use router basepath in client plugin (#53)

* use router basepath in client plugin

This should fix #52 by building the fetch URI using publicPath and router.base

* Apply wished changes

* fix: fix linter issues

lib/index.js

@@ -140,17 +140,22 @@ module.exports = async function () {
         dirs: database.dirs
       }
     })
-
     let publicPath = this.options.build.publicPath // can be an url
+    let routerBasePath = this.options.router.base
+
     /* istanbul ignore if */
     if (publicPath[publicPath.length - 1] !== '/') {
       publicPath += '/'
     }
+    if (routerBasePath[routerBasePath.length - 1] === '/') {
+      routerBasePath = routerBasePath.slice(0, -1)
+    }
     this.addPlugin({
       fileName: 'content/plugin.client.js',
       src: join(__dirname, 'templates/plugin.static.js'),
       options: {
-        dbPath: publicPath + 'content/db.json'
+        // if publicPath is an URL, use public path, if not, add basepath before it
+        dbPath: isUrl(publicPath) ? `${publicPath}content/db.json` : `${routerBasePath}${publicPath}content/db.json`
       }
     })
   } else {
@@ -178,6 +183,16 @@ module.exports = async function () {
     fileName: 'content/nuxt-content.js',
     src: join(__dirname, 'templates/nuxt-content.js')
   })
+  function isUrl (string) {
+    try {
+      // quick test if the string is an URL
+      // eslint-disable-next-line no-new
+      new URL(string)
+    } catch (_) {
+      return false
+    }
+    return true
+  }
 }
 
 module.exports.Database = Database