package service

import (
	"database/sql"
	"encoding/json"
	"fmt"
	"sort"
	"strings"
	"time"

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

const (
	XLSXAvailabilityEligible          = "candidate"
	XLSXAvailabilityPDDMissing        = "pdd_missing_or_deleted"
	XLSXAvailabilityStatusUnsupported = "status_not_collected"
	XLSXAvailabilityJSONInvalid       = "pdd_json_invalid"
	XLSXAvailabilitySourceMismatch    = "spec_source_not_shopee_backfill"
	XLSXAvailabilitySKUsMissing       = "pdd_skus_missing"
	XLSXAvailabilitySpecsInvalid      = "pdd_specs_invalid"
	XLSXAvailabilityPriceInvalid      = "pdd_price_invalid"
	XLSXAvailabilityAlreadyDecided    = "availability_already_decided"
	XLSXAvailabilityMarkerInvalid     = "availability_marker_invalid"
)

// XLSXAvailabilityCandidate 是一件可安全确认导入规格可用于采购的 PDD 商品。
type XLSXAvailabilityCandidate struct {
	PDDGoodsID  string
	SKUCount    int
	Original    repository.PDDPriceBackfillTarget
	NewSKUsJSON string
}

// XLSXAvailabilityPlan 保存 dry-run 统计和事务更新需要的完整原值。
type XLSXAvailabilityPlan struct {
	Shop        string
	GeneratedAt string
	Sources     XLSXPriceSources
	Summary     map[string]int
	Candidates  []XLSXAvailabilityCandidate
}

// BuildXLSXAvailabilityPlan 仅在内存中生成三个固定 Excel 的可售确认计划。
func BuildXLSXAvailabilityPlan(sources XLSXPriceSources,
	targets []repository.PDDPriceBackfillTarget, now time.Time) XLSXAvailabilityPlan {
	plan := XLSXAvailabilityPlan{
		Shop: XLSXPriceBackfillShop, GeneratedAt: now.UTC().Format(model.TimeLayout),
		Sources: sources, Summary: make(map[string]int),
	}
	targetByID := make(map[string]repository.PDDPriceBackfillTarget, len(targets))
	for _, target := range targets {
		targetByID[target.GoodsID] = target
	}
	goodsIDs := make([]string, 0, len(sources.PDDPrices))
	for goodsID := range sources.PDDPrices {
		goodsIDs = append(goodsIDs, goodsID)
	}
	sort.Strings(goodsIDs)
	for _, goodsID := range goodsIDs {
		target, exists := targetByID[goodsID]
		if !exists {
			plan.Summary[XLSXAvailabilityPDDMissing]++
			continue
		}
		if target.CollectStatus != string(model.CollectCollected) {
			plan.Summary[XLSXAvailabilityStatusUnsupported]++
			continue
		}
		newRaw, skuCount, status := confirmBackfilledPDDAvailability(target.SKUsJSON)
		if status != XLSXAvailabilityEligible {
			plan.Summary[status]++
			continue
		}
		plan.Summary[XLSXAvailabilityEligible]++
		plan.Candidates = append(plan.Candidates, XLSXAvailabilityCandidate{
			PDDGoodsID: goodsID, SKUCount: skuCount, Original: target, NewSKUsJSON: newRaw,
		})
	}
	return plan
}

func confirmBackfilledPDDAvailability(raw string) (string, int, string) {
	var root map[string]json.RawMessage
	if err := json.Unmarshal([]byte(raw), &root); err != nil || root == nil {
		return "", 0, XLSXAvailabilityJSONInvalid
	}
	var source string
	if err := json.Unmarshal(root["spec_source"], &source); err != nil || source != "shopee_backfill" {
		return "", 0, XLSXAvailabilitySourceMismatch
	}
	var skus []map[string]json.RawMessage
	if err := json.Unmarshal(root["skus"], &skus); err != nil {
		return "", 0, XLSXAvailabilityJSONInvalid
	}
	if len(skus) == 0 {
		return "", 0, XLSXAvailabilitySKUsMissing
	}
	for _, sku := range skus {
		var options map[string]string
		if err := json.Unmarshal(sku["options"], &options); err != nil || len(options) == 0 {
			return "", 0, XLSXAvailabilitySpecsInvalid
		}
		for key, value := range options {
			if strings.TrimSpace(key) == "" || strings.TrimSpace(value) == "" {
				return "", 0, XLSXAvailabilitySpecsInvalid
			}
		}
		var price *int64
		priceRaw, hasPrice := sku["price_cent"]
		if !hasPrice || json.Unmarshal(priceRaw, &price) != nil || price == nil || *price <= 0 {
			return "", 0, XLSXAvailabilityPriceInvalid
		}
		if available, exists := sku["available"]; exists && strings.TrimSpace(string(available)) != "null" {
			return "", 0, XLSXAvailabilityAlreadyDecided
		}
		var marker string
		if err := json.Unmarshal(sku["availability_status"], &marker); err != nil || marker != "unknown" {
			return "", 0, XLSXAvailabilityMarkerInvalid
		}
	}
	for _, sku := range skus {
		sku["available"] = json.RawMessage("true")
		delete(sku, "availability_status")
	}
	encodedSKUs, err := json.Marshal(skus)
	if err != nil {
		return "", 0, XLSXAvailabilityJSONInvalid
	}
	root["skus"] = encodedSKUs
	encodedRoot, err := json.Marshal(root)
	if err != nil {
		return "", 0, XLSXAvailabilityJSONInvalid
	}
	return string(encodedRoot), len(skus), XLSXAvailabilityEligible
}

// ApplyXLSXAvailabilityPlan 在一个事务中确认全部候选；任一原值变化则整批回滚。
func ApplyXLSXAvailabilityPlan(db *sql.DB, plan XLSXAvailabilityPlan, now time.Time) (int, error) {
	tx, err := db.Begin()
	if err != nil {
		return 0, fmt.Errorf("开始确认 PDD 可售状态事务失败: %w", err)
	}
	defer tx.Rollback()
	updatedAt := now.UTC().Format(model.TimeLayout)
	updated := 0
	for _, candidate := range plan.Candidates {
		ok, err := repository.ReplaceBackfilledPDDAvailability(
			tx, candidate.Original, candidate.NewSKUsJSON, updatedAt)
		if err != nil {
			return 0, err
		}
		if !ok {
			return 0, fmt.Errorf("PDD 商品 %s 在 dry-run 后发生变化，已回滚整批可售确认", candidate.PDDGoodsID)
		}
		updated++
	}
	if err := tx.Commit(); err != nil {
		return 0, fmt.Errorf("提交 PDD 可售状态确认失败: %w", err)
	}
	return updated, nil
}