package app

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

func resolveSessionConfigPathWithCandidates(flagValue string, candidates []string) (string, error) {
	if explicit := strings.TrimSpace(flagValue); explicit != "" {
		return explicit, nil
	}

	resolved, err := discoverSessionConfigPathWithCandidates(candidates)
	if err != nil {
		return "", err
	}
	if resolved.Path != "" {
		return resolved.Path, nil
	}
	return "", missingSessionConfigError(resolved.Searched, "")
}

type sessionConfigDiscovery struct {
	Path     string
	Searched []string
}

func discoverSessionConfigPathWithCandidates(candidates []string) (sessionConfigDiscovery, error) {
	ordered := make([]string, 0, len(candidates))
	for _, raw := range candidates {
		path := strings.TrimSpace(raw)
		if path == "" {
			continue
		}
		ordered = append(ordered, path)
		info, err := os.Stat(path)
		if err == nil {
			if info.IsDir() {
				continue
			}
			return sessionConfigDiscovery{Path: filepath.Clean(path), Searched: ordered}, nil
		}
		if errors.Is(err, os.ErrNotExist) {
			continue
		}
		return sessionConfigDiscovery{}, fmt.Errorf("check default session config %q: %w", path, err)
	}

	return sessionConfigDiscovery{Searched: ordered}, nil
}

func missingSessionConfigError(searched []string, remoteDetail string) error {
	ordered := append([]string(nil), searched...)
	if len(ordered) == 0 {
		if strings.TrimSpace(remoteDetail) != "" {
			return fmt.Errorf("no session config path provided and no default locations configured; %s", remoteDetail)
		}
		return fmt.Errorf("no session config path provided and no default locations configured")
	}
	msg := fmt.Sprintf(
		"no session config path provided and no default session config found; searched: %s",
		strings.Join(ordered, ", "),
	)
	if strings.TrimSpace(remoteDetail) != "" {
		msg += "; " + strings.TrimSpace(remoteDetail)
	}
	msg += "; pass --session to use an explicit path"
	return fmt.Errorf("%s", msg)
}