package runtime

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

	"browser.local/run/protocol"
)

const maxExecutionContentBytes = 64 * 1024

type WorkspaceResolver struct {
	root string
}

func NewWorkspaceResolver(root string) WorkspaceResolver {
	if strings.TrimSpace(root) == "" {
		root = filepath.Join(".", ".run-workspace")
	}
	return WorkspaceResolver{root: root}
}

func (resolver WorkspaceResolver) Scope(serverInstanceID string, profileKey string) (string, error) {
	if err := validateWorkspaceComponent(serverInstanceID, "serverInstanceId"); err != nil {
		return "", err
	}
	if err := validateWorkspaceComponent(profileKey, "profileKey"); err != nil {
		return "", err
	}
	root, err := filepath.Abs(resolver.root)
	if err != nil {
		return "", fmt.Errorf("resolve workspace root: %w", err)
	}
	if err := ensureDirectory(root); err != nil {
		return "", fmt.Errorf("secure workspace root: %w", err)
	}
	instances := filepath.Join(root, "instances")
	if err := ensureDirectory(instances); err != nil {
		return "", fmt.Errorf("secure workspace instances: %w", err)
	}
	serverDir := filepath.Join(instances, serverInstanceID)
	if err := ensureDirectory(serverDir); err != nil {
		return "", fmt.Errorf("secure server workspace: %w", err)
	}
	scope := filepath.Join(serverDir, profileKey)
	if err := ensureDirectory(scope); err != nil {
		return "", fmt.Errorf("secure profile workspace: %w", err)
	}
	return scope, nil
}

func (resolver WorkspaceResolver) ExistingTarget(scope string, key string) (string, error) {
	path, err := resolver.target(scope, key, false)
	if err != nil {
		return "", err
	}
	info, err := os.Lstat(path)
	if err != nil {
		return "", err
	}
	if info.Mode()&os.ModeSymlink != 0 || !info.Mode().IsRegular() {
		return "", fmt.Errorf("target must be a regular file")
	}
	return path, nil
}

func (resolver WorkspaceResolver) ExistingDirectory(scope string, key string) (string, error) {
	if strings.TrimSpace(scope) == "" || !protocol.ValidLogicalFileKey(key) || filepath.IsAbs(key) || strings.Contains(key, string(rune(92))) {
		return "", fmt.Errorf("logical directory is unsafe")
	}
	cleanScope, err := filepath.Abs(scope)
	if err != nil {
		return "", err
	}
	root, err := filepath.Abs(resolver.root)
	if err != nil {
		return "", err
	}
	rel, err := filepath.Rel(root, cleanScope)
	if err != nil || rel == "." || strings.HasPrefix(rel, "..") || filepath.IsAbs(rel) {
		return "", fmt.Errorf("workspace scope escapes root")
	}
	current := cleanScope
	for _, part := range strings.Split(filepath.ToSlash(key), "/") {
		if part == "" || part == "." || part == ".." {
			return "", fmt.Errorf("logical directory contains unsafe component")
		}
		current = filepath.Join(current, part)
		info, statErr := os.Lstat(current)
		if statErr != nil {
			return "", statErr
		}
		if info.Mode()&os.ModeSymlink != 0 || !info.IsDir() {
			return "", fmt.Errorf("logical directory is not a real directory")
		}
	}
	return current, nil
}

func (resolver WorkspaceResolver) WritableTarget(scope string, key string) (string, string, error) {
	if strings.HasPrefix(key, "actions/") || strings.HasPrefix(key, "state/") || key == "actions" || key == "state" {
		return "", "", fmt.Errorf("target is reserved")
	}
	parts := strings.Split(filepath.ToSlash(key), "/")
	parent := scope
	for _, part := range parts[:len(parts)-1] {
		parent = filepath.Join(parent, part)
		if err := ensureDirectory(parent); err != nil {
			return "", "", err
		}
	}
	path, err := resolver.target(scope, key, true)
	if err != nil {
		return "", "", err
	}
	return path, filepath.Dir(path), nil
}

func (resolver WorkspaceResolver) target(scope string, key string, allowMissingFinal bool) (string, error) {
	if strings.TrimSpace(scope) == "" {
		return "", fmt.Errorf("workspace scope is invalid")
	}
	if !protocol.ValidLogicalFileKey(key) || filepath.IsAbs(key) || strings.Contains(key, `\`) {
		return "", fmt.Errorf("logical key is unsafe")
	}
	cleanScope, err := filepath.Abs(scope)
	if err != nil {
		return "", err
	}
	root, err := filepath.Abs(resolver.root)
	if err != nil {
		return "", err
	}
	rel, err := filepath.Rel(root, cleanScope)
	if err != nil || rel == "." || strings.HasPrefix(rel, "..") || filepath.IsAbs(rel) {
		return "", fmt.Errorf("workspace scope escapes root")
	}
	parts := strings.Split(filepath.ToSlash(key), "/")
	current := cleanScope
	for index, part := range parts {
		if part == "" || part == "." || part == ".." {
			return "", fmt.Errorf("logical key contains unsafe component")
		}
		current = filepath.Join(current, part)
		info, statErr := os.Lstat(current)
		if statErr != nil {
			if allowMissingFinal && index == len(parts)-1 && os.IsNotExist(statErr) {
				return current, nil
			}
			return "", statErr
		}
		if info.Mode()&os.ModeSymlink != 0 {
			return "", fmt.Errorf("logical key contains a symlink")
		}
		if index < len(parts)-1 && !info.IsDir() {
			return "", fmt.Errorf("logical key parent is not a directory")
		}
		if index == len(parts)-1 && info.Mode()&os.ModeType != 0 {
			return "", fmt.Errorf("target is a special file")
		}
	}
	return current, nil
}

func ensureDirectory(path string) error {
	if info, err := os.Lstat(path); err == nil {
		if info.Mode()&os.ModeSymlink != 0 || !info.IsDir() {
			return fmt.Errorf("path is not a real directory")
		}
		return os.Chmod(path, 0o700)
	} else if !os.IsNotExist(err) {
		return err
	}
	parent := filepath.Dir(path)
	if parent != path {
		if err := ensureDirectory(parent); err != nil {
			return err
		}
	}
	if err := os.Mkdir(path, 0o700); err != nil && !os.IsExist(err) {
		return err
	}
	info, err := os.Lstat(path)
	if err != nil || info.Mode()&os.ModeSymlink != 0 || !info.IsDir() {
		return fmt.Errorf("created path is not a real directory")
	}
	return os.Chmod(path, 0o700)
}

func validateWorkspaceComponent(value string, field string) error {
	if strings.TrimSpace(value) == "" || value != strings.TrimSpace(value) || value == "." || value == ".." || strings.ContainsAny(value, `/\`) || !protocol.ValidLogicalFileKey(value) {
		return fmt.Errorf("%s is unsafe", field)
	}
	return nil
}