package engine

import (
	"bytes"
	"errors"
	"io"
	"strings"
	"testing"
)

func TestDiagnosticsAreCanonicalAndDetached(t *testing.T) {
	t.Parallel()

	diagnostics := []Diagnostic{
		{
			Code:     "decode.type",
			Severity: SeverityError,
			Path:     Keys("later"),
			Message:  "later",
			Primary:  &Location{SourceID: "source-10", Line: 1, Column: 1},
		},
		{
			Code:     "schema.invalid",
			Severity: SeverityError,
			Path:     Keys("root"),
			Message:  "source-less",
		},
		{
			Code:     "decode.type",
			Severity: SeverityError,
			Path:     Keys("earlier"),
			Message:  "earlier",
			Primary:  &Location{SourceID: "source-2", Line: 3, Column: 4},
			Related: []Location{
				{SourceID: "source-10", Line: 1, Column: 1},
				{SourceID: "source-2", Line: 9, Column: 1},
			},
		},
	}

	var forward bytes.Buffer
	if err := WriteDiagnostics(&forward, diagnostics); err != nil {
		t.Fatal(err)
	}
	reversed := []Diagnostic{diagnostics[2], diagnostics[1], diagnostics[0]}
	var backward bytes.Buffer
	if err := WriteDiagnostics(&backward, reversed); err != nil {
		t.Fatal(err)
	}
	if forward.String() != backward.String() {
		t.Fatalf("rendering depends on submission order:\n%s\n---\n%s", forward.String(), backward.String())
	}
	lines := strings.Split(forward.String(), "\n")
	if !strings.Contains(lines[0], "source-less") || !strings.Contains(lines[1], "source-2:3:4") {
		t.Fatalf("unexpected canonical order:\n%s", forward.String())
	}
	if !strings.Contains(lines[2], "source-2:9:1") || !strings.Contains(lines[3], "source-10:1:1") {
		t.Fatalf("related locations not canonical:\n%s", forward.String())
	}

	accumulator := diagnosticAccumulator{
		sources: []SourceInfo{{
			ID:           "source-1",
			Label:        "config.yml",
			ImportedFrom: &Location{SourceID: "source-0", Line: 1},
		}},
	}
	accumulator.add(diagnostics...)
	loadErr := accumulator.loadError()
	var found *LoadError
	if !errors.As(error(loadErr), &found) || found != loadErr {
		t.Fatal("errors.As did not find LoadError")
	}

	first := loadErr.Diagnostics()
	first[1].Primary.SourceID = "mutated"
	first[1].Path.segments[0].key = "mutated"
	first[1].Related[0].SourceID = "mutated"
	second := loadErr.Diagnostics()
	if second[1].Primary.SourceID != "source-2" || second[1].Path.String() != "/earlier" || second[1].Related[0].SourceID != "source-2" {
		t.Fatal("Diagnostics returned aliased records")
	}
	sources := loadErr.Sources()
	sources[0].ImportedFrom.SourceID = "mutated"
	if loadErr.Sources()[0].ImportedFrom.SourceID != "source-0" {
		t.Fatal("Sources returned aliased records")
	}
	if got := loadErr.Error(); got != "configkit: configuration load failed with 3 errors" {
		t.Fatalf("Error() = %q", got)
	}
}

func TestWriteDiagnosticsEscapesControls(t *testing.T) {
	t.Parallel()

	diagnostic := Diagnostic{
		Code:     "validate.error",
		Severity: SeverityError,
		Path:     Keys("line\nbreak"),
		Message:  "message\r\nnext",
		Primary:  &Location{SourceID: "source\tlabel", Line: 1},
	}
	var output bytes.Buffer
	if err := WriteDiagnostics(&output, []Diagnostic{diagnostic}); err != nil {
		t.Fatal(err)
	}
	got := output.String()
	if strings.Count(got, "\n") != 1 {
		t.Fatalf("control characters created output lines: %q", got)
	}
	for _, escaped := range []string{`line\nbreak`, `message\r\nnext`, `source\tlabel`} {
		if !strings.Contains(got, escaped) {
			t.Errorf("output %q does not contain %q", got, escaped)
		}
	}
}

func TestWriteDiagnosticsPropagatesWriterFailures(t *testing.T) {
	t.Parallel()

	diagnostics := []Diagnostic{{Severity: SeverityError, Message: "safe"}}
	want := errors.New("write failed")
	if err := WriteDiagnostics(errorWriter{err: want}, diagnostics); !errors.Is(err, want) {
		t.Fatalf("error writer returned %v", err)
	}
	if err := WriteDiagnostics(shortWriter{}, diagnostics); !errors.Is(err, io.ErrShortWrite) {
		t.Fatalf("short writer returned %v", err)
	}
}

type errorWriter struct {
	err error
}

func (w errorWriter) Write(p []byte) (int, error) {
	return min(3, len(p)), w.err
}

type shortWriter struct{}

func (shortWriter) Write(p []byte) (int, error) {
	return max(0, len(p)-1), nil
}