package message

import (
	"context"
	"encoding/json"
	"fmt"
	"slices"
	"sort"
	"strings"
	"time"

	"hyapp/pkg/appcode"
	"hyapp/pkg/xerr"
	messagedomain "hyapp/services/activity-service/internal/domain/message"
)

const (
	defaultFanoutPollInterval = time.Second
	defaultFanoutLockTTL      = 30 * time.Second
	defaultFanoutMaxRetry     = 8
	fanoutProducer            = "message-fanout"
	fanoutProducerEventType   = "message_fanout"
)

// FanoutWorkerOptions carries runtime knobs for the durable fanout worker.
type FanoutWorkerOptions struct {
	WorkerID     string
	PollInterval time.Duration
	LockTTL      time.Duration
	BatchSize    int
	MaxRetry     int
}

type fanoutTargetFilter struct {
	TargetUserID int64   `json:"target_user_id"`
	UserID       int64   `json:"user_id"`
	UserIDs      []int64 `json:"user_ids"`
	RegionID     int64   `json:"region_id"`
	Country      string  `json:"country"`
}

type fanoutTemplateSnapshot struct {
	ProducerEventType string          `json:"producer_event_type"`
	AggregateType     string          `json:"aggregate_type"`
	AggregateID       string          `json:"aggregate_id"`
	TemplateID        string          `json:"template_id"`
	TemplateVersion   string          `json:"template_version"`
	Title             string          `json:"title"`
	Summary           string          `json:"summary"`
	Body              string          `json:"body"`
	IconURL           string          `json:"icon_url"`
	ImageURL          string          `json:"image_url"`
	ActionType        string          `json:"action_type"`
	ActionParam       string          `json:"action_param"`
	Priority          int32           `json:"priority"`
	SentAtMS          int64           `json:"sent_at_ms"`
	ExpireAtMS        int64           `json:"expire_at_ms"`
	MetadataJSON      json.RawMessage `json:"metadata_json"`
}

// ProcessNextFanoutJob claims one job, processes one target page, then commits progress.
func (s *Service) ProcessNextFanoutJob(ctx context.Context, options FanoutWorkerOptions) (bool, error) {
	if err := s.requireRepository(); err != nil {
		return false, err
	}
	options = normalizeFanoutWorkerOptions(options, s.cfg.NodeID)
	nowMS := s.now().UnixMilli()
	job, claimed, err := s.repository.ClaimFanoutJob(ctx, options.WorkerID, nowMS, nowMS+options.LockTTL.Milliseconds(), options.MaxRetry)
	if err != nil || !claimed {
		return claimed, err
	}

	jobCtx := appcode.WithContext(ctx, job.AppCode)
	progress, processErr := s.processFanoutJobPage(jobCtx, job, options)
	if processErr != nil {
		failErr := s.repository.FailFanoutJob(jobCtx, job.JobID, options.WorkerID, nowMS, nowMS+options.PollInterval.Milliseconds(), options.MaxRetry, processErr.Error())
		if failErr != nil {
			return true, failErr
		}
		return true, processErr
	}
	if err := s.repository.FinishFanoutJobBatch(jobCtx, job.JobID, options.WorkerID, progress.nextCursorUserID, progress.totalDelta, progress.successDelta, progress.failureDelta, progress.done, nowMS, progress.errorMessage); err != nil {
		return true, err
	}
	return true, nil
}

type fanoutProgress struct {
	nextCursorUserID int64
	totalDelta       int64
	successDelta     int64
	failureDelta     int64
	done             bool
	errorMessage     string
}

func (s *Service) processFanoutJobPage(ctx context.Context, job messagedomain.FanoutJob, options FanoutWorkerOptions) (fanoutProgress, error) {
	var target fanoutTargetFilter
	if err := json.Unmarshal([]byte(job.TargetFilterJSON), &target); err != nil {
		return fanoutProgress{}, xerr.New(xerr.InvalidArgument, "target_filter_json is invalid")
	}
	var snapshot fanoutTemplateSnapshot
	if err := json.Unmarshal([]byte(job.TemplateSnapshotJSON), &snapshot); err != nil {
		return fanoutProgress{}, xerr.New(xerr.InvalidArgument, "template_snapshot_json is invalid")
	}
	pageSize := int(normalizeBatchSize(firstPositiveInt32(job.BatchSize, int32(options.BatchSize))))
	userIDs, nextCursor, done, err := s.fanoutTargetPage(ctx, job, target, pageSize)
	if err != nil {
		return fanoutProgress{}, err
	}
	progress := fanoutProgress{nextCursorUserID: nextCursor, totalDelta: int64(len(userIDs)), done: done}
	for _, userID := range userIDs {
		_, _, err := s.CreateInboxMessage(ctx, messagedomain.CreateInput{
			TargetUserID:      userID,
			Producer:          fanoutProducer,
			ProducerEventID:   fmt.Sprintf("fanout:%s:%d", job.JobID, userID),
			ProducerEventType: firstNonEmpty(snapshot.ProducerEventType, fanoutProducerEventType),
			MessageType:       job.MessageType,
			AggregateType:     snapshot.AggregateType,
			AggregateID:       snapshot.AggregateID,
			TemplateID:        snapshot.TemplateID,
			TemplateVersion:   snapshot.TemplateVersion,
			Title:             snapshot.Title,
			Summary:           snapshot.Summary,
			Body:              snapshot.Body,
			IconURL:           snapshot.IconURL,
			ImageURL:          snapshot.ImageURL,
			ActionType:        snapshot.ActionType,
			ActionParam:       snapshot.ActionParam,
			Priority:          snapshot.Priority,
			SentAtMS:          snapshot.SentAtMS,
			ExpireAtMS:        snapshot.ExpireAtMS,
			MetadataJSON:      rawJSONToString(snapshot.MetadataJSON),
		})
		if err != nil {
			return fanoutProgress{}, err
		}
		progress.successDelta++
	}
	return progress, nil
}

func (s *Service) fanoutTargetPage(ctx context.Context, job messagedomain.FanoutJob, target fanoutTargetFilter, pageSize int) ([]int64, int64, bool, error) {
	switch job.TargetScope {
	case messagedomain.TargetScopeSingleUser:
		userID := firstPositive(target.TargetUserID, target.UserID)
		if userID <= 0 {
			return nil, job.CursorUserID, false, xerr.New(xerr.InvalidArgument, "target_user_id is required")
		}
		if job.CursorUserID >= userID {
			return nil, job.CursorUserID, true, nil
		}
		return []int64{userID}, userID, true, nil
	case messagedomain.TargetScopeUserIDs:
		return userIDsTargetPage(target.UserIDs, job.CursorUserID, pageSize)
	case messagedomain.TargetScopeRegion, messagedomain.TargetScopeCountry, messagedomain.TargetScopeAllActiveUsers:
		if s.targetSource == nil {
			return nil, job.CursorUserID, false, xerr.New(xerr.Unavailable, "fanout target source is not configured")
		}
		return s.targetSource.ListFanoutUserIDs(ctx, TargetQuery{
			TargetScope:  job.TargetScope,
			CursorUserID: job.CursorUserID,
			PageSize:     pageSize,
			RegionID:     target.RegionID,
			Country:      target.Country,
		})
	default:
		return nil, job.CursorUserID, false, xerr.New(xerr.InvalidArgument, "target_scope is invalid")
	}
}

func userIDsTargetPage(userIDs []int64, cursorUserID int64, pageSize int) ([]int64, int64, bool, error) {
	unique := make([]int64, 0, len(userIDs))
	seen := make(map[int64]bool, len(userIDs))
	for _, userID := range userIDs {
		if userID <= 0 {
			return nil, cursorUserID, false, xerr.New(xerr.InvalidArgument, "user_ids contains invalid value")
		}
		if !seen[userID] {
			seen[userID] = true
			unique = append(unique, userID)
		}
	}
	slices.Sort(unique)
	start := sort.Search(len(unique), func(i int) bool { return unique[i] > cursorUserID })
	if start >= len(unique) {
		return nil, cursorUserID, true, nil
	}
	end := min(start+pageSize, len(unique))
	page := append([]int64(nil), unique[start:end]...)
	return page, page[len(page)-1], end >= len(unique), nil
}

func normalizeFanoutWorkerOptions(options FanoutWorkerOptions, defaultWorkerID string) FanoutWorkerOptions {
	options.WorkerID = strings.TrimSpace(options.WorkerID)
	if options.WorkerID == "" {
		options.WorkerID = firstNonEmpty(defaultWorkerID, "activity-fanout-worker")
	}
	if options.PollInterval <= 0 {
		options.PollInterval = defaultFanoutPollInterval
	}
	if options.LockTTL <= 0 {
		options.LockTTL = defaultFanoutLockTTL
	}
	if options.BatchSize <= 0 {
		options.BatchSize = defaultBatchSize
	}
	if options.MaxRetry <= 0 {
		options.MaxRetry = defaultFanoutMaxRetry
	}
	return options
}

func rawJSONToString(raw json.RawMessage) string {
	raw = json.RawMessage([]byte(strings.TrimSpace(string(raw))))
	if len(raw) == 0 || string(raw) == "null" {
		return ""
	}
	var text string
	if err := json.Unmarshal(raw, &text); err == nil {
		return strings.TrimSpace(text)
	}
	return string(raw)
}

func firstNonEmpty(values ...string) string {
	for _, value := range values {
		value = strings.TrimSpace(value)
		if value != "" {
			return value
		}
	}
	return ""
}

func firstPositiveInt32(values ...int32) int32 {
	for _, value := range values {
		if value > 0 {
			return value
		}
	}
	return 0
}