feat: initial blog engine with multi-language, profile, and role system

- Gin + GORM + Tailwind CSS blog engine
- OS-aware config (Linux /etc/blog_go/, Windows ./win/etc/blog_go/)
- SQLite by default, MySQL support via config
- Auto-migrate database + seed admin user on first run
- Session-based auth (login/logout)
- i18n: Chinese/English with auto-detect + manual switch
- Avatar dropdown nav with click-to-toggle menu
- Profile page: avatar upload, edit info, change password
- Role system: admin (full access) and author (profile only)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

handlers/admin.go

@@ -0,0 +1,19 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+)
+
+// AdminDashboard renders the protected admin dashboard.
+func AdminDashboard() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		tr := getTr(c)
+		username, _ := c.Get("username")
+		data := DefaultData(c)
+		data["Title"] = tr["dash_page_title"]
+		data["Username"] = username
+		c.HTML(http.StatusOK, "dashboard", data)
+	}
+}

handlers/auth.go

@@ -0,0 +1,64 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/gin-contrib/sessions"
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+
+	"go_blog/models"
+)
+
+// LoginPage renders the login form.
+func LoginPage() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		tr := getTr(c)
+		data := DefaultData(c)
+		data["Title"] = tr["page_login"]
+		if c.Query("error") == "1" {
+			data["Error"] = tr["login_error"]
+		}
+		c.HTML(http.StatusOK, "login", data)
+	}
+}
+
+// Login processes the login form submission.
+func Login(db *gorm.DB) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		username := c.PostForm("username")
+		password := c.PostForm("password")
+
+		var user models.User
+		if err := db.Where("username = ?", username).First(&user).Error; err != nil {
+			c.Redirect(http.StatusFound, "/login?error=1")
+			return
+		}
+
+		if !user.CheckPassword(password) {
+			c.Redirect(http.StatusFound, "/login?error=1")
+			return
+		}
+
+		// Create session.
+		session := sessions.Default(c)
+		session.Set("user_id", user.ID)
+		session.Set("username", user.Username)
+		if err := session.Save(); err != nil {
+			c.String(http.StatusInternalServerError, "Failed to save session")
+			return
+		}
+
+		c.Redirect(http.StatusFound, "/admin")
+	}
+}
+
+// Logout clears the session and redirects home.
+func Logout() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		session := sessions.Default(c)
+		session.Clear()
+		session.Save()
+		c.Redirect(http.StatusFound, "/")
+	}
+}

handlers/helpers.go

@@ -0,0 +1,44 @@
+package handlers
+
+import (
+	"github.com/gin-gonic/gin"
+)
+
+// DefaultData builds a base gin.H map populated with values set by the
+// SetUserContext middleware (translations, language, auth state). Handlers
+// add page-specific fields on top and pass it to c.HTML().
+func DefaultData(c *gin.Context) gin.H {
+	tr, _ := c.Get("tr")
+	isLoggedIn, _ := c.Get("is_logged_in")
+	username, _ := c.Get("username")
+	lang, _ := c.Get("lang")
+	switchLang, _ := c.Get("switch_lang")
+	avatar, _ := c.Get("avatar")
+	displayName, _ := c.Get("display_name")
+	role, _ := c.Get("role")
+
+	return gin.H{
+		"Tr":          tr,
+		"IsLoggedIn":  isLoggedIn,
+		"Username":    username,
+		"Lang":        lang,
+		"SwitchLang":  switchLang,
+		"Avatar":      avatar,
+		"DisplayName": displayName,
+		"Role":        role,
+	}
+}
+
+// getTr is a convenience helper that returns the translation map from the
+// Gin context, falling back to an empty map if not set.
+func getTr(c *gin.Context) map[string]string {
+	tr, ok := c.Get("tr")
+	if !ok {
+		return map[string]string{}
+	}
+	m, ok := tr.(map[string]string)
+	if !ok {
+		return map[string]string{}
+	}
+	return m
+}

handlers/home.go

@@ -0,0 +1,17 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+)
+
+// HomePage renders the public home page.
+func HomePage() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		tr := getTr(c)
+		data := DefaultData(c)
+		data["Title"] = tr["page_home"]
+		c.HTML(http.StatusOK, "home", data)
+	}
+}

handlers/profile.go

@@ -0,0 +1,144 @@
+package handlers
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/gin-contrib/sessions"
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+
+	"go_blog/models"
+)
+
+// ProfilePage renders the profile edit page.
+func ProfilePage(db *gorm.DB) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		tr := getTr(c)
+		session := sessions.Default(c)
+		userID := session.Get("user_id")
+
+		var user models.User
+		if err := db.First(&user, userID).Error; err != nil {
+			c.String(http.StatusInternalServerError, "User not found")
+			return
+		}
+
+		data := DefaultData(c)
+		data["Title"] = tr["profile_title"]
+		data["Profile"] = user
+
+		// Flash messages (success / error).
+		if msg := c.Query("saved"); msg == "1" {
+			data["Success"] = tr["profile_saved"]
+		}
+		if msg := c.Query("error"); msg == "pw" {
+			data["Error"] = tr["profile_wrong_password"]
+		}
+
+		c.HTML(http.StatusOK, "profile", data)
+	}
+}
+
+// UpdateProfile processes the profile edit form (multipart).
+func UpdateProfile(db *gorm.DB, storagePath string) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		session := sessions.Default(c)
+		userID := session.Get("user_id")
+
+		var user models.User
+		if err := db.First(&user, userID).Error; err != nil {
+			c.Redirect(http.StatusFound, "/profile")
+			return
+		}
+
+		// --- Text fields ---
+		if v := c.PostForm("display_name"); v != "" {
+			user.DisplayName = v
+		}
+		if v := c.PostForm("gender"); v != "" {
+			user.Gender = v
+		}
+		if v := c.PostForm("email"); v != "" {
+			user.Email = v
+		}
+		if v := c.PostForm("birthday"); v != "" {
+			if t, err := time.Parse("2006-01-02", v); err == nil {
+				user.Birthday = &t
+			}
+		}
+
+		// --- Avatar upload ---
+		file, header, err := c.Request.FormFile("avatar")
+		if err == nil {
+			defer file.Close()
+
+			// Determine file extension.
+			ext := strings.ToLower(filepath.Ext(header.Filename))
+			if ext == "" || (ext != ".jpg" && ext != ".jpeg" && ext != ".png" && ext != ".gif" && ext != ".webp") {
+				ext = ".jpg"
+			}
+
+			// Save under storagePath/avatars/.
+			avatarDir := filepath.Join(storagePath, "avatars")
+			if err := os.MkdirAll(avatarDir, 0755); err != nil {
+				c.Redirect(http.StatusFound, "/profile")
+				return
+			}
+
+			// Use user ID as filename base to avoid duplicates.
+			savedName := fmt.Sprintf("%d%s", user.ID, ext)
+			savedPath := filepath.Join(avatarDir, savedName)
+
+			dst, err := os.Create(savedPath)
+			if err != nil {
+				c.Redirect(http.StatusFound, "/profile")
+				return
+			}
+			defer dst.Close()
+
+			if _, err := io.Copy(dst, file); err != nil {
+				c.Redirect(http.StatusFound, "/profile")
+				return
+			}
+
+			user.Avatar = savedName
+			// Update session display immediately.
+			session.Set("avatar", savedName)
+		}
+
+		// --- Password change ---
+		currentPass := c.PostForm("current_password")
+		newPass := c.PostForm("new_password")
+		if currentPass != "" && newPass != "" {
+			if !user.CheckPassword(currentPass) {
+				session.Save()
+				c.Redirect(http.StatusFound, "/profile?error=pw")
+				return
+			}
+			if err := user.SetPassword(newPass); err != nil {
+				session.Save()
+				c.Redirect(http.StatusFound, "/profile")
+				return
+			}
+		}
+
+		// Save user record.
+		if err := db.Save(&user).Error; err != nil {
+			session.Save()
+			c.Redirect(http.StatusFound, "/profile")
+			return
+		}
+
+		// Update display name in session.
+		session.Set("display_name", user.DisplayName)
+		session.Save()
+
+		c.Redirect(http.StatusFound, "/profile?saved=1")
+	}
+}