package service

import (
	"context"
	"fmt"
	"math"
	"strconv"
	"strings"
	"time"

	"github.com/gochat/gochat/internal/model"
	"github.com/gochat/gochat/internal/repository"
	applogger "github.com/gochat/gochat/pkg/logger"
	pkgvalidator "github.com/gochat/gochat/pkg/validator"
	"gorm.io/gorm"
)

const appliedSlaReportPageSize = 25

// SlaPolicyService implements business logic for SLA Policy operations.
// Reference: Chatwoot app/controllers/api/v1/sla_policies_controller.rb
type SlaPolicyService struct {
	slaPolicyRepo      *repository.SlaPolicyRepo
	appliedSlaRepo     *repository.AppliedSlaRepo
	slaEventRepo       *repository.SlaEventRepo
	slaPolicyInboxRepo *repository.SlaPolicyInboxRepo
}

// NewSlaPolicyService creates a new SlaPolicy service.
func NewSlaPolicyService(
	slaPolicyRepo *repository.SlaPolicyRepo,
	appliedSlaRepo *repository.AppliedSlaRepo,
	slaEventRepo *repository.SlaEventRepo,
	slaPolicyInboxRepo *repository.SlaPolicyInboxRepo,
) *SlaPolicyService {
	return &SlaPolicyService{
		slaPolicyRepo:      slaPolicyRepo,
		appliedSlaRepo:     appliedSlaRepo,
		slaEventRepo:       slaEventRepo,
		slaPolicyInboxRepo: slaPolicyInboxRepo,
	}
}

// DB returns the underlying gorm.DB for Chatwoot report serializers.
func (s *SlaPolicyService) DB() *gorm.DB {
	if s == nil || s.appliedSlaRepo == nil {
		return nil
	}
	return s.appliedSlaRepo.DB()
}

// CreateSlaPolicyRequest is the DTO for creating a SLA policy.
// Reference: Chatwoot sla_policies_controller.rb#permitted_params — nested under "sla_policy" key
// Fields: name, description, first_response_time_threshold, next_response_time_threshold,
// resolution_time_threshold, only_during_business_hours
type CreateSlaPolicyRequest struct {
	Name                       string `json:"name" validate:"required"`
	Description                string `json:"description,omitempty"`
	FirstResponseTimeThreshold int    `json:"first_response_time_threshold" validate:"min=0"`
	NextResponseTimeThreshold  int    `json:"next_response_time_threshold" validate:"min=0"`
	ResolutionTimeThreshold    int    `json:"resolution_time_threshold" validate:"min=0"`
	OnlyDuringBusinessHours    bool   `json:"only_during_business_hours"`
}

// SlaPolicyCreateWrapper wraps CreateSlaPolicyRequest under the "sla_policy" JSON key.
// Chatwoot requires params.require(:sla_policy), so the request body must be:
// { "sla_policy": { "name": "...", "first_response_time_threshold": 60, ... } }
type SlaPolicyCreateWrapper struct {
	SlaPolicy CreateSlaPolicyRequest `json:"sla_policy"`
}

// UpdateSlaPolicyRequest is the DTO for updating a SLA policy.
// Reference: same permitted_params as Create, all optional for update
type UpdateSlaPolicyRequest struct {
	Name                       string `json:"name,omitempty"`
	Description                string `json:"description,omitempty"`
	FirstResponseTimeThreshold *int   `json:"first_response_time_threshold,omitempty" validate:"omitempty,min=0"`
	NextResponseTimeThreshold  *int   `json:"next_response_time_threshold,omitempty" validate:"omitempty,min=0"`
	ResolutionTimeThreshold    *int   `json:"resolution_time_threshold,omitempty" validate:"omitempty,min=0"`
	OnlyDuringBusinessHours    *bool  `json:"only_during_business_hours,omitempty"`
}

// SlaPolicyUpdateWrapper wraps UpdateSlaPolicyRequest under the "sla_policy" JSON key.
type SlaPolicyUpdateWrapper struct {
	SlaPolicy UpdateSlaPolicyRequest `json:"sla_policy"`
}

// AppliedSlaReportFilter mirrors Chatwoot AppliedSlasController report filters.
type AppliedSlaReportFilter struct {
	Since           *time.Time
	Until           *time.Time
	InboxID         *uint
	TeamID          *uint
	SlaPolicyID     *uint
	LabelList       string
	AssignedAgentID *uint
	SLAStatus       string
}

// AppliedSlaReportResult is the paginated Chatwoot applied_slas#index result.
type AppliedSlaReportResult struct {
	AppliedSLAs []model.AppliedSLA
	Count       int64
	CurrentPage int
}

// AppliedSlaMetricsResult is the Chatwoot applied_slas#metrics payload.
type AppliedSlaMetricsResult struct {
	TotalAppliedSlas  int64  `json:"total_applied_slas"`
	NumberOfSlaMisses int64  `json:"number_of_sla_misses"`
	HitRate           string `json:"hit_rate"`
}

// Create creates a new SLA policy for an account.
func (s *SlaPolicyService) Create(ctx context.Context, accountID uint, req *CreateSlaPolicyRequest) (*model.SlaPolicy, error) {
	if err := pkgvalidator.ValidateStruct(req); err != nil {
		return nil, fmt.Errorf("validation error: %w", err)
	}

	policy := &model.SlaPolicy{
		AccountID:                  accountID,
		Name:                       req.Name,
		Description:                req.Description,
		FirstResponseTimeThreshold: req.FirstResponseTimeThreshold,
		NextResponseTimeThreshold:  req.NextResponseTimeThreshold,
		ResolutionTimeThreshold:    req.ResolutionTimeThreshold,
		OnlyDuringBusinessHours:    req.OnlyDuringBusinessHours,
	}

	if err := s.slaPolicyRepo.Create(ctx, policy); err != nil {
		return nil, fmt.Errorf("create sla policy: %w", err)
	}

	applogger.L().Infof("SLA policy %d created for account %d", policy.ID, accountID)
	return policy, nil
}

// Get retrieves a SLA policy by ID.
func (s *SlaPolicyService) Get(ctx context.Context, accountID, policyID uint) (*model.SlaPolicy, error) {
	policy, err := s.slaPolicyRepo.FindByID(ctx, policyID)
	if err != nil {
		return nil, fmt.Errorf("sla policy not found: %w", err)
	}
	if policy.AccountID != accountID {
		return nil, fmt.Errorf("sla policy %d does not belong to account %d", policyID, accountID)
	}
	return policy, nil
}

// List retrieves all SLA policies for an account.
func (s *SlaPolicyService) List(ctx context.Context, accountID uint) ([]model.SlaPolicy, error) {
	return s.slaPolicyRepo.FindByAccount(ctx, accountID)
}

// Update updates a SLA policy.
func (s *SlaPolicyService) Update(ctx context.Context, accountID, policyID uint, req *UpdateSlaPolicyRequest) (*model.SlaPolicy, error) {
	policy, err := s.Get(ctx, accountID, policyID)
	if err != nil {
		return nil, err
	}

	if req.Name != "" {
		policy.Name = req.Name
	}
	if req.Description != "" {
		policy.Description = req.Description
	}
	if req.FirstResponseTimeThreshold != nil {
		policy.FirstResponseTimeThreshold = *req.FirstResponseTimeThreshold
	}
	if req.NextResponseTimeThreshold != nil {
		policy.NextResponseTimeThreshold = *req.NextResponseTimeThreshold
	}
	if req.ResolutionTimeThreshold != nil {
		policy.ResolutionTimeThreshold = *req.ResolutionTimeThreshold
	}
	if req.OnlyDuringBusinessHours != nil {
		policy.OnlyDuringBusinessHours = *req.OnlyDuringBusinessHours
	}

	if err := s.slaPolicyRepo.Update(ctx, policy); err != nil {
		return nil, fmt.Errorf("update sla policy: %w", err)
	}

	applogger.L().Infof("SLA policy %d updated for account %d", policyID, accountID)
	return policy, nil
}

// Delete deletes a SLA policy (and its inbox associations).
func (s *SlaPolicyService) Delete(ctx context.Context, accountID, policyID uint) error {
	policy, err := s.Get(ctx, accountID, policyID)
	if err != nil {
		return err
	}

	// Remove all inbox associations first
	if err := s.slaPolicyInboxRepo.DeleteBySlaPolicy(ctx, policy.ID); err != nil {
		return fmt.Errorf("delete inbox associations: %w", err)
	}

	if err := s.slaPolicyRepo.Delete(ctx, policy.ID); err != nil {
		return fmt.Errorf("delete sla policy: %w", err)
	}

	applogger.L().Infof("SLA policy %d deleted for account %d", policyID, accountID)
	return nil
}

// GetAppliedSlaMetrics retrieves SLA metrics for a conversation.
// Returns the applied SLA and its events.
func (s *SlaPolicyService) GetAppliedSlaMetrics(ctx context.Context, accountID, conversationID uint) (*model.AppliedSLA, []model.SlaEvent, error) {
	applied, err := s.appliedSlaRepo.FindByConversation(ctx, conversationID)
	if err != nil {
		return nil, nil, fmt.Errorf("applied sla not found: %w", err)
	}
	if applied.AccountID != accountID {
		return nil, nil, fmt.Errorf("applied sla does not belong to account %d", accountID)
	}

	events, err := s.slaEventRepo.FindByAppliedSla(ctx, applied.ID)
	if err != nil {
		return nil, nil, fmt.Errorf("sla events not found: %w", err)
	}

	return applied, events, nil
}

// GetAppliedSlaDownload retrieves all applied SLAs for an account (for export/download).
func (s *SlaPolicyService) GetAppliedSlaDownload(ctx context.Context, accountID uint) ([]model.AppliedSLA, error) {
	return s.appliedSlaRepo.FindByAccount(ctx, accountID)
}

// ListAppliedSlaReports returns missed applied SLAs for the account report table.
func (s *SlaPolicyService) ListAppliedSlaReports(ctx context.Context, accountID uint, filter AppliedSlaReportFilter, page int) (*AppliedSlaReportResult, error) {
	if page < 1 {
		page = 1
	}
	repoFilter := toRepoAppliedSlaReportFilter(filter)
	offset := (page - 1) * appliedSlaReportPageSize
	applied, count, err := s.appliedSlaRepo.FindReport(ctx, accountID, repoFilter, true, offset, appliedSlaReportPageSize)
	if err != nil {
		return nil, fmt.Errorf("list applied sla reports: %w", err)
	}
	return &AppliedSlaReportResult{AppliedSLAs: applied, Count: count, CurrentPage: page}, nil
}

// GetAppliedSlaReportMetrics returns metrics for the filtered applied SLA set.
func (s *SlaPolicyService) GetAppliedSlaReportMetrics(ctx context.Context, accountID uint, filter AppliedSlaReportFilter) (*AppliedSlaMetricsResult, error) {
	total, missed, err := s.appliedSlaRepo.CountReport(ctx, accountID, toRepoAppliedSlaReportFilter(filter))
	if err != nil {
		return nil, fmt.Errorf("count applied sla reports: %w", err)
	}
	return &AppliedSlaMetricsResult{
		TotalAppliedSlas:  total,
		NumberOfSlaMisses: missed,
		HitRate:           formatAppliedSlaHitRate(total, missed),
	}, nil
}

// ListAppliedSlaReportDownload returns all filtered missed applied SLAs for CSV export.
func (s *SlaPolicyService) ListAppliedSlaReportDownload(ctx context.Context, accountID uint, filter AppliedSlaReportFilter) ([]model.AppliedSLA, error) {
	applied, _, err := s.appliedSlaRepo.FindReport(ctx, accountID, toRepoAppliedSlaReportFilter(filter), true, 0, 0)
	if err != nil {
		return nil, fmt.Errorf("download applied sla reports: %w", err)
	}
	return applied, nil
}

func toRepoAppliedSlaReportFilter(filter AppliedSlaReportFilter) repository.AppliedSlaReportFilter {
	return repository.AppliedSlaReportFilter{
		Since:           filter.Since,
		Until:           filter.Until,
		InboxID:         filter.InboxID,
		TeamID:          filter.TeamID,
		SlaPolicyID:     filter.SlaPolicyID,
		LabelList:       filter.LabelList,
		AssignedAgentID: filter.AssignedAgentID,
		SLAStatus:       filter.SLAStatus,
	}
}

func formatAppliedSlaHitRate(total, missed int64) string {
	if missed == 0 || total == 0 {
		return "100%"
	}
	rate := float64(total-missed) / float64(total) * 100
	rate = math.Round(rate*100) / 100
	formatted := strconv.FormatFloat(rate, 'f', 2, 64)
	formatted = strings.TrimRight(formatted, "0")
	if strings.HasSuffix(formatted, ".") {
		formatted += "0"
	}
	return formatted + "%"
}

// ListInboxes retrieves all inboxes associated with a SLA policy.
func (s *SlaPolicyService) ListInboxes(ctx context.Context, accountID, policyID uint) ([]model.SlaPolicyInbox, error) {
	policy, err := s.Get(ctx, accountID, policyID)
	if err != nil {
		return nil, err
	}
	return s.slaPolicyInboxRepo.FindBySlaPolicy(ctx, policy.ID)
}

// AddInbox associates an inbox with a SLA policy.
func (s *SlaPolicyService) AddInbox(ctx context.Context, accountID, policyID, inboxID uint) (*model.SlaPolicyInbox, error) {
	policy, err := s.Get(ctx, accountID, policyID)
	if err != nil {
		return nil, err
	}

	spi := &model.SlaPolicyInbox{
		SlaPolicyID: policy.ID,
		InboxID:     inboxID,
		AccountID:   accountID,
	}
	if err := s.slaPolicyInboxRepo.Create(ctx, spi); err != nil {
		return nil, fmt.Errorf("add inbox to sla policy: %w", err)
	}

	applogger.L().Infof("Inbox %d added to SLA policy %d", inboxID, policyID)
	return spi, nil
}

// RemoveInbox removes an inbox association from a SLA policy.
func (s *SlaPolicyService) RemoveInbox(ctx context.Context, accountID, policyID, inboxID uint) error {
	policy, err := s.Get(ctx, accountID, policyID)
	if err != nil {
		return err
	}

	spInboxes, err := s.slaPolicyInboxRepo.FindBySlaPolicy(ctx, policy.ID)
	if err != nil {
		return fmt.Errorf("find inbox associations: %w", err)
	}

	for _, spi := range spInboxes {
		if spi.InboxID == inboxID {
			if err := s.slaPolicyInboxRepo.Delete(ctx, spi.ID); err != nil {
				return fmt.Errorf("remove inbox from sla policy: %w", err)
			}
			applogger.L().Infof("Inbox %d removed from SLA policy %d", inboxID, policyID)
			return nil
		}
	}

	return fmt.Errorf("inbox %d not associated with sla policy %d", inboxID, policyID)
}