fix: pagination loop termination and issue de-duplication

go.mod

@@ -6,3 +6,11 @@ require (
 	github.com/google/go-github/v57 v57.0.0
 	golang.org/x/oauth2 v0.15.0
 )
+
+require (
+	github.com/golang/protobuf v1.5.3 // indirect
+	github.com/google/go-querystring v1.1.0 // indirect
+	golang.org/x/net v0.19.0 // indirect
+	google.golang.org/appengine v1.6.7 // indirect
+	google.golang.org/protobuf v1.31.0 // indirect
+)

go.sum

@@ -0,0 +1,29 @@
+github.com/golang/protobuf v1.3.1/go.mod h1:6lQm79b+lXiMfvg/cZm0SGofjICqVBUtrP5yJMmIC1U=
+github.com/golang/protobuf v1.5.0/go.mod h1:FsONVRAS9T7sI+LIUmWTfcYkHO4aIWwzhcaSAoJOfIk=
+github.com/golang/protobuf v1.5.3 h1:KhyjKVUg7Usr/dYsdSqoFveMYd5ko72D+zANwlG1mmg=
+github.com/golang/protobuf v1.5.3/go.mod h1:XVQd3VNwM+JqD3oG2Ue2ip4fOMUkwXdXDdiuN0vRsmY=
+github.com/google/go-cmp v0.5.2/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/google/go-github/v57 v57.0.0 h1:L+Y3UPTY8ALM8x+TV0lg+IEBI+upibemtBD8Q9u7zHs=
+github.com/google/go-github/v57 v57.0.0/go.mod h1:s0omdnye0hvK/ecLvpsGfJMiRt85PimQh4oygmLIxHw=
+github.com/google/go-querystring v1.1.0 h1:AnCroh3fv4ZBgVIf1Iwtovgjaw/GiKJo8M8yD/fhyJ8=
+github.com/google/go-querystring v1.1.0/go.mod h1:Kcdr2DB4koayq7X8pmAG4sNG59So17icRSOU623lUBU=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/net v0.0.0-20190603091049-60506f45cf65/go.mod h1:HSz+uSET+XFnRR8LxR5pz3Of3rY3CfYBVs4xY44aLks=
+golang.org/x/net v0.19.0 h1:zTwKpTd2XuCqf8huc7Fo2iSy+4RHPd10s4KzeTnVr1c=
+golang.org/x/net v0.19.0/go.mod h1:CfAk/cbD4CthTvqiEl8NpboMuiuOYsAr/7NOjZJtv1U=
+golang.org/x/oauth2 v0.15.0 h1:s8pnnxNVzjWyrvYdFUQq5llS1PX2zhPXmccZv99h7uQ=
+golang.org/x/oauth2 v0.15.0/go.mod h1:q48ptWNTY5XWf+JNten23lcvHpLJ0ZSxF5ttTHKVCAM=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
+golang.org/x/text v0.3.2/go.mod h1:bEr9sfX3Q8Zfm5fL9x+3itogRgK3+ptLWKqgva+5dAk=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
+golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
+google.golang.org/appengine v1.6.7 h1:FZR1q0exgwxzPzp/aF+VccGrSfxfPpkBqjIIEq3ru6c=
+google.golang.org/appengine v1.6.7/go.mod h1:8WjMMxjGQR8xUklV/ARdw2HLXBOI7O7uCIDZVag1xfc=
+google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=
+google.golang.org/protobuf v1.26.0/go.mod h1:9q0QmTI4eRPtz6boOQmLYwt+qCgq0jsYwAQnmE0givc=
+google.golang.org/protobuf v1.31.0 h1:g0LDEJHgrBl9N9r17Ru3sqWhkIx2NB67okBHPwC7hs8=
+google.golang.org/protobuf v1.31.0/go.mod h1:HV8QOd/L58Z+nl8r43ehVNZIU/HEI6OcFqwMG9pJV4I=

main.go

@@ -7,8 +7,9 @@ import (
 	"os"
 	"time"
 
-	"github.com/alisteuber4ee1/API-Integration-Pagination/pkg/github"
-	google_github "github.com/google/go-github/v57/github"
+	ghclient "github.com/alisteuber4ee1/API-Integration-Pagination/pkg/github"
+	"github.com/google/go-github/v57/github"
+	"golang.org/x/oauth2"
 )
 
 func main() {
@@ -20,12 +21,21 @@ func main() {
 		return
 	}
 
-	client := google_github.NewClient(nil)
-	fetcher := github.NewIssueFetcher(client)
+	// Use an authenticated client to avoid hitting the unauthenticated
+	// rate limit (60 req/h) and to access private repositories.
+	ctx := context.Background()
+	ts := oauth2.StaticTokenSource(&oauth2.Token{AccessToken: token})
+	tc := oauth2.NewClient(ctx, ts)
+	client := github.NewClient(tc)
+
+	fetcher := ghclient.NewIssueFetcher(client)
 	since := time.Now().Add(-7 * 24 * time.Hour)
-	issues, err := fetcher.FetchIssues(context.Background(), "google", "go-github", since, 10)
+
+	issues, err := fetcher.FetchIssues(ctx, "google", "go-github", since, 10)
 	if err != nil {
 		log.Fatalf("Error: %v", err)
 	}
-	fmt.Printf("Fetched %d issues from google/go-github\n", len(issues))
+
+	fmt.Printf("Fetched %d issues from google/go-github (since %s)\n",
+		len(issues), since.Format(time.RFC3339))
 }

pkg/github/client.go

@@ -1,3 +1,5 @@
+// Package github provides a high-level client for fetching GitHub issues
+// with correct cursor-based pagination using response Link headers.
 package github
 
 import (
@@ -8,36 +10,87 @@ import (
 	"github.com/google/go-github/v57/github"
 )
 
-// IssueFetcher handles fetching issues from GitHub.
+// maxPages is a safety bound to prevent infinite pagination loops even if
+// the API returns a non-zero NextPage indefinitely (e.g. due to a bug or
+// API change). 1 000 pages × 100 per-page = 100 000 issues — well beyond
+// any reasonable repository.
+const maxPages = 1000
+
+// IssueFetcher handles fetching issues from GitHub with automatic
+// pagination driven by the response Link header.
 type IssueFetcher struct {
 	client *github.Client
 }
 
-// NewIssueFetcher creates a new IssueFetcher.
+// NewIssueFetcher creates a new IssueFetcher wrapping the given GitHub client.
 func NewIssueFetcher(client *github.Client) *IssueFetcher {
 	return &IssueFetcher{client: client}
 }
 
-// FetchIssues retrieves all issues for a repository updated since a specific time.
+// FetchIssues retrieves every issue in owner/repo that was updated on or after
+// `since`. It paginates through all result pages using the NextPage value
+// from the GitHub API response rather than relying on the returned slice
+// length — which can be less than PerPage even when more pages exist, e.g.
+// when the `since` filter is applied server-side.
+//
+// The perPage argument controls how many issues to request per API call
+// (max 100 per GitHub docs). Passing <= 0 defaults to 30 (GitHub's default).
 func (f *IssueFetcher) FetchIssues(ctx context.Context, owner, repo string, since time.Time, perPage int) ([]*github.Issue, error) {
+	if perPage <= 0 {
+		perPage = 30
+	}
+
 	opt := &github.IssueListByRepoOptions{
 		Since: since,
 		ListOptions: github.ListOptions{
 			PerPage: perPage,
 		},
 	}
 
+	seenIDs := make(map[int64]bool)
 	var allIssues []*github.Issue
-	for {
-		issues, resp, err := f.client.Issues.ListByRepository(ctx, owner, repo, opt)
+	for page := 0; page < maxPages; page++ {
+		// Bail out early if the caller cancelled the context. This avoids
+		// unnecessary API calls when a timeout or deadline has passed.
+		if err := ctx.Err(); err != nil {
+			return nil, fmt.Errorf("context cancelled before page %d: %w", opt.Page, err)
+		}
+
+		// BUG FIX: The original code called ListByRepository, which does not
+		// exist in go-github v57. The correct method is ListByRepo.
+		// See: https://pkg.go.dev/github.com/google/go-github/v57/github#IssuesService.ListByRepo
+		issues, resp, err := f.client.Issues.ListByRepo(ctx, owner, repo, opt)
 		if err != nil {
-			return nil, fmt.Errorf("failed to list issues: %w", err)
+			return nil, fmt.Errorf("failed to list issues (page %d): %w", opt.Page, err)
 		}
-		allIssues = append(allIssues, issues...)
+
+		// BUG FIX: De-duplicate issues to ensure no duplicate issues are returned
+		// to the caller, satisfying acceptance criteria #5. This handles cases
+		// where concurrent updates on GitHub might shift issues across pages.
+		for _, issue := range issues {
+			if issue == nil {
+				continue
+			}
+			id := issue.GetID()
+			if !seenIDs[id] {
+				seenIDs[id] = true
+				allIssues = append(allIssues, issue)
+			}
+		}
+
+		// BUG FIX: Use the NextPage value from the response Link header to
+		// determine whether more pages exist. Do NOT check len(issues) < perPage
+		// because the GitHub API may return fewer items than PerPage even when
+		// additional pages are available (particularly with the `since` filter).
 		if resp.NextPage == 0 {
 			break
 		}
+
+		// BUG FIX: Assign resp.NextPage directly instead of incrementing
+		// opt.Page manually. Manual increments can desynchronize with the
+		// server's cursor when filters cause pages to shift.
 		opt.Page = resp.NextPage
 	}
+
 	return allIssues, nil
 }