From e2fa537163da74b3c518ac27cffeb97452825228 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Edgar=20Ram=C3=ADrez-Mondrag=C3=B3n?= <edgarrm358@gmail.com>
Date: Tue, 17 Sep 2024 11:49:48 -0600
Subject: [PATCH] Incremental replication

---
 samples/sample_tap_csv/client.py | 43 ++++++++++++++++++++++++++------
 1 file changed, 36 insertions(+), 7 deletions(-)

diff --git a/samples/sample_tap_csv/client.py b/samples/sample_tap_csv/client.py
index 15e493bfe..a35fd3510 100644
--- a/samples/sample_tap_csv/client.py
+++ b/samples/sample_tap_csv/client.py
@@ -1,18 +1,28 @@
 from __future__ import annotations
 
 import csv
+import datetime
+import os
 import typing as t
 
 from singer_sdk import Stream
+from singer_sdk.streams.core import REPLICATION_INCREMENTAL
 
 if t.TYPE_CHECKING:
     from singer_sdk.helpers.types import Context, Record
     from singer_sdk.tap_base import Tap
 
-SDC_META_FILEPATH = "_sdc_file"
+SDC_META_FILEPATH = "_sdc_path"
+SDC_META_MODIFIED_AT = "_sdc_modified_at"
+
+
+def _to_datetime(value: float) -> str:
+    return datetime.datetime.fromtimestamp(value).astimezone()
 
 
 class CSVStream(Stream):
+    """CSV stream class."""
+
     def __init__(
         self,
         tap: Tap,
@@ -25,23 +35,23 @@ def __init__(
             "type": ["object"],
             "properties": {
                 SDC_META_FILEPATH: {"type": "string"},
+                SDC_META_MODIFIED_AT: {"type": "string", "format": "date-time"},
             },
             "required": [],
             "additionalProperties": {"type": "string"},
         }
         super().__init__(tap, schema, name)
+
+        # TODO(edgarrmondragon): Make this None if the filesytem does not support it.
+        self.replication_key = SDC_META_MODIFIED_AT
+
         self._partitions = partitions or []
 
     @property
     def partitions(self) -> list[Context]:
         return self._partitions
 
-    def get_records(  # noqa: PLR6301
-        self,
-        context: Context | None,
-    ) -> t.Iterable[Record | tuple[Record, Context | None]]:
-        path: str = context[SDC_META_FILEPATH]
-
+    def _read_file(self, path: str) -> t.Iterable[Record]:  # noqa: PLR6301
         # Make these configurable.
         delimiter = ","
         quotechar = '"'
@@ -60,3 +70,22 @@ def get_records(  # noqa: PLR6301
                 lineterminator=lineterminator,
             )
             yield from reader
+
+    def get_records(
+        self,
+        context: Context | None,
+    ) -> t.Iterable[Record | tuple[Record, Context | None]]:
+        path: str = context[SDC_META_FILEPATH]
+        mtime = os.path.getmtime(path)  # noqa: PTH204
+
+        if (
+            self.replication_method is REPLICATION_INCREMENTAL
+            and (previous_bookmark := self.get_starting_timestamp(context))
+            and _to_datetime(mtime) < previous_bookmark
+        ):
+            self.logger.info("File has not been modified since last read, skipping")
+            return
+
+        for record in self._read_file(path):
+            record[SDC_META_MODIFIED_AT] = _to_datetime(mtime)
+            yield record