Merge pull request golang#213 from carolynvs/lockdiff

Move LockDiff from dep into gps

lockdiff.go

@@ -0,0 +1,253 @@
+package gps
+
+import (
+	"encoding/hex"
+	"fmt"
+	"sort"
+	"strings"
+)
+
+// StringDiff represents a modified string value.
+// * Added: Previous = nil, Current != nil
+// * Deleted: Previous != nil, Current = nil
+// * Modified: Previous != nil, Current != nil
+// * No Change: Previous = Current, or a nil pointer
+type StringDiff struct {
+	Previous string
+	Current  string
+}
+
+func (diff *StringDiff) String() string {
+	if diff == nil {
+		return ""
+	}
+
+	if diff.Previous == "" && diff.Current != "" {
+		return fmt.Sprintf("+ %s", diff.Current)
+	}
+
+	if diff.Previous != "" && diff.Current == "" {
+		return fmt.Sprintf("- %s", diff.Previous)
+	}
+
+	if diff.Previous != diff.Current {
+		return fmt.Sprintf("%s -> %s", diff.Previous, diff.Current)
+	}
+
+	return diff.Current
+}
+
+// LockDiff is the set of differences between an existing lock file and an updated lock file.
+// Fields are only populated when there is a difference, otherwise they are empty.
+type LockDiff struct {
+	HashDiff *StringDiff
+	Add      []LockedProjectDiff
+	Remove   []LockedProjectDiff
+	Modify   []LockedProjectDiff
+}
+
+// LockedProjectDiff contains the before and after snapshot of a project reference.
+// Fields are only populated when there is a difference, otherwise they are empty.
+type LockedProjectDiff struct {
+	Name     ProjectRoot
+	Source   *StringDiff
+	Version  *StringDiff
+	Branch   *StringDiff
+	Revision *StringDiff
+	Packages []StringDiff
+}
+
+// DiffLocks compares two locks and identifies the differences between them.
+// Returns nil if there are no differences.
+func DiffLocks(l1 Lock, l2 Lock) *LockDiff {
+	// Default nil locks to empty locks, so that we can still generate a diff
+	if l1 == nil {
+		l1 = &SimpleLock{}
+	}
+	if l2 == nil {
+		l2 = &SimpleLock{}
+	}
+
+	p1, p2 := l1.Projects(), l2.Projects()
+
+	// Check if the slices are sorted already. If they are, we can compare
+	// without copying. Otherwise, we have to copy to avoid altering the
+	// original input.
+	sp1, sp2 := lpsorter(p1), lpsorter(p2)
+	if len(p1) > 1 && !sort.IsSorted(sp1) {
+		p1 = make([]LockedProject, len(p1))
+		copy(p1, l1.Projects())
+		sort.Sort(lpsorter(p1))
+	}
+	if len(p2) > 1 && !sort.IsSorted(sp2) {
+		p2 = make([]LockedProject, len(p2))
+		copy(p2, l2.Projects())
+		sort.Sort(lpsorter(p2))
+	}
+
+	diff := LockDiff{}
+
+	h1 := hex.EncodeToString(l1.InputHash())
+	h2 := hex.EncodeToString(l2.InputHash())
+	if h1 != h2 {
+		diff.HashDiff = &StringDiff{Previous: h1, Current: h2}
+	}
+
+	var i2next int
+	for i1 := 0; i1 < len(p1); i1++ {
+		lp1 := p1[i1]
+		pr1 := lp1.pi.ProjectRoot
+
+		var matched bool
+		for i2 := i2next; i2 < len(p2); i2++ {
+			lp2 := p2[i2]
+			pr2 := lp2.pi.ProjectRoot
+
+			switch strings.Compare(string(pr1), string(pr2)) {
+			case 0: // Found a matching project
+				matched = true
+				pdiff := DiffProjects(lp1, lp2)
+				if pdiff != nil {
+					diff.Modify = append(diff.Modify, *pdiff)
+				}
+				i2next = i2 + 1 // Don't evaluate to this again
+			case +1: // Found a new project
+				add := buildLockedProjectDiff(lp2)
+				diff.Add = append(diff.Add, add)
+				i2next = i2 + 1 // Don't evaluate to this again
+				continue        // Keep looking for a matching project
+			case -1: // Project has been removed, handled below
+				break
+			}
+
+			break // Done evaluating this project, move onto the next
+		}
+
+		if !matched {
+			remove := buildLockedProjectDiff(lp1)
+			diff.Remove = append(diff.Remove, remove)
+		}
+	}
+
+	// Anything that still hasn't been evaluated are adds
+	for i2 := i2next; i2 < len(p2); i2++ {
+		lp2 := p2[i2]
+		add := buildLockedProjectDiff(lp2)
+		diff.Add = append(diff.Add, add)
+	}
+
+	if diff.HashDiff == nil && len(diff.Add) == 0 && len(diff.Remove) == 0 && len(diff.Modify) == 0 {
+		return nil // The locks are the equivalent
+	}
+	return &diff
+}
+
+func buildLockedProjectDiff(lp LockedProject) LockedProjectDiff {
+	s2 := lp.pi.Source
+	r2, b2, v2 := VersionComponentStrings(lp.Version())
+
+	var rev, version, branch, source *StringDiff
+	if s2 != "" {
+		source = &StringDiff{Previous: s2, Current: s2}
+	}
+	if r2 != "" {
+		rev = &StringDiff{Previous: r2, Current: r2}
+	}
+	if b2 != "" {
+		branch = &StringDiff{Previous: b2, Current: b2}
+	}
+	if v2 != "" {
+		version = &StringDiff{Previous: v2, Current: v2}
+	}
+
+	add := LockedProjectDiff{
+		Name:     lp.pi.ProjectRoot,
+		Source:   source,
+		Revision: rev,
+		Version:  version,
+		Branch:   branch,
+		Packages: make([]StringDiff, len(lp.Packages())),
+	}
+	for i, pkg := range lp.Packages() {
+		add.Packages[i] = StringDiff{Previous: pkg, Current: pkg}
+	}
+	return add
+}
+
+// DiffProjects compares two projects and identifies the differences between them.
+// Returns nil if there are no differences
+func DiffProjects(lp1 LockedProject, lp2 LockedProject) *LockedProjectDiff {
+	diff := LockedProjectDiff{Name: lp1.pi.ProjectRoot}
+
+	s1 := lp1.pi.Source
+	s2 := lp2.pi.Source
+	if s1 != s2 {
+		diff.Source = &StringDiff{Previous: s1, Current: s2}
+	}
+
+	r1, b1, v1 := VersionComponentStrings(lp1.Version())
+	r2, b2, v2 := VersionComponentStrings(lp2.Version())
+	if r1 != r2 {
+		diff.Revision = &StringDiff{Previous: r1, Current: r2}
+	}
+	if b1 != b2 {
+		diff.Branch = &StringDiff{Previous: b1, Current: b2}
+	}
+	if v1 != v2 {
+		diff.Version = &StringDiff{Previous: v1, Current: v2}
+	}
+
+	p1 := lp1.Packages()
+	p2 := lp2.Packages()
+	if !sort.StringsAreSorted(p1) {
+		p1 = make([]string, len(p1))
+		copy(p1, lp1.Packages())
+		sort.Strings(p1)
+	}
+	if !sort.StringsAreSorted(p2) {
+		p2 = make([]string, len(p2))
+		copy(p2, lp2.Packages())
+		sort.Strings(p2)
+	}
+
+	var i2next int
+	for i1 := 0; i1 < len(p1); i1++ {
+		pkg1 := p1[i1]
+
+		var matched bool
+		for i2 := i2next; i2 < len(p2); i2++ {
+			pkg2 := p2[i2]
+
+			switch strings.Compare(pkg1, pkg2) {
+			case 0: // Found matching package
+				matched = true
+				i2next = i2 + 1 // Don't evaluate to this again
+			case +1: // Found a new package
+				add := StringDiff{Current: pkg2}
+				diff.Packages = append(diff.Packages, add)
+				i2next = i2 + 1 // Don't evaluate to this again
+				continue        // Keep looking for a match
+			case -1: // Package has been removed (handled below)
+				break
+			}
+
+			break // Done evaluating this package, move onto the next
+		}
+
+		if !matched {
+			diff.Packages = append(diff.Packages, StringDiff{Previous: pkg1})
+		}
+	}
+
+	// Anything that still hasn't been evaluated are adds
+	for i2 := i2next; i2 < len(p2); i2++ {
+		pkg2 := p2[i2]
+		add := StringDiff{Current: pkg2}
+		diff.Packages = append(diff.Packages, add)
+	}
+
+	if diff.Source == nil && diff.Version == nil && diff.Revision == nil && len(diff.Packages) == 0 {
+		return nil // The projects are equivalent
+	}
+	return &diff
+}