3 files changed, 175 insertions, 0 deletions
diff --git a/errors/errors.go b/errors/errors.go
new file mode 100644
index 0000000..08d8a4c
--- /dev/null
+++ b/errors/errors.go
@@ -0,0 +1,51 @@
+/* openbills - Server for web based Libre Billing Software
+ * Copyright (C) 2023  Vidhu Kant Sharma <vidhukant@vidhukant.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package errors
+
+import (
+	"errors"
+)
+
+var (
+	// 204
+	ErrEmptyResponse       = errors.New("No Records Found")
+
+	// 400
+	ErrNoWhereCondition     = errors.New("No Where Condition")
+	ErrInvalidID            = errors.New("Invalid ID")
+	ErrEmptyContactName     = errors.New("Contact Name Cannot Be Empty")
+	ErrInvalidGSTIN         = errors.New("Invalid GSTIN")
+	ErrEmptyBrandName       = errors.New("Brand Name Cannot Be Empty")
+	ErrInvalidUnitPrice     = errors.New("Invalid Unit Price")
+	ErrInvalidGSTPercentage = errors.New("Invalid GST Percentage")
+
+	// 404
+	ErrNotFound             = errors.New("Not Found")
+	ErrBrandNotFound        = errors.New("This Brand Does Not Exist")
+
+	// 409
+	ErrNonUniqueGSTIN       = errors.New("GSTIN Must Be Unique")
+	ErrNonUniquePhone       = errors.New("Phone Number Must Be Unique")
+	ErrNonUniqueEmail       = errors.New("Email Address Must Be Unique")
+	ErrNonUniqueWebsite     = errors.New("Website Must Be Unique")
+	ErrNonUniqueBrandName   = errors.New("Brand Name Must Be Unique")
+	ErrNonUniqueBrandItem   = errors.New("Item With Same Name And Brand Already Exists")
+
+	// 500
+	ErrInternalServerError = errors.New("Internal Server Error")
+)
diff --git a/errors/middleware.go b/errors/middleware.go
new file mode 100644
index 0000000..6d2f344
--- /dev/null
+++ b/errors/middleware.go
@@ -0,0 +1,60 @@
+/* openbills - Server for web based Libre Billing Software
+ * Copyright (C) 2023  Vidhu Kant Sharma <vidhukant@vidhukant.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package errors
+
+import (
+	"github.com/gin-gonic/gin"
+	"log"
+)
+
+func writeLog(method, path string, statusCode int, err error) {
+	var prefix string
+	if (statusCode >= 400 && statusCode < 500) || (statusCode >= 200 && statusCode < 300) {
+		prefix = "\x1b[43m\x1b[30m[warn]\x1b[0m"
+	} else {
+		prefix = "\x1b[41m\x1b[30m[err]\x1b[0m"
+	}
+
+	log.Printf("%s \x1b[47m\x1b[30m%s %s\x1b[0m %d %s", prefix, method, path, statusCode, err.Error())
+}
+
+func ErrResponse() gin.HandlerFunc {
+	return func(ctx *gin.Context) {
+		ctx.Next()
+
+		if len(ctx.Errors) > 0 {
+			err := ctx.Errors[0].Err
+
+			status := ctx.Writer.Status()
+			if status == 200 {
+				status = StatusCodeFromErr(err)
+			}
+
+			ctx.JSON(status, gin.H{
+				"error": err.Error(),
+			})
+
+			writeLog(
+				ctx.Request.Method,
+				ctx.FullPath(),
+				status,
+				err,
+			)
+		}
+	}
+}
diff --git a/errors/status.go b/errors/status.go
new file mode 100644
index 0000000..eb59506
--- /dev/null
+++ b/errors/status.go
@@ -0,0 +1,64 @@
+/* openbills - Server for web based Libre Billing Software
+ * Copyright (C) 2023  Vidhu Kant Sharma <vidhukant@vidhukant.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package errors
+
+import (
+	"errors"
+	"net/http"
+)
+
+func StatusCodeFromErr(err error) int {
+	// 204
+	if errors.Is(err, ErrEmptyResponse) {
+		return http.StatusNoContent
+	}
+
+	// 400
+	if errors.Is(err, ErrNoWhereCondition) ||
+		errors.Is (err, ErrInvalidID) ||
+		errors.Is (err, ErrEmptyContactName) ||
+		errors.Is(err, ErrInvalidGSTIN) ||
+		errors.Is(err, ErrEmptyBrandName) ||
+		errors.Is(err, ErrInvalidUnitPrice) ||
+		errors.Is(err, ErrInvalidGSTPercentage) {
+		return http.StatusBadRequest
+	}
+
+	// 404
+	if errors.Is(err, ErrNotFound) ||
+		errors.Is(err, ErrBrandNotFound) {
+		return http.StatusNotFound
+	}
+
+	// 409
+	if errors.Is(err, ErrNonUniqueGSTIN) ||
+		errors.Is(err, ErrNonUniquePhone) ||
+		errors.Is(err, ErrNonUniqueEmail) ||
+		errors.Is(err, ErrNonUniqueWebsite) ||
+		errors.Is(err, ErrNonUniqueBrandName) ||
+		errors.Is(err, ErrNonUniqueBrandItem) {
+		return http.StatusConflict
+	}
+
+	// 500
+	if errors.Is(err, ErrInternalServerError) {
+		return http.StatusInternalServerError
+	}
+
+	return http.StatusInternalServerError
+}