// Copyright 2017, The Go Authors. All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE.md file.

package cmp

// defaultReporter implements the reporter interface.

//

// As Equal serially calls the PushStep, Report, and PopStep methods, the

// defaultReporter constructs a tree-based representation of the compared value

// and the result of each comparison (see valueNode).

//

// When the String method is called, the FormatDiff method transforms the

// valueNode tree into a textNode tree, which is a tree-based representation

// of the textual output (see textNode).

//

// Lastly, the textNode.String method produces the final report as a string.

type defaultReporter struct {

	root *valueNode

	curr *valueNode

}

func (r *defaultReporter) PushStep(ps PathStep) {

	r.curr = r.curr.PushStep(ps)

	if r.root == nil {

		r.root = r.curr

	}

}

func (r *defaultReporter) Report(rs Result) {

	r.curr.Report(rs)

}

func (r *defaultReporter) PopStep() {

	r.curr = r.curr.PopStep()

}

// String provides a full report of the differences detected as a structured

// literal in pseudo-Go syntax. String may only be called after the entire tree

// has been traversed.

func (r *defaultReporter) String() string {

	assert(r.root != nil && r.curr == nil)

	if r.root.NumDiff == 0 {

		return ""

	}

	return formatOptions{}.FormatDiff(r.root).String()

}

func assert(ok bool) {

	if !ok {

		panic("assertion failure")

	}

}