package config

import (
	"os"
	"path/filepath"
	"testing"
)

type testConfig struct {
	Host string `yaml:"host" env:"HOST"`
	Port int    `yaml:"port" env:"PORT"`
	TLS  bool   `yaml:"tls"  env:"TLS"`
	Tags []string `yaml:"tags" env:"TAGS"`
}

func TestLoadYAML_Basic(t *testing.T) {
	dir := t.TempDir()
	path := filepath.Join(dir, "test.yml")
	content := `
host: myhost
port: 9000
tls: true
tags:
  - a
  - b
`
	if err := os.WriteFile(path, []byte(content), 0600); err != nil {
		t.Fatal(err)
	}

	cfg, err := LoadYAML[testConfig](path, false)
	if err != nil {
		t.Fatalf("LoadYAML error: %v", err)
	}
	if cfg.Host != "myhost" {
		t.Errorf("Host = %q, want %q", cfg.Host, "myhost")
	}
	if cfg.Port != 9000 {
		t.Errorf("Port = %d, want 9000", cfg.Port)
	}
	if !cfg.TLS {
		t.Error("TLS should be true")
	}
	if len(cfg.Tags) != 2 {
		t.Errorf("Tags len = %d, want 2", len(cfg.Tags))
	}
}

func TestLoadYAML_Optional_MissingFile(t *testing.T) {
	cfg, err := LoadYAML[testConfig]("/nonexistent/path.yml", true)
	if err != nil {
		t.Fatalf("optional missing file should not error: %v", err)
	}
	if cfg.Host != "" {
		t.Errorf("zero value expected, got host=%q", cfg.Host)
	}
}

func TestLoadYAML_Required_MissingFile(t *testing.T) {
	_, err := LoadYAML[testConfig]("/nonexistent/path.yml", false)
	if err == nil {
		t.Error("expected error for missing required file")
	}
}

func TestLoadYAML_EmptyPath_Optional(t *testing.T) {
	cfg, err := LoadYAML[testConfig]("", true)
	if err != nil {
		t.Fatalf("empty optional path should not error: %v", err)
	}
	_ = cfg
}

func TestOverrideFromEnv_String(t *testing.T) {
	t.Setenv("HOST", "envhost")
	cfg := testConfig{Host: "original"}
	if err := OverrideFromEnv(&cfg, ""); err != nil {
		t.Fatal(err)
	}
	if cfg.Host != "envhost" {
		t.Errorf("Host = %q, want envhost", cfg.Host)
	}
}

func TestOverrideFromEnv_Int(t *testing.T) {
	t.Setenv("PORT", "8080")
	cfg := testConfig{Port: 1234}
	if err := OverrideFromEnv(&cfg, ""); err != nil {
		t.Fatal(err)
	}
	if cfg.Port != 8080 {
		t.Errorf("Port = %d, want 8080", cfg.Port)
	}
}

func TestOverrideFromEnv_Bool(t *testing.T) {
	t.Setenv("TLS", "false")
	cfg := testConfig{TLS: true}
	if err := OverrideFromEnv(&cfg, ""); err != nil {
		t.Fatal(err)
	}
	if cfg.TLS {
		t.Error("TLS should be false after env override")
	}
}

func TestOverrideFromEnv_Slice(t *testing.T) {
	t.Setenv("TAGS", "x,y,z")
	cfg := testConfig{}
	if err := OverrideFromEnv(&cfg, ""); err != nil {
		t.Fatal(err)
	}
	if len(cfg.Tags) != 3 || cfg.Tags[0] != "x" {
		t.Errorf("Tags = %v, want [x y z]", cfg.Tags)
	}
}

func TestOverrideFromEnv_WithPrefix(t *testing.T) {
	t.Setenv("APP_HOST", "prefixed")
	cfg := testConfig{Host: "original"}
	if err := OverrideFromEnv(&cfg, "APP"); err != nil {
		t.Fatal(err)
	}
	if cfg.Host != "prefixed" {
		t.Errorf("Host = %q, want prefixed", cfg.Host)
	}
}

func TestOverrideFromEnv_NoEnvSet_NoChange(t *testing.T) {
	os.Unsetenv("HOST")
	os.Unsetenv("PORT")
	cfg := testConfig{Host: "keep", Port: 42}
	if err := OverrideFromEnv(&cfg, ""); err != nil {
		t.Fatal(err)
	}
	if cfg.Host != "keep" || cfg.Port != 42 {
		t.Errorf("unset env should not change values: host=%q port=%d", cfg.Host, cfg.Port)
	}
}