1 files changed, 71 insertions, 0 deletions
diff --git a/lib/plugins/resolveVersion.js b/lib/plugins/resolveVersion.js
new file mode 100644
index 0000000..a24c8a0
--- /dev/null
+++ b/lib/plugins/resolveVersion.js
@@ -0,0 +1,71 @@
+var npm = require('npm');
+var semver = require('semver');
+var Immutable = require('immutable');
+
+var Promise = require('../utils/promise');
+var Plugin = require('../models/plugin');
+var gitbook = require('../gitbook');
+
+var npmIsReady;
+
+/**
+    Initialize and prepare NPM
+
+    @return {Promise}
+*/
+function initNPM() {
+    if (npmIsReady) return npmIsReady;
+
+    npmIsReady = Promise.nfcall(npm.load, {
+        silent: true,
+        loglevel: 'silent'
+    });
+
+    return npmIsReady;
+}
+
+/**
+    Resolve a plugin to a version
+
+    @param {Plugin}
+    @return {Promise<String>}
+*/
+function resolveVersion(plugin) {
+    var npmId = Plugin.nameToNpmID(plugin.getName());
+    var requiredVersion = plugin.getVersion();
+
+    if (!semver.validRange(requiredVersion)) {
+        return Promise.resolve(requiredVersion);
+    }
+
+    return initNPM()
+    .then(function() {
+        return Promise.nfcall(npm.commands.view, [npmId + '@' + requiredVersion, 'engines'], true);
+    })
+    .then(function(versions) {
+        versions = Immutable.Map(versions).entrySeq();
+
+        var result = versions
+            .map(function(entry) {
+                return {
+                    version: entry[0],
+                    gitbook: (entry[1].engines || {}).gitbook
+                };
+            })
+            .filter(function(v) {
+                return v.gitbook && gitbook.satisfies(v.gitbook);
+            })
+            .sort(function(v1, v2) {
+                return semver.lt(v1.version, v2.version)? 1 : -1;
+            })
+            .get(0);
+
+        if (!result) {
+            return undefined;
+        } else {
+            return result.version;
+        }
+    });
+}
+
+module.exports = resolveVersion;