package rain

import (
	"context"
	"fmt"
	"log"
	"os"
	"path"
	"regexp"
	"strconv"
	"strings"
	"time"
	"weatherstation/internal/database"
)

var (
	// Matches .../<PRODUCT>/<YYYYMMDD>/<HH>/<mm>/<z>/<y>/<x>.bin
	// Example: /tiles/China/CMPA_RT_China_0P01_HOR-PRE_GISJPG_Tiles/20251007/01/00/7/40/102.bin
	tileRE = regexp.MustCompile(`(?i)/tiles/.+?/([^/]+)/([0-9]{8})/([0-9]{2})/([0-9]{2})/([0-9]+)/([0-9]+)/([0-9]+)\.bin$`)
)

// TileRef references a CMPA rain tile.
type TileRef struct {
	Product string
	DT      time.Time // nominal time in Asia/Shanghai (UTC+8)
	Z, Y, X int
}

// ParseCMPATileURL parses a CMPA tile URL/path and extracts product, time (UTC+8), z/y/x.
// The timestamp in the path is UTC; we convert to Asia/Shanghai by adding 8h.
func ParseCMPATileURL(u string) (TileRef, error) {
	p := u
	if i := strings.IndexAny(p, "?#"); i >= 0 {
		p = p[:i]
	}
	p = path.Clean(p)
	m := tileRE.FindStringSubmatch(p)
	if len(m) == 0 {
		return TileRef{}, fmt.Errorf("unrecognized CMPA tile path: %s", u)
	}
	product := m[1]
	yyyymmdd := m[2]
	hh := m[3]
	mm := m[4]
	z := mustAtoi(m[5])
	y := mustAtoi(m[6])
	x := mustAtoi(m[7])

	// Parse as UTC then shift to CST(+8)
	utcT, err := time.ParseInLocation("20060102 15 04", fmt.Sprintf("%s %s %s", yyyymmdd, hh, mm), time.UTC)
	if err != nil {
		return TileRef{}, fmt.Errorf("parse utc time: %w", err)
	}
	loc, _ := time.LoadLocation("Asia/Shanghai")
	if loc == nil {
		loc = time.FixedZone("CST", 8*3600)
	}
	dt := utcT.In(loc)
	return TileRef{Product: product, DT: dt, Z: z, Y: y, X: x}, nil
}

func mustAtoi(s string) int { n, _ := strconv.Atoi(s); return n }

// StoreTileBytes parses the URL, computes metadata and upserts into rain_tiles.
func StoreTileBytes(ctx context.Context, urlOrPath string, data []byte) error {
	ref, err := ParseCMPATileURL(urlOrPath)
	if err != nil {
		return err
	}
	// 可选：强制 +8 小时（若上游传入的时间已为 UTC 且未转换，可用此开关修正）
	if strings.EqualFold(strings.TrimSpace(strings.ToLower(os.Getenv("RAIN_FORCE_SHIFT8"))), "1") {
		ref.DT = ref.DT.Add(8 * time.Hour)
	}
	// 可选调试：打印解析出的时间（CST）与 URL
	if strings.EqualFold(strings.TrimSpace(strings.ToLower(os.Getenv("RAIN_DEBUG"))), "1") {
		log.Printf("[rain] store tile: url=%s -> product=%s dt(local)=%s z=%d y=%d x=%d",
			urlOrPath, ref.Product, ref.DT.Format("2006-01-02 15:04:05 -0700"), ref.Z, ref.Y, ref.X)
	}
	db := database.GetDB()
	return database.UpsertRainTile(ctx, db, ref.Product, ref.DT, ref.Z, ref.Y, ref.X, 256, 256, data)
}