package service

import (
	"context"
	"crypto/rand"
	"database/sql"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"time"

	"cmautobuy/admin/model"
	"cmautobuy/admin/repository"
	"cmautobuy/admin/syb"
)

// InnerCodeWriter 是安全回写所需的最小顺运宝接口。
type InnerCodeWriter interface {
	InnerCodeDetailReader
	DeleteInnerCode(context.Context, int64) error
	CreateInnerCodeDetail(context.Context, int64, string) (int64, error)
	UpdateDetailCode(context.Context, int64, int64, string) error
}

// InnerCodeApplyResult 是一次用户确认操作的统计。
type InnerCodeApplyResult struct {
	Requested     int
	Updated       int
	AlreadyFilled int
	Skipped       int
	Failed        int
	NeedsCheck    int
}

// InnerCodeApplyBatch 是一次已经落库的后台回写请求。
type InnerCodeApplyBatch struct {
	ID    string
	Count int
}

const innerCodeApplyChunkSize = 20

type innerCodeApplyOutcome struct {
	Status     model.InnerCodeStatus
	Message    string
	RemoteCode string
}

type innerCodeRemoteItem struct {
	Code     string `json:"code"`
	DetailID int64  `json:"detail_id,omitempty"`
	Source   string `json:"source,omitempty"`
	Title    string `json:"title,omitempty"`
	Status   string `json:"status"`
}

type innerCodeCheckpoint func([]innerCodeRemoteItem, string) error

// QueueInnerCodeApplyBatch 把任意数量的已选记录原子排队，远端请求由后台执行器处理。
func QueueInnerCodeApplyBatch(db *sql.DB, ids []int64, actorUserID string) (*InnerCodeApplyBatch, error) {
	ids = uniquePositiveInnerCodeIDs(ids)
	if len(ids) == 0 {
		return nil, fmt.Errorf("没有选择可回写记录")
	}
	batchID, err := newInnerCodeApplyBatchID()
	if err != nil {
		return nil, err
	}
	count, err := repository.QueueInnerCodeApplyBatch(db, ids, batchID, actorUserID, model.NowISO())
	if err != nil {
		if errors.Is(err, repository.ErrInnerCodeApplyConflict) {
			return nil, fmt.Errorf("所选记录中有记录已不再可回写；本批没有部分入队，请刷新后重新选择")
		}
		return nil, err
	}
	return &InnerCodeApplyBatch{ID: batchID, Count: count}, nil
}

// RunInnerCodeApplyBatch 分组读取后台队列，再逐条执行原有安全回写门禁。
// 分组大小只用于控制一次数据库读取，远端请求始终逐条发送且不会自动重试。
func RunInnerCodeApplyBatch(ctx context.Context, db *sql.DB, writer InnerCodeWriter, batchID, actorUserID string) (*InnerCodeApplyResult, error) {
	result := &InnerCodeApplyResult{}
	for {
		if err := ctx.Err(); err != nil {
			return result, err
		}
		ids, err := repository.ListQueuedInnerCodeIDs(db, batchID, innerCodeApplyChunkSize)
		if err != nil {
			return result, err
		}
		if len(ids) == 0 {
			return result, nil
		}
		result.Requested += len(ids)
		for _, id := range ids {
			if err := ctx.Err(); err != nil {
				return result, err
			}
			now := model.NowISO()
			record, claimed, err := repository.ClaimQueuedInnerCodeForApply(db, id, batchID, actorUserID, now)
			if err != nil {
				return result, err
			}
			if !claimed {
				result.Skipped++
				continue
			}
			checkpoint := func(items []innerCodeRemoteItem, message string) error {
				raw, err := json.Marshal(items)
				if err != nil {
					return fmt.Errorf("序列化档口入库码逐件检查点失败: %w", err)
				}
				return repository.SaveInnerCodeRemoteItems(db, id, string(raw), compactInnerCodeMessage(message), model.NowISO())
			}
			outcome := applyClaimedInnerCode(ctx, writer, *record, checkpoint)
			finishedAt := model.NowISO()
			if err := repository.FinishInnerCodeApply(db, id, outcome.Status, compactInnerCodeMessage(outcome.Message), outcome.RemoteCode, finishedAt); err != nil {
				return result, err
			}
			switch outcome.Status {
			case model.InnerCodeUpdated:
				result.Updated++
			case model.InnerCodeAlreadyFilled:
				result.AlreadyFilled++
			case model.InnerCodeNeedsCheck:
				result.NeedsCheck++
			case model.InnerCodeFailed:
				result.Failed++
			default:
				result.Skipped++
			}
		}
	}
}

// InterruptInnerCodeApplyBatch 在后台异常时收敛当前批次，不自动重试任何远端请求。
func InterruptInnerCodeApplyBatch(db *sql.DB, batchID string) (int, int, error) {
	return repository.InterruptInnerCodeApplyBatch(db, strings.TrimSpace(batchID), model.NowISO())
}

// GetInnerCodeApplyBatchProgress 返回页面使用的单表聚合进度。
func GetInnerCodeApplyBatchProgress(db *sql.DB, batchID string) (*repository.InnerCodeApplyBatchProgress, error) {
	batchID = strings.TrimSpace(batchID)
	if batchID == "" || len(batchID) > 191 {
		return nil, nil
	}
	return repository.GetInnerCodeApplyBatchProgress(db, batchID)
}

func newInnerCodeApplyBatchID() (string, error) {
	random := make([]byte, 8)
	if _, err := rand.Read(random); err != nil {
		return "", fmt.Errorf("生成档口入库码后台批次失败: %w", err)
	}
	return "ICB-" + time.Now().UTC().Format("20060102T150405") + "-" + hex.EncodeToString(random), nil
}

func applyClaimedInnerCode(ctx context.Context, writer InnerCodeWriter, record model.InnerCodeRecord, checkpoint innerCodeCheckpoint) innerCodeApplyOutcome {
	codes, err := splitInnerCodes(record.InnerCode)
	if err != nil || len(codes) != record.SourceDuplicateCount {
		return innerCodeApplyOutcome{Status: model.InnerCodeFailed,
			Message: fmt.Sprintf("导入单件码数量与源行数不一致（入库码 %d 个，源行 %d 行），没有发送远端写请求", len(codes), record.SourceDuplicateCount), RemoteCode: record.RemoteInnerCode}
	}
	stock, original, err := readCurrentInnerCodeStock(ctx, writer, record)
	if err != nil {
		return innerCodeApplyOutcome{Status: model.InnerCodeNeedsCheck,
			Message: "写入前重新读取失败，没有发送远端写请求：" + err.Error(), RemoteCode: record.RemoteInnerCode}
	}
	if original.ProductQty != len(codes) {
		return innerCodeApplyOutcome{Status: model.InnerCodeFailed,
			Message: fmt.Sprintf("顺运宝商品数量为 %d，单件入库码为 %d 个，数量不一致；没有发送远端写请求", original.ProductQty, len(codes)), RemoteCode: innerCodeRawText(original.Raw["innerExpCode"])}
	}
	if !innerCodeDetailIdentityMatches(record, *original) {
		return innerCodeApplyOutcome{Status: model.InnerCodeSkipped,
			Message: "顺运宝商品规格或档口身份已变化，停止回写，请重新匹配", RemoteCode: innerCodeRawText(original.Raw["innerExpCode"])}
	}
	if innerCodeRawText(original.Raw["purchasePlatform"]) != "" || innerCodeRawText(original.Raw["purchaseCode"]) != "" {
		return innerCodeApplyOutcome{Status: model.InnerCodeSkipped,
			Message: "顺运宝商品已有采购平台或采购单号，停止回写", RemoteCode: innerCodeRawText(original.Raw["innerExpCode"])}
	}
	items, missing, prepareErr := planInnerCodeRemoteItems(record, stock, codes)
	if prepareErr != nil {
		return innerCodeApplyOutcome{Status: model.InnerCodeNeedsCheck, Message: prepareErr.Error(), RemoteCode: record.RemoteInnerCode}
	}
	if checkpoint == nil {
		checkpoint = func([]innerCodeRemoteItem, string) error { return nil }
	}
	if len(missing) == 0 {
		if err := checkpoint(items, fmt.Sprintf("远端已存在全部 %d 个单件入库码", len(codes))); err != nil {
			return innerCodeApplyOutcome{Status: model.InnerCodeNeedsCheck, Message: err.Error(), RemoteCode: strings.Join(codes, ",")}
		}
		return innerCodeApplyOutcome{Status: model.InnerCodeAlreadyFilled,
			Message: fmt.Sprintf("远端已存在全部 %d 个单件入库码，无需重复写入", len(codes)), RemoteCode: strings.Join(codes, ",")}
	}

	currentCode := innerCodeRawText(original.Raw["innerExpCode"])
	if currentCode != "" && !containsInnerCode(codes, currentCode) {
		if currentCode != record.RemoteInnerCode {
			return innerCodeApplyOutcome{Status: model.InnerCodeNeedsCheck,
				Message: "原商品快递单号在规划后发生变化，已停止回写，请人工核对", RemoteCode: currentCode}
		}
		if err := checkpoint(items, "准备清除原商品上的旧快递单号"); err != nil {
			return innerCodeApplyOutcome{Status: model.InnerCodeNeedsCheck, Message: err.Error(), RemoteCode: currentCode}
		}
		if err := writer.DeleteInnerCode(ctx, record.DetailID); err != nil {
			return withInnerCodeProgress(unknownOrFailedInnerCodeOutcome(err, "删除旧快递单号", currentCode), items)
		}
		currentCode = ""
	}

	for _, codeIndex := range missing {
		item := &items[codeIndex]
		if item.DetailID == 0 && currentCode == "" {
			item.DetailID = record.DetailID
			item.Source = "original"
			currentCode = "reserved"
		}
		if item.DetailID == 0 {
			item.Title = innerCodePlaceholderTitle(record.ID, codeIndex+1)
			item.Status = "creating"
			if err := checkpoint(items, fmt.Sprintf("准备为第 %d 件创建零价明细", codeIndex+1)); err != nil {
				return innerCodeApplyOutcome{Status: model.InnerCodeNeedsCheck, Message: err.Error(), RemoteCode: record.RemoteInnerCode}
			}
			detailID, err := writer.CreateInnerCodeDetail(ctx, record.StockID, item.Title)
			if err != nil {
				return withInnerCodeProgress(unknownOrFailedInnerCodeOutcome(err, fmt.Sprintf("创建第 %d 件明细", codeIndex+1), record.RemoteInnerCode), items)
			}
			item.DetailID = detailID
			item.Source = "created"
			item.Status = "created"
			if err := checkpoint(items, fmt.Sprintf("第 %d 件明细已创建，准备写入入库码", codeIndex+1)); err != nil {
				return innerCodeApplyOutcome{Status: model.InnerCodeNeedsCheck, Message: "新增明细后保存检查点失败，禁止继续写入：" + err.Error(), RemoteCode: record.RemoteInnerCode}
			}
		}
		item.Status = "writing"
		if err := checkpoint(items, fmt.Sprintf("准备写入第 %d 个单件入库码", codeIndex+1)); err != nil {
			return innerCodeApplyOutcome{Status: model.InnerCodeNeedsCheck, Message: err.Error(), RemoteCode: record.RemoteInnerCode}
		}
		if err := writer.UpdateDetailCode(ctx, record.StockID, item.DetailID, item.Code); err != nil {
			return withInnerCodeProgress(unknownOrFailedInnerCodeOutcome(err, fmt.Sprintf("写入第 %d 个单件入库码", codeIndex+1), record.RemoteInnerCode), items)
		}
		verifiedStock, _, err := readCurrentInnerCodeStock(ctx, writer, record)
		if err != nil {
			return innerCodeApplyOutcome{Status: model.InnerCodeNeedsCheck, Message: "写入成功响应后重新读取失败，禁止自动重试", RemoteCode: record.RemoteInnerCode}
		}
		if countInnerCodeInStock(verifiedStock, item.Code) != 1 || innerCodeDetailCode(verifiedStock, item.DetailID) != item.Code {
			return innerCodeApplyOutcome{Status: model.InnerCodeNeedsCheck, Message: "写入后单件入库码未唯一出现在预期明细，禁止自动重试", RemoteCode: record.RemoteInnerCode}
		}
		item.Status = "confirmed"
		if err := checkpoint(items, fmt.Sprintf("第 %d 个单件入库码已回读确认", codeIndex+1)); err != nil {
			return innerCodeApplyOutcome{Status: model.InnerCodeNeedsCheck, Message: "写入确认后保存检查点失败，请人工核对：" + err.Error(), RemoteCode: record.RemoteInnerCode}
		}
	}
	return innerCodeApplyOutcome{Status: model.InnerCodeUpdated,
		Message: fmt.Sprintf("回写完成：%d 个单件入库码均已逐件回读确认", len(codes)), RemoteCode: strings.Join(codes, ",")}
}

func readCurrentInnerCodeDetail(ctx context.Context, reader InnerCodeDetailReader, record model.InnerCodeRecord) (*syb.DetailItem, error) {
	_, found, err := readCurrentInnerCodeStock(ctx, reader, record)
	return found, err
}

func readCurrentInnerCodeStock(ctx context.Context, reader InnerCodeDetailReader, record model.InnerCodeRecord) (syb.StockDetail, *syb.DetailItem, error) {
	if record.StockID <= 0 || record.DetailID <= 0 {
		return syb.StockDetail{}, nil, fmt.Errorf("记录缺少有效的货运单或商品明细 ID")
	}
	stocks, err := reader.DetailListByStock(ctx, []int64{record.StockID})
	if err != nil {
		return syb.StockDetail{}, nil, err
	}
	if len(stocks) != 1 || stocks[0].ID != record.StockID {
		return syb.StockDetail{}, nil, fmt.Errorf("顺运宝没有唯一返回货运单 id=%d", record.StockID)
	}
	var found *syb.DetailItem
	for index := range stocks[0].Details {
		if stocks[0].Details[index].ID != record.DetailID {
			continue
		}
		if found != nil {
			return syb.StockDetail{}, nil, fmt.Errorf("顺运宝重复返回商品明细 id=%d", record.DetailID)
		}
		item := stocks[0].Details[index]
		found = &item
	}
	if found == nil {
		return syb.StockDetail{}, nil, fmt.Errorf("顺运宝未返回商品明细 id=%d", record.DetailID)
	}
	return stocks[0], found, nil
}

func splitInnerCodes(raw string) ([]string, error) {
	parts := strings.Split(raw, ",")
	codes := make([]string, 0, len(parts))
	seen := make(map[string]bool, len(parts))
	for _, part := range parts {
		code := strings.TrimSpace(part)
		if code == "" {
			return nil, fmt.Errorf("单件入库码不能为空")
		}
		if seen[code] {
			return nil, fmt.Errorf("单件入库码 %q 重复", code)
		}
		seen[code] = true
		codes = append(codes, code)
	}
	return codes, nil
}

func planInnerCodeRemoteItems(record model.InnerCodeRecord, stock syb.StockDetail, codes []string) ([]innerCodeRemoteItem, []int, error) {
	items := make([]innerCodeRemoteItem, len(codes))
	indexByCode := make(map[string]int, len(codes))
	for index, code := range codes {
		items[index] = innerCodeRemoteItem{Code: code, Status: "planned"}
		indexByCode[code] = index
	}
	for _, detail := range stock.Details {
		code := innerCodeRawText(detail.Raw["innerExpCode"])
		if index, ok := indexByCode[code]; ok {
			if items[index].DetailID != 0 {
				return nil, nil, fmt.Errorf("单件入库码 %s 在货运单中出现多次，停止自动回写", code)
			}
			source := "existing"
			if detail.ID == record.DetailID {
				source = "original"
			}
			items[index].DetailID = detail.ID
			items[index].Source = source
			items[index].Status = "confirmed"
			continue
		}
		for index := range items {
			title := innerCodePlaceholderTitle(record.ID, index+1)
			if detail.ProductTitle != title {
				continue
			}
			if items[index].DetailID != 0 {
				return nil, nil, fmt.Errorf("第 %d 件占位明细在货运单中出现多次，停止自动回写", index+1)
			}
			if code != "" {
				return nil, nil, fmt.Errorf("第 %d 件占位明细已有非目标快递单号，停止自动回写", index+1)
			}
			items[index].DetailID = detail.ID
			items[index].Source = "existing_placeholder"
			items[index].Title = title
			items[index].Status = "created"
		}
	}
	missing := make([]int, 0, len(items))
	for index := range items {
		if items[index].Status != "confirmed" {
			missing = append(missing, index)
		}
	}
	return items, missing, nil
}

func innerCodePlaceholderTitle(recordID int64, ordinal int) string {
	return fmt.Sprintf("档口第%d件-IC%d", ordinal, recordID)
}

func containsInnerCode(codes []string, value string) bool {
	for _, code := range codes {
		if code == value {
			return true
		}
	}
	return false
}

func countInnerCodeInStock(stock syb.StockDetail, code string) int {
	count := 0
	for _, detail := range stock.Details {
		if innerCodeRawText(detail.Raw["innerExpCode"]) == code {
			count++
		}
	}
	return count
}

func innerCodeDetailCode(stock syb.StockDetail, detailID int64) string {
	for _, detail := range stock.Details {
		if detail.ID == detailID {
			return innerCodeRawText(detail.Raw["innerExpCode"])
		}
	}
	return ""
}

func unknownOrFailedInnerCodeOutcome(err error, action, remoteCode string) innerCodeApplyOutcome {
	status := model.InnerCodeFailed
	message := action + "失败，系统不会自动重试：" + err.Error()
	if errors.Is(err, syb.ErrWriteResultUnknown) {
		status = model.InnerCodeNeedsCheck
		message = action + "结果未知，禁止自动重试，请重新核对"
	}
	return innerCodeApplyOutcome{Status: status, Message: message, RemoteCode: remoteCode}
}

func withInnerCodeProgress(outcome innerCodeApplyOutcome, items []innerCodeRemoteItem) innerCodeApplyOutcome {
	confirmed := 0
	for _, item := range items {
		if item.Status == "confirmed" {
			confirmed++
		}
	}
	outcome.Message = fmt.Sprintf("已确认 %d/%d 件；%s", confirmed, len(items), outcome.Message)
	return outcome
}

// RecheckInnerCode 只重新读取一条 needs_check 记录，不发送任何写请求。
func RecheckInnerCode(ctx context.Context, db *sql.DB, reader InnerCodeDetailReader, id int64) (model.InnerCodeStatus, string, error) {
	record, err := repository.GetInnerCodeForRecheck(db, id)
	if err != nil {
		return "", "", err
	}
	if record == nil {
		return "", "", fmt.Errorf("档口入库码记录不存在")
	}
	if record.Status != model.InnerCodeNeedsCheck {
		return record.Status, "当前记录不需要核对", nil
	}
	stock, item, readErr := readCurrentInnerCodeStock(ctx, reader, *record)
	status := model.InnerCodeNeedsCheck
	remoteCode := record.RemoteInnerCode
	remoteItemsJSON := record.RemoteItemsJSON
	message := "重新读取失败，仍需人工核对：" + errorText(readErr)
	if readErr == nil {
		codes, splitErr := splitInnerCodes(record.InnerCode)
		items, missing, planErr := planInnerCodeRemoteItems(*record, stock, codes)
		if splitErr == nil && planErr == nil {
			if raw, err := json.Marshal(items); err == nil {
				remoteItemsJSON = string(raw)
			}
		}
		remoteCode = innerCodeRawText(item.Raw["innerExpCode"])
		if !innerCodeDetailIdentityMatches(*record, *item) {
			message = "重新读取到的商品身份与规划不一致；保持需核对，系统没有写入"
		} else if splitErr != nil || planErr != nil {
			message = "重新读取到的逐件入库码存在冲突；保持需核对，系统没有写入"
		} else if len(missing) == 0 {
			status = model.InnerCodeUpdated
			remoteCode = strings.Join(codes, ",")
			message = fmt.Sprintf("重新读取确认远端已存在全部 %d 个单件入库码；没有重复写入", len(codes))
		} else {
			message = fmt.Sprintf("重新读取后仍缺少 %d 个单件入库码；保持需核对，系统没有写入", len(missing))
		}
	}
	checkedAt := model.NowISO()
	message = compactInnerCodeMessage(message)
	if err := repository.SaveInnerCodeRecheck(db, id, status, message, remoteCode, remoteItemsJSON, checkedAt); err != nil {
		return "", "", err
	}
	return status, message, nil
}

func innerCodeDetailIdentityMatches(record model.InnerCodeRecord, item syb.DetailItem) bool {
	return item.ProductSpec == record.SybSpec &&
		innerCodeRawText(item.Raw["sku"]) == record.SybSKU &&
		innerCodeRawText(item.Raw["variationSku"]) == record.SybVariationSKU
}

func errorText(err error) string {
	if err == nil {
		return ""
	}
	return err.Error()
}

func uniquePositiveInnerCodeIDs(ids []int64) []int64 {
	seen := make(map[int64]bool, len(ids))
	result := make([]int64, 0, len(ids))
	for _, id := range ids {
		if id > 0 && !seen[id] {
			seen[id] = true
			result = append(result, id)
		}
	}
	return result
}

// InterruptApplyingInnerCodes 在 Admin 启动时收敛未确认的远端写结果。
func InterruptApplyingInnerCodes(db *sql.DB, now time.Time) (int, error) {
	return repository.InterruptApplyingInnerCodes(db, now.UTC().Format(model.TimeLayout))
}

func compactInnerCodeMessage(message string) string {
	message = strings.TrimSpace(message)
	if len([]rune(message)) <= 500 {
		return message
	}
	return string([]rune(message)[:500])
}