feat(server-go): 和风天气接入与高发病天气预警规则（#12）

server-go/internal/service/weather_risk.go

@@ -0,0 +1,68 @@
+package service
+
+import (
+	"fmt"
+	"strings"
+
+	"silk-server-go/internal/model"
+)
+
+// WeatherTextRainy 天气现象是否降雨/雷/雪
+func WeatherTextRainy(text string) bool {
+	return strings.Contains(text, "雨") || strings.Contains(text, "雷") || strings.Contains(text, "雪")
+}
+
+// RainDays 预报中降雨天数
+func RainDays(daily []DailyForecast) int {
+	n := 0
+	for _, d := range daily {
+		if WeatherTextRainy(d.TextDay) || WeatherTextRainy(d.TextNight) {
+			n++
+		}
+	}
+	return n
+}
+
+// FungalRisk 白僵病：湿度 ≥80% 且（连续阴雨 ≥2 天 或 当前降雨）
+func FungalRisk(now WeatherNow, daily []DailyForecast) (string, string) {
+	if now.Humidity >= 80 && (RainDays(daily) >= 2 || WeatherTextRainy(now.Text)) {
+		return "orange", fmt.Sprintf("实时湿度 %.0f%% 且未来 %d 天有降雨（连续阴雨），符合白僵病高发条件（湿度大于80）", now.Humidity, RainDays(daily))
+	}
+	return "", ""
+}
+
+// TempSwingRisk 核型多角体病：温度突变（>30℃ 或 <20℃）
+func TempSwingRisk(temp float64) (string, string) {
+	if temp > 30 || temp < 20 {
+		return "yellow", fmt.Sprintf("实时温度 %.0f℃ 波动剧烈（>30℃ 或 <20℃），易诱发核型多角体病潜伏感染转急性", temp)
+	}
+	return "", ""
+}
+
+// SofteningRisk 软化病：湿度 >75%（结合密度/通风可升级）
+func SofteningRisk(now WeatherNow) (string, string) {
+	if now.Humidity >= 75 {
+		return "yellow", fmt.Sprintf("实时湿度 %.0f%%（大于75），若蚕头密度过大、通风不良易发软化病", now.Humidity)
+	}
+	return "", ""
+}
+
+// EvaluateWeatherRules 综合天气规则 → 预警列表（规则取自规格书 3.2.3）
+func EvaluateWeatherRules(now WeatherNow, daily []DailyForecast, stage string) []model.WeatherAlert {
+	var alerts []model.WeatherAlert
+
+	if level, reason := FungalRisk(now, daily); level != "" {
+		alerts = append(alerts, model.WeatherAlert{Disease: "白僵病", Level: level, Reason: reason})
+	}
+	if level, reason := TempSwingRisk(now.Temp); level != "" {
+		if stage == "late5" {
+			level = "orange"
+			reason += "；当前为 5 龄后期，风险升级"
+		}
+		alerts = append(alerts, model.WeatherAlert{Disease: "核型多角体病", Level: level, Reason: reason})
+	}
+	if level, reason := SofteningRisk(now); level != "" {
+		alerts = append(alerts, model.WeatherAlert{Disease: "软化病", Level: level, Reason: reason})
+	}
+	return alerts
+}