From 3170e1abd5558039811f80031727f43eb07e8294 Mon Sep 17 00:00:00 2001
From: OBrutus <vaishnavani7@gmail.com>
Date: Sat, 13 Jun 2026 23:36:30 +0530
Subject: [PATCH] feat: implement AtCoder platform support with URL extraction
 and testing

---
 src/platform/atcoder/atcoder.go      | 76 ++++++++++++++++++++++++++++
 src/platform/atcoder/atcoder_test.go | 35 +++++++++++++
 src/platform/identifier.go           |  3 ++
 3 files changed, 114 insertions(+)
 create mode 100644 src/platform/atcoder/atcoder.go
 create mode 100644 src/platform/atcoder/atcoder_test.go

diff --git a/src/platform/atcoder/atcoder.go b/src/platform/atcoder/atcoder.go
new file mode 100644
index 0000000..54d8c32
--- /dev/null
+++ b/src/platform/atcoder/atcoder.go
@@ -0,0 +1,76 @@
+package atcoder
+
+import (
+	"errors"
+	"prepare-code/src/constants"
+	"prepare-code/src/types"
+	"strings"
+)
+
+var ErrInvalidAtCoderUrl = errors.New("invalid url of AtCoder")
+
+const urlFormat string = "https://atcoder.jp/contests/abc461/tasks/abc461_a"
+
+const codeNameDelimiter string = "-"
+
+type AtCoderPlatform struct {
+	name     types.PlatformName
+	codeName string
+}
+
+func (ac AtCoderPlatform) GetPlatformName() types.PlatformName {
+	return constants.PlatformAtCoder
+}
+
+func (ac AtCoderPlatform) GetCodeName() string {
+	return ac.codeName
+}
+
+func (ac AtCoderPlatform) GetPlatform(url string) (types.Platform, error) {
+	return GetPlatform(url)
+}
+
+// This is the main method
+func GetPlatform(url string) (types.Platform, error) {
+	extractedCodeName, err := extractCodeName(url)
+	if err != nil {
+		return nil, err
+	}
+
+	return AtCoderPlatform{
+		name:     constants.PlatformCodeforces,
+		codeName: extractedCodeName, // placeholder for actual extraction logic
+	}, nil
+}
+
+func extractCodeName(url string) (string, error) {
+	// https://atcoder.jp/contests/abc461/tasks/abc461_a
+	if len(url) < len("atcoder.jp") {
+		return "", ErrInvalidAtCoderUrl
+	}
+
+	i := 0
+	const prefix string = "atcoder.jp/contests/"
+	for i+len(prefix) < len(url) {
+		if url[i:i+len(prefix)] == prefix {
+			break
+		}
+		i++
+	}
+
+	i += len(prefix)
+	if i == len(url) {
+		return "", ErrInvalidAtCoderUrl
+	}
+
+	prefixRemovedString := url[i:]
+	suffix := strings.Split(prefixRemovedString, "/")
+	if len(suffix) < 3 {
+		return "", ErrInvalidAtCoderUrl
+	}
+
+	// contestNumber := suffix[0]
+	qeustionCode := strings.ToUpper(suffix[2])
+
+	return qeustionCode, nil
+}
diff --git a/src/platform/atcoder/atcoder_test.go b/src/platform/atcoder/atcoder_test.go
new file mode 100644
index 0000000..cbcdda6
--- /dev/null
+++ b/src/platform/atcoder/atcoder_test.go
@@ -0,0 +1,35 @@
+package atcoder
+
+import "testing"
+
+func TestSimpleCodeExtraction(t *testing.T) {
+	testCases := []struct {
+		name string
+		url  string
+		code string
+		err  error
+	}{
+		{name: "Positive Test Case", url: "https://atcoder.jp/contests/abc461/tasks/abc461_a", code: "ABC461_A", err: nil},
+		{name: "Test Case 1", url: "https://atcoder.jp/contests/abc461/tasks/", err: ErrInvalidAtCoderUrl},
+		{name: "Test Case 2", url: "https://atcoder.jp/contests/abc461/tasks", err: ErrInvalidAtCoderUrl},
+		{name: "Test Case 3", url: "https://atcoder.jp/contests/abc461/", err: ErrInvalidAtCoderUrl},
+		{name: "Test Case 4", url: "https://atcoder.jp/contests/abc461", err: ErrInvalidAtCoderUrl},
+		{name: "Test Case 5", url: "https://atcoder.jp/contests/", err: ErrInvalidAtCoderUrl},
+		{name: "Test Case 6", url: "https://atcoder/contests/", err: ErrInvalidAtCoderUrl},
+	}
+
+	for _, tt := range testCases {
+		t.Run(tt.name, func(t *testing.T) {
+			code, err := extractCodeName(tt.url)
+			if (err != nil && tt.err != nil) && err != tt.err {
+				t.Errorf("Test Failed for %s. Got=%v Expected=%v", tt.name, err, tt.err)
+				return
+			}
+
+			if code != tt.code {
+				t.Errorf("Test Failed for %s. Got=%v Expected=%v", tt.name, code, tt.code)
+				return
+			}
+		})
+	}
+}
diff --git a/src/platform/identifier.go b/src/platform/identifier.go
index 5e9a91d..fbb8a47 100644
--- a/src/platform/identifier.go
+++ b/src/platform/identifier.go
@@ -2,6 +2,7 @@ package platform
 
 import (
 	"errors"
+	"prepare-code/src/platform/atcoder"
 	"prepare-code/src/platform/codeforces"
 	"prepare-code/src/platform/leetcode"
 	"prepare-code/src/types"
@@ -20,6 +21,8 @@ func GetPlatform(url string) (types.Platform, error) {
 		return codeforces.GetPlatform(url)
 	} else if strings.Contains(url, "leetcode.com") {
 		return leetcode.GetPlatform(url)
+	} else if strings.Contains(url, "atcoder.jp") {
+		return atcoder.GetPlatform(url)
 	} else {
 		return nil, errors.New("unknown platform or platform not supported")
 	}