Work on native gui: views and database model

yms/model/dbrecord.py

@@ -0,0 +1,137 @@
+# SPDX-License-Identifier: WTFPL
+
+"""
+No commits here: Has to be done elsewhere to support transactions!
+
+"""
+
+from datetime import datetime
+
+class DbRecord:
+
+    def __init__(self, db, record_id=None):
+        if not hasattr(self, "table"):
+            raise TypeError("DbRecord subclass must define 'table'")
+        if not hasattr(self, "pk_field"):
+            raise TypeError("DbRecord subclass must define 'pk_field'")
+        if not hasattr(self, "fields"):
+            raise TypeError("DbRecord subclass must define 'fields'")
+
+        self.db = db
+        self.dcur = db.dcur
+        self.conn = db.conn
+        self.last_update = None
+
+        self.title = _("DbRecord({})") # for pretty print
+
+        if record_id is not None:
+            self.pk_value = int(record_id)
+            self.load()
+        else:
+            self.pk_value = None
+            self.clear()
+
+    def clear(self):
+        for field in self.fields:
+            setattr(self, field, None)
+        self.data = {} # for old/new checks
+
+    def load(self, record_id=None):
+        if record_id is not None:
+            self.pk_value = int(record_id)
+        if self.pk_value is None:
+            self.clear()
+            return
+        sql = ("SELECT {} FROM {} WHERE {}=%s").format(', '.join(self.fields), self.table, self.pk_field)
+        try:
+            self.dcur.execute(sql, (self.pk_value,))
+            self.data = self.dcur.fetchone()
+        except Exception as e:
+            self.db.error = e
+            self.clear()
+            return False
+        if self.data:
+            for field, value in self.data.items():
+                setattr(self, field, value)
+            return True
+        else:
+            self.clear()
+            return False
+
+    def save(self):
+        self.last_update = datetime.now()
+        if self.pk_value is not None:
+            return self._update()
+        else:
+            return self._insert()
+
+    def _update(self):
+        sqlfield = []
+        values = []
+        for field in self.fields:
+            newdata = getattr(self, field)
+            if self.data[field] != newdata:
+                sqlfield.append("{}=%s".format(field))
+                values.append(newdata)
+        if values:
+            # only save if there are changes
+            sql = (
+                f"UPDATE {self.table} SET " + ",".join(sqlfield) +
+                f" WHERE {self.pk_field}=%s"
+                )
+            values.append(self.pk_value)
+            try:
+                self.dcur.execute(sql, values)
+            except Exception as e:
+                self.db.error = e
+                return False
+        for field in self.fields:
+            self.data[field] = getattr(self, field)
+        return True
+
+    def _insert(self):
+        sql = (
+            "INSERT INTO {} ({}) "
+            "VALUES ({})"
+            ).format(
+                self.table,
+                ','.join(self.fields),
+                ','.join(["%s"] * len(self.fields))
+            )
+        values = []
+        for field in self.fields:
+            newdata = getattr(self, field)
+            values.append(newdata)
+            self.data[field] = newdata
+        try:
+            self.dcur.execute(sql, values)
+        except Exception as e:
+            self.db.error = e
+            return False       
+        self.pk_value = self.dcur.lastrowid
+        return True
+
+    def delete(self, record_id=None):
+        if record_id is None:
+            if self.pk_value is None:
+                return False
+            record_id = self.pk_value
+        sql = "DELETE FROM {} WHERE {}=%s".format(self.table, self.pk_field)
+        try:
+            self.dcur.execute(sql, (record_id,))
+        except Exception as e:
+            self.db.error = e
+            return False
+        if self.dcur.rowcount != 1:
+            return False
+        if self.pk_value == record_id:
+            self.pk_value = None
+            self.clear()
+        return True
+
+    def __str__(self):
+        out = [self.title.format(self.pk_value)]
+        for field in self.fields:
+            value = getattr(self, field, None)
+            out.append(" {:15}: {}".format(field, value))
+        return "\n".join(out)