Use batch database operations instead of one by one to optimze api pulls (#32680)

Resolve #31492

The response time for the Pull Requests API has improved significantly,
dropping from over `2000ms` to about `350ms` on my local machine. It's
about `6` times faster.

A key area for further optimization lies in batch-fetching data for
`apiPullRequest.ChangedFiles, apiPullRequest.Additions, and
apiPullRequest.Deletions`.

Tests `TestAPIViewPulls` does exist and new tests added.

- This PR also fixes some bugs in `GetDiff` functions.
- This PR also fixes data inconsistent in test data. For a pull request,
the head branch's reference should be equal to the reference in
`pull/xxx/head`.

3 files changed, 87 insertions, 10 deletions

diff --git a/tests/integration/api_pull_commits_test.go b/tests/integration/api_pull_commits_test.go
index ad0cb0329c..5ffc8158f3 100644
--- a/tests/integration/api_pull_commits_test.go
+++ b/tests/integration/api_pull_commits_test.go
@@ -33,8 +33,8 @@ func TestAPIPullCommits(t *testing.T) {
 		return
 	}
 
-	assert.Equal(t, "5f22f7d0d95d614d25a5b68592adb345a4b5c7fd", commits[0].SHA)
-	assert.Equal(t, "4a357436d925b5c974181ff12a994538ddc5a269", commits[1].SHA)
+	assert.Equal(t, "985f0301dba5e7b34be866819cd15ad3d8f508ee", commits[0].SHA)
+	assert.Equal(t, "5c050d3b6d2db231ab1f64e324f1b6b9a0b181c2", commits[1].SHA)
 
 	assert.NotEmpty(t, commits[0].Files)
 	assert.NotEmpty(t, commits[1].Files)
diff --git a/tests/integration/api_pull_test.go b/tests/integration/api_pull_test.go
index b7e01d4a20..d26b285a1a 100644
--- a/tests/integration/api_pull_test.go
+++ b/tests/integration/api_pull_test.go
@@ -4,6 +4,8 @@
 package integration
 
 import (
+	"bytes"
+	"context"
 	"fmt"
 	"io"
 	"net/http"
@@ -19,6 +21,7 @@ import (
 	"code.gitea.io/gitea/modules/setting"
 	api "code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/services/forms"
+	"code.gitea.io/gitea/services/gitdiff"
 	issue_service "code.gitea.io/gitea/services/issue"
 	"code.gitea.io/gitea/tests"
 
@@ -41,25 +44,99 @@ func TestAPIViewPulls(t *testing.T) {
 	expectedLen := unittest.GetCount(t, &issues_model.Issue{RepoID: repo.ID}, unittest.Cond("is_pull = ?", true))
 	assert.Len(t, pulls, expectedLen)
 
+	assert.Len(t, pulls, 3)
 	pull := pulls[0]
+	assert.EqualValues(t, 1, pull.Poster.ID)
+	assert.Len(t, pull.RequestedReviewers, 2)
+	assert.Len(t, pull.RequestedReviewersTeams, 0)
+	assert.EqualValues(t, 5, pull.RequestedReviewers[0].ID)
+	assert.EqualValues(t, 6, pull.RequestedReviewers[1].ID)
+	assert.EqualValues(t, 1, pull.ChangedFiles)
+
 	if assert.EqualValues(t, 5, pull.ID) {
 		resp = ctx.Session.MakeRequest(t, NewRequest(t, "GET", pull.DiffURL), http.StatusOK)
-		_, err := io.ReadAll(resp.Body)
+		bs, err := io.ReadAll(resp.Body)
+		assert.NoError(t, err)
+		patch, err := gitdiff.ParsePatch(context.Background(), 1000, 5000, 10, bytes.NewReader(bs), "")
 		assert.NoError(t, err)
-		// TODO: use diff to generate stats to test against
+		if assert.Len(t, patch.Files, pull.ChangedFiles) {
+			assert.Equal(t, "File-WoW", patch.Files[0].Name)
+			// FIXME: The old name should be empty if it's a file add type
+			assert.Equal(t, "File-WoW", patch.Files[0].OldName)
+			assert.EqualValues(t, pull.Additions, patch.Files[0].Addition)
+			assert.EqualValues(t, pull.Deletions, patch.Files[0].Deletion)
+			assert.Equal(t, gitdiff.DiffFileAdd, patch.Files[0].Type)
+		}
 
 		t.Run(fmt.Sprintf("APIGetPullFiles_%d", pull.ID),
 			doAPIGetPullFiles(ctx, pull, func(t *testing.T, files []*api.ChangedFile) {
-				if assert.Len(t, files, 1) {
+				if assert.Len(t, files, pull.ChangedFiles) {
 					assert.Equal(t, "File-WoW", files[0].Filename)
 					assert.Empty(t, files[0].PreviousFilename)
-					assert.EqualValues(t, 1, files[0].Additions)
-					assert.EqualValues(t, 1, files[0].Changes)
-					assert.EqualValues(t, 0, files[0].Deletions)
+					assert.EqualValues(t, pull.Additions, files[0].Additions)
+					assert.EqualValues(t, pull.Deletions, files[0].Deletions)
 					assert.Equal(t, "added", files[0].Status)
 				}
 			}))
 	}
+
+	pull = pulls[1]
+	assert.EqualValues(t, 1, pull.Poster.ID)
+	assert.Len(t, pull.RequestedReviewers, 4)
+	assert.Len(t, pull.RequestedReviewersTeams, 0)
+	assert.EqualValues(t, 3, pull.RequestedReviewers[0].ID)
+	assert.EqualValues(t, 4, pull.RequestedReviewers[1].ID)
+	assert.EqualValues(t, 2, pull.RequestedReviewers[2].ID)
+	assert.EqualValues(t, 5, pull.RequestedReviewers[3].ID)
+	assert.EqualValues(t, 1, pull.ChangedFiles)
+
+	if assert.EqualValues(t, 2, pull.ID) {
+		resp = ctx.Session.MakeRequest(t, NewRequest(t, "GET", pull.DiffURL), http.StatusOK)
+		bs, err := io.ReadAll(resp.Body)
+		assert.NoError(t, err)
+		patch, err := gitdiff.ParsePatch(context.Background(), 1000, 5000, 10, bytes.NewReader(bs), "")
+		assert.NoError(t, err)
+		if assert.Len(t, patch.Files, pull.ChangedFiles) {
+			assert.Equal(t, "README.md", patch.Files[0].Name)
+			assert.Equal(t, "README.md", patch.Files[0].OldName)
+			assert.EqualValues(t, pull.Additions, patch.Files[0].Addition)
+			assert.EqualValues(t, pull.Deletions, patch.Files[0].Deletion)
+			assert.Equal(t, gitdiff.DiffFileChange, patch.Files[0].Type)
+		}
+
+		t.Run(fmt.Sprintf("APIGetPullFiles_%d", pull.ID),
+			doAPIGetPullFiles(ctx, pull, func(t *testing.T, files []*api.ChangedFile) {
+				if assert.Len(t, files, pull.ChangedFiles) {
+					assert.Equal(t, "README.md", files[0].Filename)
+					// FIXME: The PreviousFilename name should be the same as Filename if it's a file change
+					assert.Equal(t, "", files[0].PreviousFilename)
+					assert.EqualValues(t, pull.Additions, files[0].Additions)
+					assert.EqualValues(t, pull.Deletions, files[0].Deletions)
+					assert.Equal(t, "changed", files[0].Status)
+				}
+			}))
+	}
+
+	pull = pulls[2]
+	assert.EqualValues(t, 1, pull.Poster.ID)
+	assert.Len(t, pull.RequestedReviewers, 1)
+	assert.Len(t, pull.RequestedReviewersTeams, 0)
+	assert.EqualValues(t, 1, pull.RequestedReviewers[0].ID)
+	assert.EqualValues(t, 0, pull.ChangedFiles)
+
+	if assert.EqualValues(t, 1, pull.ID) {
+		resp = ctx.Session.MakeRequest(t, NewRequest(t, "GET", pull.DiffURL), http.StatusOK)
+		bs, err := io.ReadAll(resp.Body)
+		assert.NoError(t, err)
+		patch, err := gitdiff.ParsePatch(context.Background(), 1000, 5000, 10, bytes.NewReader(bs), "")
+		assert.NoError(t, err)
+		assert.EqualValues(t, pull.ChangedFiles, patch.NumFiles)
+
+		t.Run(fmt.Sprintf("APIGetPullFiles_%d", pull.ID),
+			doAPIGetPullFiles(ctx, pull, func(t *testing.T, files []*api.ChangedFile) {
+				assert.Len(t, files, pull.ChangedFiles)
+			}))
+	}
 }
 
 func TestAPIViewPullsByBaseHead(t *testing.T) {
diff --git a/tests/integration/pull_commit_test.go b/tests/integration/pull_commit_test.go
index 477f01725d..8d98349fd3 100644
--- a/tests/integration/pull_commit_test.go
+++ b/tests/integration/pull_commit_test.go
@@ -26,8 +26,8 @@ func TestListPullCommits(t *testing.T) {
 		DecodeJSON(t, resp, &pullCommitList)
 
 		if assert.Len(t, pullCommitList.Commits, 2) {
-			assert.Equal(t, "5f22f7d0d95d614d25a5b68592adb345a4b5c7fd", pullCommitList.Commits[0].ID)
-			assert.Equal(t, "4a357436d925b5c974181ff12a994538ddc5a269", pullCommitList.Commits[1].ID)
+			assert.Equal(t, "985f0301dba5e7b34be866819cd15ad3d8f508ee", pullCommitList.Commits[0].ID)
+			assert.Equal(t, "5c050d3b6d2db231ab1f64e324f1b6b9a0b181c2", pullCommitList.Commits[1].ID)
 		}
 		assert.Equal(t, "4a357436d925b5c974181ff12a994538ddc5a269", pullCommitList.LastReviewCommitSha)
 	})