From 3c81a179ccafe68ad04c3bb3d0a2c454da798fd7 Mon Sep 17 00:00:00 2001
From: Helmut Merz <helmutm@cy55.de>
Date: Thu, 24 Aug 2023 09:32:11 +0200
Subject: [PATCH] experimental: build query functionality using templates

---
 storage/msgstore/msgstore.go | 25 +++++++++++++++++++------
 storage/sql/sql.go           | 16 ++++++++++------
 2 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/storage/msgstore/msgstore.go b/storage/msgstore/msgstore.go
index 91a09e6..829dbae 100644
--- a/storage/msgstore/msgstore.go
+++ b/storage/msgstore/msgstore.go
@@ -1,16 +1,29 @@
 package msgstore
 
 import (
+	"text/template"
+
 	lib "git.sr.ht/~cco/go-scopes"
 	"git.sr.ht/~cco/go-scopes/storage/sql"
 )
 
-func Store(db *sql.Storage, msg lib.Message) {
-	q := db.SetTable(sql_insert_msg, "messages")
+var Store = func(db *sql.Storage, msg lib.Message) {
+	q := buildQuery(db, "insert_msg", "messages")
 	db.Exec(q, msg.Domain(), msg.Action(), msg.Class(), msg.Item(), msg.Payload())
 }
 
-const (
-	sql_insert_msg = `insert into {{ .table }} (domain, action, class, item, payload)
-		values ($1, $2, $3, $4, $5)`
-)
+func buildQuery(db *sql.Storage, qname, tname string) string {
+	t, ok := sql_templates[qname]
+	if !ok {
+		t = db.ParseTemplate(sql_sources[qname])
+		sql_templates[qname] = t
+	}
+	return db.SetTable(t, tname)
+}
+
+var sql_templates = map[string]*template.Template{}
+
+var sql_sources = map[string]string{
+	"insert_msg": `insert into {{ .table }} (domain, action, class, item, payload)
+		values ($1, $2, $3, $4, $5)`,
+}
diff --git a/storage/sql/sql.go b/storage/sql/sql.go
index c36c428..b4a1ce3 100644
--- a/storage/sql/sql.go
+++ b/storage/sql/sql.go
@@ -119,21 +119,25 @@ func (db *Storage) RunScript(path string) error {
 	return err
 }
 
-func (db *Storage) SetTable(q, tname string) string {
+func (db *Storage) ParseTemplate(q string) *template.Template {
 	t, err := template.New("sql").Parse(q)
 	if err != nil {
-		db.logErr(err, "sql.Storage.SetTable", q)
-		return q
+		db.logErr(err, "sql.Storage.ParseTemplate", q)
+		return nil
 	}
+	return t
+}
+
+func (db *Storage) SetTable(t *template.Template, tname string) string {
 	if db.Cfg.Schema != "" {
 		tname = db.Cfg.Schema + "." + tname
 	}
 	var out strings.Builder
 	data := map[string]interface{}{"table": tname}
-	err = t.Execute(&out, data)
+	err := t.Execute(&out, data)
 	if err != nil {
-		db.logErr(err, "sql.Storage.SetTable", q)
-		return q
+		db.logErr(err, "sql.Storage.SetTable", fmt.Sprintf("%+v", t))
+		return ""
 	}
 	return out.String()
 }