init commit for iPAL-kit plugin

src/modules/seo/autoFillMeta.ts

@@ -0,0 +1,58 @@
+import type { CollectionBeforeChangeHook } from 'payload'
+
+/**
+ * Maps document fields to SEO meta fields for auto-fill.
+ * Defaults match the Payload website template (title → meta.title).
+ */
+export type AutoFillMapping = {
+  /** Document field used to fill meta.description when empty. */
+  description?: string
+  /** Document field used to fill meta.title when empty. Default: 'title'. */
+  title?: string
+}
+
+/**
+ * Reads a possibly-localized field value into a plain string.
+ * With localized fields at this hook stage the value is the active-locale
+ * string, so we just coerce defensively.
+ */
+function readString(value: unknown): string | undefined {
+  if (typeof value === 'string' && value.trim()) {return value.trim()}
+  return undefined
+}
+
+/**
+ * Builds a beforeChange hook that fills empty SEO meta fields from document
+ * content. Only fills when the meta field is blank — never overwrites what an
+ * editor typed. This runs server-side on every create/update, so editors get
+ * sensible meta without clicking "auto-generate".
+ *
+ * The plugin doesn't know the client's collection shape, so the field mapping
+ * is configurable; defaults follow the website template.
+ */
+export function buildAutoFillMetaHook(mapping: AutoFillMapping = {}): CollectionBeforeChangeHook {
+  const titleField = mapping.title ?? 'title'
+  const descriptionField = mapping.description
+
+  return ({ data }) => {
+    if (!data) {return data}
+
+    // plugin-seo stores meta as a group under `meta`
+    const meta = (data.meta as Record<string, unknown> | undefined) ?? {}
+
+    // Fill meta.title from the document title when empty
+    if (!readString(meta.title)) {
+      const sourceTitle = readString(data[titleField])
+      if (sourceTitle) {meta.title = sourceTitle}
+    }
+
+    // Fill meta.description from a configured field when empty
+    if (descriptionField && !readString(meta.description)) {
+      const sourceDescription = readString(data[descriptionField])
+      if (sourceDescription) {meta.description = sourceDescription}
+    }
+
+    data.meta = meta
+    return data
+  }
+}