feat: add pull request linting action and validation logic

internal/validation/validation.go

@@ -0,0 +1,83 @@
+package validation
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+func ValidateConventionalCommit(commit string) error {
+	// Regex to match the commit format
+	// type(scope)!: description
+	// or
+	// type!: description
+	// or
+	// type: description
+	re := regexp.MustCompile(`^(?P<type>[a-z]+)(?P<scope>\([a-z]+\))?(?P<breaking>!)?: (?P<description>[a-z].+)$`)
+	match := re.FindStringSubmatch(commit)
+
+	if len(match) == 0 {
+		return fmt.Errorf("invalid commit format")
+	}
+
+	typeIndex := re.SubexpIndex("type")
+	scopeIndex := re.SubexpIndex("scope")
+	breakingIndex := re.SubexpIndex("breaking")
+	descriptionIndex := re.SubexpIndex("description")
+
+	commitType := match[typeIndex]
+	scope := match[scopeIndex]
+	breaking := match[breakingIndex]
+	description := match[descriptionIndex]
+
+	// Type MUST be lowercase
+	if commitType != strings.ToLower(commitType) {
+		return fmt.Errorf("type must be lowercase")
+	}
+
+	// Description MUST start with lowercase
+	if description != strings.ToLower(description) {
+		return fmt.Errorf("description must start with lowercase")
+	}
+
+	// Scope MUST be lowercase
+	if scope != "" && scope != strings.ToLower(scope) {
+		return fmt.Errorf("scope must be lowercase")
+	}
+
+	// Check for breaking change indicator
+	hasBreakingChangeFooter := strings.Contains(commit, "BREAKING CHANGE:")
+	if breaking == "!" && hasBreakingChangeFooter {
+		return fmt.Errorf("breaking change indicator and footer are mutually exclusive")
+	}
+
+	lines := strings.Split(commit, "\n")
+	if len(lines) > 1 {
+		body := strings.Join(lines[1:], "\n")
+		// Check if body is separated from description by a blank line
+		if !strings.HasPrefix(body, "\n") {
+			return fmt.Errorf("body must be separated from description by a blank line")
+		}
+	}
+
+	// Check for footers
+	footerRegex := regexp.MustCompile(`(?m)^(?P<token>[A-Za-z-]+|BREAKING CHANGE): (?P<value>.*)$`)
+	footerMatches := footerRegex.FindAllStringSubmatch(commit, -1)
+
+	for _, footerMatch := range footerMatches {
+		tokenIndex := footerRegex.SubexpIndex("token")
+		token := footerMatch[tokenIndex]
+
+		// BREAKING-CHANGE MUST be synonymous with BREAKING CHANGE
+		if token == "BREAKING-CHANGE" {
+			continue
+		}
+
+		// Token MUST use - in place of whitespace characters, except for BREAKING CHANGE
+		if token != "BREAKING CHANGE" && strings.Contains(token, " ") {
+			return fmt.Errorf("footer token must use - in place of whitespace characters")
+		}
+	}
+
+	return nil
+}