package template

import (
	"errors"
	"strings"
	"testing"
)

func TestTemplateError(t *testing.T) {
	cause := errors.New("boom")
	tests := []struct {
		name  string
		err   *TemplateError
		phase string
	}{
		{"load", NewTemplateLoadError("cannot read", cause), "load"},
		{"parse", NewTemplateParseError("bad syntax", cause), "parse"},
		{"execute", NewTemplateExecuteError("failed render", cause), "execute"},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			if tt.err.Phase != tt.phase {
				t.Errorf("phase = %q", tt.err.Phase)
			}
			msg := tt.err.Error()
			if !strings.Contains(msg, "template "+tt.phase+" error") || !strings.Contains(msg, "boom") {
				t.Errorf("message = %q", msg)
			}
			if !errors.Is(tt.err, cause) {
				t.Error("errors.Is must reach cause")
			}
			var te *TemplateError
			if !errors.As(error(tt.err), &te) || te != tt.err {
				t.Error("errors.As failed")
			}
		})
	}
}

func TestTemplateErrorWithoutCause(t *testing.T) {
	e := NewTemplateParseError("only message", nil)
	if got := e.Error(); got != "template parse error: only message" {
		t.Errorf("got %q", got)
	}
	if e.Unwrap() != nil {
		t.Error("Unwrap must be nil")
	}
}