package veraetime

import (
	"bufio"
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"strings"
	"time"
)

// DefaultBaseURL is the production VeraeTime API.
const DefaultBaseURL = "https://api.veraetime.net"

// TokenRefreshSkew is how far before expires_at a host token is refreshed.
const TokenRefreshSkew = 60 * time.Second

var expiryRe = regexp.MustCompile(`^(.*T\d{2}:\d{2}:\d{2})(\.\d+)?([+-]\d{2}:\d{2}|Z)?$`)

// DefaultAuthPath returns VERAE_AUTH_PROPERTIES or $HOME/.verae/auth.properties.
func DefaultAuthPath() string {
	if v := strings.TrimSpace(os.Getenv("VERAE_AUTH_PROPERTIES")); v != "" {
		return v
	}
	home, err := os.UserHomeDir()
	if err != nil || home == "" {
		return filepath.Join(".verae", "auth.properties")
	}
	return filepath.Join(home, ".verae", "auth.properties")
}

// ReadProperties loads key=value lines from path. Missing file yields empty map.
func ReadProperties(path string) (map[string]string, error) {
	f, err := os.Open(path)
	if err != nil {
		if os.IsNotExist(err) {
			return map[string]string{}, nil
		}
		return nil, err
	}
	defer f.Close()
	props := make(map[string]string)
	sc := bufio.NewScanner(f)
	for sc.Scan() {
		line := strings.TrimSpace(sc.Text())
		if line == "" || strings.HasPrefix(line, "#") || !strings.Contains(line, "=") {
			continue
		}
		key, val, _ := strings.Cut(line, "=")
		props[strings.TrimSpace(key)] = strings.TrimSpace(val)
	}
	return props, sc.Err()
}

// WriteProperties merges props into path (mode 0600); parent dir 0700.
func WriteProperties(path string, props map[string]string) error {
	if err := os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
		return err
	}
	merged, err := ReadProperties(path)
	if err != nil {
		return err
	}
	for k, v := range props {
		merged[k] = v
	}
	tmp := path + ".tmp"
	f, err := os.OpenFile(tmp, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0o600)
	if err != nil {
		return err
	}
	for k, v := range merged {
		if _, err := fmt.Fprintf(f, "%s=%s\n", k, v); err != nil {
			f.Close()
			_ = os.Remove(tmp)
			return err
		}
	}
	if err := f.Close(); err != nil {
		_ = os.Remove(tmp)
		return err
	}
	_ = os.Chmod(tmp, 0o600)
	if err := os.Rename(tmp, path); err != nil {
		_ = os.Remove(tmp)
		return err
	}
	_ = os.Chmod(path, 0o600)
	return nil
}

// ParseExpiry parses VeraeTime expiresAt / expires_at strings.
func ParseExpiry(value string) (time.Time, bool) {
	text := strings.TrimSpace(value)
	if text == "" {
		return time.Time{}, false
	}
	if strings.HasSuffix(text, "Z") {
		text = text[:len(text)-1] + "+00:00"
	}
	m := expiryRe.FindStringSubmatch(text)
	if m == nil {
		t, err := time.Parse(time.RFC3339, strings.TrimSpace(value))
		if err != nil {
			return time.Time{}, false
		}
		return t.UTC(), true
	}
	frac := m[2]
	if frac != "" {
		if len(frac) > 7 {
			frac = frac[:7]
		}
	}
	zone := m[3]
	if zone == "" || zone == "Z" {
		zone = "+00:00"
	}
	parsed, err := time.Parse("2006-01-02T15:04:05.999999-07:00", m[1]+frac+zone)
	if err != nil {
		parsed, err = time.Parse("2006-01-02T15:04:05-07:00", m[1]+zone)
		if err != nil {
			return time.Time{}, false
		}
	}
	return parsed.UTC(), true
}

func storedAccessToken(props map[string]string) string {
	for _, k := range []string{"access_token", "id_token", "auth_token"} {
		if v := strings.TrimSpace(props[k]); v != "" {
			return v
		}
	}
	return ""
}