package instructions

import (
	"strings"
	"testing"
)

func TestFormat_empty(t *testing.T) {
	tests := []struct {
		name  string
		input string
		want  string
	}{
		{"empty_string", "", ""},
		{"whitespace_only", "   ", ""},
		{"newline_only", "\n\n", ""},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			if got := Format(tt.input); got != tt.want {
				t.Errorf("Format(%q) = %q; want %q", tt.input, got, tt.want)
			}
		})
	}
}

func TestFormat_valid(t *testing.T) {
	tests := []struct {
		name  string
		input string
	}{
		{"single_line", "hello world"},
		{"multi_line", "line 1\nline 2\nline 3"},
		{"trailing_newlines", "content\n\n\n"},
		{"leading_whitespace", "\n\ncontent"},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got := Format(tt.input)
			if !strings.HasPrefix(got, "> Instructions:\n") {
				t.Errorf("missing instructions header")
			}
			if !strings.HasSuffix(got, "\n") {
				t.Errorf("does not end with newline")
			}
			lines := strings.Split(got, "\n")
			for _, line := range lines {
				if line != "" && !strings.HasPrefix(line, ">") {
					t.Errorf("line does not start with '>': %q", line)
				}
			}
		})
	}
}

func TestFileName_constant(t *testing.T) {
	if FileName != ".dirmd" {
		t.Errorf("FileName = %q; want \".dirmd\"", FileName)
	}
}