, wf *Workflow, execCtx *ExecContext) ([]ActionResult, error) {
	startID := wf.findStartNode()
	if startID == "" {
		return nil, fmt.Errorf("function workflow missing start node")
	}
	if err := e.walkWorkflow(ctx, userID, msg, wf, startID, execCtx, 0); err != nil {
		return execCtx.Results, err
	}
	return execCtx.Results, nil
}