package automation

import (
	"context"
	"fmt"
	"regexp"
	"strings"

	"github.com/gochat/gochat/internal/model"
)

// ===========================
// Template Variable Resolution
// ===========================

// TemplateVariableResolver resolves {{variable}} placeholders in action params
// using conversation, contact, agent, and account context.
// Reference: Chatwoot liquid-style template variables — {{contact.name}}, {{conversation.status}}, etc.
// Chatwoot currently does NOT implement full liquid templating; gochat adds this as an extension
// per the M6 requirements doc section on CannedResponse variable interpolation.

// TemplateContext holds all the data needed to resolve template variables.
type TemplateContext struct {
	Conversation *model.Conversation
	Contact      *model.Contact
	Assignee     *model.User // the assigned agent (may be nil)
	Account      *model.Account
	Inbox        *model.Inbox
	Team         *model.Team // the assigned team (may be nil)
}

// templateVarRegex matches {{variable.name}} patterns.
var templateVarRegex = regexp.MustCompile(`\{\{(\w+)\.(\w+)\}\}`)

// ResolveTemplateVars replaces all {{object.attribute}} placeholders in a string
// with values from the provided TemplateContext.
// Unresolved variables are left as-is (not removed), matching Chatwoot behavior
// where unknown variables render as empty string rather than error.
func ResolveTemplateVars(input string, ctx TemplateContext) string {
	return templateVarRegex.ReplaceAllStringFunc(input, func(match string) string {
		parts := templateVarRegex.FindStringSubmatch(match)
		if len(parts) < 3 {
			return match // leave unresolved
		}
		object := parts[1]
		attribute := parts[2]

		value := resolveVariable(object, attribute, ctx)
		if value == "" {
			return "" // unresolved → empty string (Chatwoot convention)
		}
		return value
	})
}

// ResolveActionParams resolves template variables in all string values within
// an action's ActionParams map. This is the main integration point for ActionService.
// Returns nil if params is nil.
func ResolveActionParams(params map[string]interface{}, ctx TemplateContext) map[string]interface{} {
	if params == nil {
		return nil
	}
	resolved := make(map[string]interface{}, len(params))
	for key, val := range params {
		switch v := val.(type) {
		case string:
			resolved[key] = ResolveTemplateVars(v, ctx)
		default:
			resolved[key] = val // non-string values pass through unchanged
		}
	}
	return resolved
}

// resolveVariable resolves a single {{object.attribute}} reference.
func resolveVariable(object, attribute string, ctx TemplateContext) string {
	switch object {
	case "conversation":
		return resolveConversationAttr(attribute, ctx)
	case "contact":
		return resolveContactAttr(attribute, ctx)
	case "agent":
		return resolveAgentAttr(attribute, ctx)
	case "inbox":
		return resolveInboxAttr(attribute, ctx)
	case "team":
		return resolveTeamAttr(attribute, ctx)
	case "account":
		return resolveAccountAttr(attribute, ctx)
	default:
		return "" // unknown object → empty
	}
}

func resolveConversationAttr(attr string, ctx TemplateContext) string {
	if ctx.Conversation == nil {
		return ""
	}
	switch attr {
	case "status":
		return ctx.Conversation.Status
	case "priority":
		return ctx.Conversation.Priority
	case "channel_type":
		return ctx.Conversation.ChannelType
	case "display_id":
		if ctx.Conversation.DisplayID != nil {
			return fmt.Sprintf("%d", *ctx.Conversation.DisplayID)
		}
		return ""
	case "uuid":
		return ctx.Conversation.UUID
	case "id":
		return fmt.Sprintf("%d", ctx.Conversation.ID)
	default:
		return ""
	}
}

func resolveContactAttr(attr string, ctx TemplateContext) string {
	if ctx.Contact == nil {
		return ""
	}
	switch attr {
	case "name":
		return ctx.Contact.Name
	case "email":
		return ctx.Contact.Email
	case "phone_number":
		return ctx.Contact.PhoneNumber
	case "identifier":
		return ctx.Contact.Identifier
	case "country_code":
		return ctx.Contact.CountryCode
	case "location":
		return ctx.Contact.Location
	case "id":
		return fmt.Sprintf("%d", ctx.Contact.ID)
	default:
		return ""
	}
}

func resolveAgentAttr(attr string, ctx TemplateContext) string {
	if ctx.Assignee == nil {
		return ""
	}
	switch attr {
	case "name":
		return ctx.Assignee.Name
	case "email":
		return ctx.Assignee.Email
	case "id":
		return fmt.Sprintf("%d", ctx.Assignee.ID)
	case "role":
		return ctx.Assignee.Role
	default:
		return ""
	}
}

func resolveInboxAttr(attr string, ctx TemplateContext) string {
	if ctx.Inbox == nil {
		return ""
	}
	switch attr {
	case "name":
		return ctx.Inbox.Name
	case "channel_type":
		return ctx.Inbox.ChannelType
	case "id":
		return fmt.Sprintf("%d", ctx.Inbox.ID)
	default:
		return ""
	}
}

func resolveTeamAttr(attr string, ctx TemplateContext) string {
	if ctx.Team == nil {
		return ""
	}
	switch attr {
	case "name":
		return ctx.Team.Name
	case "id":
		return fmt.Sprintf("%d", ctx.Team.ID)
	default:
		return ""
	}
}

func resolveAccountAttr(attr string, ctx TemplateContext) string {
	if ctx.Account == nil {
		return ""
	}
	switch attr {
	case "name":
		return ctx.Account.Name
	case "id":
		return fmt.Sprintf("%d", ctx.Account.ID)
	default:
		return ""
	}
}

// ===========================
// Template Context Builder
// ===========================

// TemplateContextBuilder builds a TemplateContext by loading related entities
// from the database based on a conversation ID.
type TemplateContextBuilder struct {
	db DBProvider
}

// NewTemplateContextBuilder creates a new TemplateContextBuilder.
func NewTemplateContextBuilder(db DBProvider) *TemplateContextBuilder {
	return &TemplateContextBuilder{db: db}
}

// Build loads all related entities for a conversation and returns a TemplateContext.
func (b *TemplateContextBuilder) Build(ctx context.Context, conversationID uint) (TemplateContext, error) {
	db := b.db.DB().WithContext(ctx)

	// Load conversation
	var conv model.Conversation
	if err := db.First(&conv, conversationID).Error; err != nil {
		return TemplateContext{}, fmt.Errorf("failed to load conversation %d: %w", conversationID, err)
	}

	result := TemplateContext{
		Conversation: &conv,
	}

	// Load contact
	var contact model.Contact
	if err := db.First(&contact, conv.ContactID).Error; err != nil {
		// Contact not found is non-fatal; leave nil
		if !strings.Contains(err.Error(), "record not found") {
			return TemplateContext{}, fmt.Errorf("failed to load contact %d: %w", conv.ContactID, err)
		}
	} else {
		result.Contact = &contact
	}

	// Load assignee (agent)
	if conv.AssigneeID != nil && *conv.AssigneeID != 0 {
		var agent model.User
		if err := db.First(&agent, *conv.AssigneeID).Error; err != nil {
			// Assignee not found is non-fatal; leave nil
		} else {
			result.Assignee = &agent
		}
	}

	// Load inbox
	var inbox model.Inbox
	if err := db.First(&inbox, conv.InboxID).Error; err != nil {
		// Inbox not found is non-fatal; leave nil
	} else {
		result.Inbox = &inbox
	}

	// Load account
	var account model.Account
	if err := db.First(&account, conv.AccountID).Error; err != nil {
		// Account not found is non-fatal; leave nil
	} else {
		result.Account = &account
	}

	// Load team
	if conv.TeamID != nil && *conv.TeamID != 0 {
		var team model.Team
		if err := db.First(&team, *conv.TeamID).Error; err != nil {
			// Team not found is non-fatal; leave nil
		} else {
			result.Team = &team
		}
	}

	return result, nil
}