feat: workflowpattern package (#1618)

* feat: workflowpattern package

* nolint:gocyclo

---------

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

pkg/workflowpattern/trace_writer.go

@@ -0,0 +1,18 @@
+package workflowpattern
+
+import "fmt"
+
+type TraceWriter interface {
+	Info(string, ...interface{})
+}
+
+type EmptyTraceWriter struct{}
+
+func (*EmptyTraceWriter) Info(string, ...interface{}) {
+}
+
+type StdOutTraceWriter struct{}
+
+func (*StdOutTraceWriter) Info(format string, args ...interface{}) {
+	fmt.Printf(format+"\n", args...)
+}

pkg/workflowpattern/workflow_pattern.go

@@ -0,0 +1,196 @@
+package workflowpattern
+
+import (
+	"fmt"
+	"regexp"
+	"strings"
+)
+
+type WorkflowPattern struct {
+	Pattern  string
+	Negative bool
+	Regex    *regexp.Regexp
+}
+
+func CompilePattern(rawpattern string) (*WorkflowPattern, error) {
+	negative := false
+	pattern := rawpattern
+	if strings.HasPrefix(rawpattern, "!") {
+		negative = true
+		pattern = rawpattern[1:]
+	}
+	rpattern, err := PatternToRegex(pattern)
+	if err != nil {
+		return nil, err
+	}
+	regex, err := regexp.Compile(rpattern)
+	if err != nil {
+		return nil, err
+	}
+	return &WorkflowPattern{
+		Pattern:  pattern,
+		Negative: negative,
+		Regex:    regex,
+	}, nil
+}
+
+//nolint:gocyclo
+func PatternToRegex(pattern string) (string, error) {
+	var rpattern strings.Builder
+	rpattern.WriteString("^")
+	pos := 0
+	errors := map[int]string{}
+	for pos < len(pattern) {
+		switch pattern[pos] {
+		case '*':
+			if pos+1 < len(pattern) && pattern[pos+1] == '*' {
+				if pos+2 < len(pattern) && pattern[pos+2] == '/' {
+					rpattern.WriteString("(.+/)?")
+					pos += 3
+				} else {
+					rpattern.WriteString(".*")
+					pos += 2
+				}
+			} else {
+				rpattern.WriteString("[^/]*")
+				pos++
+			}
+		case '+', '?':
+			if pos > 0 {
+				rpattern.WriteByte(pattern[pos])
+			} else {
+				rpattern.WriteString(regexp.QuoteMeta(string([]byte{pattern[pos]})))
+			}
+			pos++
+		case '[':
+			rpattern.WriteByte(pattern[pos])
+			pos++
+			if pos < len(pattern) && pattern[pos] == ']' {
+				errors[pos] = "Unexpected empty brackets '[]'"
+				pos++
+				break
+			}
+			validChar := func(a, b, test byte) bool {
+				return test >= a && test <= b
+			}
+			startPos := pos
+			for pos < len(pattern) && pattern[pos] != ']' {
+				switch pattern[pos] {
+				case '-':
+					if pos <= startPos || pos+1 >= len(pattern) {
+						errors[pos] = "Invalid range"
+						pos++
+						break
+					}
+					validRange := func(a, b byte) bool {
+						return validChar(a, b, pattern[pos-1]) && validChar(a, b, pattern[pos+1]) && pattern[pos-1] <= pattern[pos+1]
+					}
+					if !validRange('A', 'z') && !validRange('0', '9') {
+						errors[pos] = "Ranges can only include a-z, A-Z, A-z, and 0-9"
+						pos++
+						break
+					}
+					rpattern.WriteString(pattern[pos : pos+2])
+					pos += 2
+				default:
+					if !validChar('A', 'z', pattern[pos]) && !validChar('0', '9', pattern[pos]) {
+						errors[pos] = "Ranges can only include a-z, A-Z and 0-9"
+						pos++
+						break
+					}
+					rpattern.WriteString(regexp.QuoteMeta(string([]byte{pattern[pos]})))
+					pos++
+				}
+			}
+			if pos >= len(pattern) || pattern[pos] != ']' {
+				errors[pos] = "Missing closing bracket ']' after '['"
+				pos++
+			}
+			rpattern.WriteString("]")
+			pos++
+		case '\\':
+			if pos+1 >= len(pattern) {
+				errors[pos] = "Missing symbol after \\"
+				pos++
+				break
+			}
+			rpattern.WriteString(regexp.QuoteMeta(string([]byte{pattern[pos+1]})))
+			pos += 2
+		default:
+			rpattern.WriteString(regexp.QuoteMeta(string([]byte{pattern[pos]})))
+			pos++
+		}
+	}
+	if len(errors) > 0 {
+		var errorMessage strings.Builder
+		for position, err := range errors {
+			if errorMessage.Len() > 0 {
+				errorMessage.WriteString(", ")
+			}
+			errorMessage.WriteString(fmt.Sprintf("Position: %d Error: %s", position, err))
+		}
+		return "", fmt.Errorf("invalid Pattern '%s': %s", pattern, errorMessage.String())
+	}
+	rpattern.WriteString("$")
+	return rpattern.String(), nil
+}
+
+func CompilePatterns(patterns ...string) ([]*WorkflowPattern, error) {
+	ret := []*WorkflowPattern{}
+	for _, pattern := range patterns {
+		cp, err := CompilePattern(pattern)
+		if err != nil {
+			return nil, err
+		}
+		ret = append(ret, cp)
+	}
+	return ret, nil
+}
+
+// returns true if the workflow should be skipped paths/branches
+func Skip(sequence []*WorkflowPattern, input []string, traceWriter TraceWriter) bool {
+	if len(sequence) == 0 {
+		return false
+	}
+	for _, file := range input {
+		matched := false
+		for _, item := range sequence {
+			if item.Regex.MatchString(file) {
+				pattern := item.Pattern
+				if item.Negative {
+					matched = false
+					traceWriter.Info("%s excluded by pattern %s", file, pattern)
+				} else {
+					matched = true
+					traceWriter.Info("%s included by pattern %s", file, pattern)
+				}
+			}
+		}
+		if matched {
+			return false
+		}
+	}
+	return true
+}
+
+// returns true if the workflow should be skipped paths-ignore/branches-ignore
+func Filter(sequence []*WorkflowPattern, input []string, traceWriter TraceWriter) bool {
+	if len(sequence) == 0 {
+		return false
+	}
+	for _, file := range input {
+		matched := false
+		for _, item := range sequence {
+			if item.Regex.MatchString(file) == !item.Negative {
+				pattern := item.Pattern
+				traceWriter.Info("%s ignored by pattern %s", file, pattern)
+				matched = true
+				break
+			}
+		}
+		if !matched {
+			return false
+		}
+	}
+	return true
+}