[feature] Implement backfilling statuses thru scheduled_at (#3685)

* Implement backfilling statuses thru scheduled_at

* Forbid mentioning others in backfills

* Update error messages & codes

* Add new tests for backfilled statuses

* Test that backfilling doesn't timeline or notify

* Fix check for absence of notification

* Test that backfills do not cause federation

* Fix type of apimodel.StatusCreateRequest.ScheduledAt in tests

* Add config file switch and min date check

3 files changed, 147 insertions, 14 deletions

diff --git a/internal/api/client/statuses/statuscreate.go b/internal/api/client/statuses/statuscreate.go
index d187e823f..bfb1c486d 100644
--- a/internal/api/client/statuses/statuscreate.go
+++ b/internal/api/client/statuses/statuscreate.go
@@ -179,11 +179,15 @@ import (
 //		x-go-name: ScheduledAt
 //		description: |-
 //			ISO 8601 Datetime at which to schedule a status.
-//			Providing this parameter will cause ScheduledStatus to be returned instead of Status.
+//
+//			Providing this parameter with a *future* time will cause ScheduledStatus to be returned instead of Status.
 //			Must be at least 5 minutes in the future.
+//			This feature isn't implemented yet.
 //
-//			This feature isn't implemented yet; attemping to set it will return 501 Not Implemented.
+//			Providing this parameter with a *past* time will cause the status to be backdated,
+//			and will not push it to the user's followers. This is intended for importing old statuses.
 //		type: string
+//		format: date-time
 //		in: formData
 //	-
 //		name: language
@@ -384,12 +388,6 @@ func parseStatusCreateForm(c *gin.Context) (*apimodel.StatusCreateRequest, gtser
 		return nil, gtserror.NewErrorNotAcceptable(errors.New(text), text)
 	}
 
-	// Check not scheduled status.
-	if form.ScheduledAt != "" {
-		const text = "scheduled_at is not yet implemented"
-		return nil, gtserror.NewErrorNotImplemented(errors.New(text), text)
-	}
-
 	// Check if the deprecated "federated" field was
 	// set in lieu of "local_only", and use it if so.
 	if form.LocalOnly == nil && form.Federated != nil { // nolint:staticcheck
diff --git a/internal/api/client/statuses/statuscreate_test.go b/internal/api/client/statuses/statuscreate_test.go
index 227e7d83e..53e517a6e 100644
--- a/internal/api/client/statuses/statuscreate_test.go
+++ b/internal/api/client/statuses/statuscreate_test.go
@@ -20,14 +20,18 @@ package statuses_test
 import (
 	"bytes"
 	"context"
+	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/suite"
 	"github.com/superseriousbusiness/gotosocial/internal/api/client/statuses"
 	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
+	"github.com/superseriousbusiness/gotosocial/internal/id"
 	"github.com/superseriousbusiness/gotosocial/internal/oauth"
 	"github.com/superseriousbusiness/gotosocial/testrig"
 )
@@ -41,10 +45,11 @@ const (
 	statusMarkdown         = "# Title\n\n## Smaller title\n\nThis is a post written in [markdown](https://www.markdownguide.org/)\n\n<img src=\"https://d33wubrfki0l68.cloudfront.net/f1f475a6fda1c2c4be4cac04033db5c3293032b4/513a4/assets/images/markdown-mark-white.svg\"/>"
 )
 
-func (suite *StatusCreateTestSuite) postStatus(
+// Post a status.
+func (suite *StatusCreateTestSuite) postStatusCore(
 	formData map[string][]string,
 	jsonData string,
-) (string, *httptest.ResponseRecorder) {
+) *httptest.ResponseRecorder {
 	recorder := httptest.NewRecorder()
 	ctx, _ := testrig.CreateGinTestContext(recorder, nil)
 	ctx.Set(oauth.SessionAuthorizedApplication, suite.testApplications["application_1"])
@@ -77,9 +82,42 @@ func (suite *StatusCreateTestSuite) postStatus(
 
 	// Trigger handler.
 	suite.statusModule.StatusCreatePOSTHandler(ctx)
+
+	return recorder
+}
+
+// Post a status and return the result as deterministic JSON.
+func (suite *StatusCreateTestSuite) postStatus(
+	formData map[string][]string,
+	jsonData string,
+) (string, *httptest.ResponseRecorder) {
+	recorder := suite.postStatusCore(formData, jsonData)
 	return suite.parseStatusResponse(recorder)
 }
 
+// Post a status and return the result as a non-deterministic API structure.
+func (suite *StatusCreateTestSuite) postStatusStruct(
+	formData map[string][]string,
+	jsonData string,
+) (*apimodel.Status, *httptest.ResponseRecorder) {
+	recorder := suite.postStatusCore(formData, jsonData)
+
+	result := recorder.Result()
+	defer result.Body.Close()
+
+	data, err := io.ReadAll(result.Body)
+	if err != nil {
+		suite.FailNow(err.Error())
+	}
+
+	apiStatus := apimodel.Status{}
+	if err := json.Unmarshal(data, &apiStatus); err != nil {
+		suite.FailNow(err.Error())
+	}
+
+	return &apiStatus, recorder
+}
+
 // Post a new status with some custom visibility settings
 func (suite *StatusCreateTestSuite) TestPostNewStatus() {
 	out, recorder := suite.postStatus(map[string][]string{
@@ -383,10 +421,98 @@ func (suite *StatusCreateTestSuite) TestPostNewScheduledStatus() {
 
 	// We should have a helpful error message.
 	suite.Equal(`{
-  "error": "Not Implemented: scheduled_at is not yet implemented"
+  "error": "Not Implemented: scheduled statuses are not yet supported"
 }`, out)
 }
 
+func (suite *StatusCreateTestSuite) TestPostNewBackfilledStatus() {
+	// A time in the past.
+	scheduledAtStr := "2020-10-04T15:32:02.018Z"
+	scheduledAt, err := time.Parse(time.RFC3339Nano, scheduledAtStr)
+	if err != nil {
+		suite.FailNow(err.Error())
+	}
+
+	status, recorder := suite.postStatusStruct(map[string][]string{
+		"status":       {"this is a recycled status from the past!"},
+		"scheduled_at": {scheduledAtStr},
+	}, "")
+
+	// Creating a status in the past should succeed.
+	suite.Equal(http.StatusOK, recorder.Code)
+
+	// The status should be backdated.
+	createdAt, err := time.Parse(time.RFC3339Nano, status.CreatedAt)
+	if err != nil {
+		suite.FailNow(err.Error())
+		return
+	}
+	suite.Equal(scheduledAt, createdAt.UTC())
+
+	// The status's ULID should be backdated.
+	timeFromULID, err := id.TimeFromULID(status.ID)
+	if err != nil {
+		suite.FailNow(err.Error())
+		return
+	}
+	suite.Equal(scheduledAt, timeFromULID.UTC())
+}
+
+func (suite *StatusCreateTestSuite) TestPostNewBackfilledStatusWithSelfMention() {
+	_, recorder := suite.postStatus(map[string][]string{
+		"status":       {"@the_mighty_zork this is a recycled mention from the past!"},
+		"scheduled_at": {"2020-10-04T15:32:02.018Z"},
+	}, "")
+
+	// Mentioning yourself is allowed in backfilled statuses.
+	suite.Equal(http.StatusOK, recorder.Code)
+}
+
+func (suite *StatusCreateTestSuite) TestPostNewBackfilledStatusWithMention() {
+	_, recorder := suite.postStatus(map[string][]string{
+		"status":       {"@admin this is a recycled mention from the past!"},
+		"scheduled_at": {"2020-10-04T15:32:02.018Z"},
+	}, "")
+
+	// Mentioning others is forbidden in backfilled statuses.
+	suite.Equal(http.StatusForbidden, recorder.Code)
+}
+
+func (suite *StatusCreateTestSuite) TestPostNewBackfilledStatusWithSelfReply() {
+	_, recorder := suite.postStatus(map[string][]string{
+		"status":         {"this is a recycled reply from the past!"},
+		"scheduled_at":   {"2020-10-04T15:32:02.018Z"},
+		"in_reply_to_id": {suite.testStatuses["local_account_1_status_1"].ID},
+	}, "")
+
+	// Replying to yourself is allowed in backfilled statuses.
+	suite.Equal(http.StatusOK, recorder.Code)
+}
+
+func (suite *StatusCreateTestSuite) TestPostNewBackfilledStatusWithReply() {
+	_, recorder := suite.postStatus(map[string][]string{
+		"status":         {"this is a recycled reply from the past!"},
+		"scheduled_at":   {"2020-10-04T15:32:02.018Z"},
+		"in_reply_to_id": {suite.testStatuses["admin_account_status_1"].ID},
+	}, "")
+
+	// Replying to others is forbidden in backfilled statuses.
+	suite.Equal(http.StatusForbidden, recorder.Code)
+}
+
+func (suite *StatusCreateTestSuite) TestPostNewBackfilledStatusWithPoll() {
+	_, recorder := suite.postStatus(map[string][]string{
+		"status":           {"this is a recycled poll from the past!"},
+		"scheduled_at":     {"2020-10-04T15:32:02.018Z"},
+		"poll[options][]":  {"first option", "second option"},
+		"poll[expires_in]": {"3600"},
+		"poll[multiple]":   {"true"},
+	}, "")
+
+	// Polls are forbidden in backfilled statuses.
+	suite.Equal(http.StatusForbidden, recorder.Code)
+}
+
 func (suite *StatusCreateTestSuite) TestPostNewStatusMarkdown() {
 	out, recorder := suite.postStatus(map[string][]string{
 		"status":       {statusMarkdown},
diff --git a/internal/api/model/status.go b/internal/api/model/status.go
index ea9fbaa35..2ee3123e6 100644
--- a/internal/api/model/status.go
+++ b/internal/api/model/status.go
@@ -17,7 +17,11 @@
 
 package model
 
-import "github.com/superseriousbusiness/gotosocial/internal/language"
+import (
+	"time"
+
+	"github.com/superseriousbusiness/gotosocial/internal/language"
+)
 
 // Status models a status or post.
 //
@@ -231,9 +235,14 @@ type StatusCreateRequest struct {
 	Federated *bool `form:"federated" json:"federated"`
 
 	// ISO 8601 Datetime at which to schedule a status.
-	// Providing this parameter will cause ScheduledStatus to be returned instead of Status.
+	//
+	// Providing this parameter with a *future* time will cause ScheduledStatus to be returned instead of Status.
 	// Must be at least 5 minutes in the future.
-	ScheduledAt string `form:"scheduled_at" json:"scheduled_at"`
+	// This feature isn't implemented yet.
+	//
+	// Providing this parameter with a *past* time will cause the status to be backdated,
+	// and will not push it to the user's followers. This is intended for importing old statuses.
+	ScheduledAt *time.Time `form:"scheduled_at" json:"scheduled_at"`
 
 	// ISO 639 language code for this status.
 	Language string `form:"language" json:"language"`