package workspace

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

	"github.com/jackc/pgx/v5/pgxpool"
)

var (
	ErrPathEscape      = errors.New("workspace: path escapes data root")
	ErrWorkDirNotFound = errors.New("workspace: work directory not found")
)

// Resolver 将逻辑 ID 解析为受约束的工作区路径。
type Resolver struct {
	dataRoot string
	pool     *pgxpool.Pool
}

func NewResolver(dataRoot string, pool *pgxpool.Pool) *Resolver {
	return &Resolver{dataRoot: dataRoot, pool: pool}
}

// EnsureUnderDataRoot 校验绝对路径位于 dataRoot 内。
func (r *Resolver) EnsureUnderDataRoot(path string) (string, error) {
	if strings.TrimSpace(path) == "" {
		return "", fmt.Errorf("workspace: empty path")
	}
	abs, err := filepath.Abs(path)
	if err != nil {
		return "", err
	}
	root, err := filepath.Abs(r.dataRoot)
	if err != nil {
		return "", err
	}
	rel, err := filepath.Rel(root, abs)
	if err != nil {
		return "", ErrPathEscape
	}
	if rel == ".." || strings.HasPrefix(rel, ".."+string(os.PathSeparator)) {
		return "", ErrPathEscape
	}
	return abs, nil
}

// ResolveDocWorkDir 从 document_records 读取 work_dir 并沙箱校验。
func (r *Resolver) ResolveDocWorkDir(ctx context.Context, docID string) (string, error) {
	docID = strings.TrimSpace(docID)
	if docID == "" {
		return "", fmt.Errorf("workspace: doc_id required")
	}
	if r.pool == nil {
		return "", ErrWorkDirNotFound
	}
	var workDir string
	err := r.pool.QueryRow(ctx, `
		SELECT COALESCE(work_dir, '')
		FROM document_records
		WHERE doc_id = $1
	`, docID).Scan(&workDir)
	if err != nil || strings.TrimSpace(workDir) == "" {
		return "", ErrWorkDirNotFound
	}
	return r.EnsureUnderDataRoot(workDir)
}

// ResolveStoredWorkDir 沙箱校验已持久化的工作区路径（如 task run workspace_id）。
func (r *Resolver) ResolveStoredWorkDir(storedPath string) (string, error) {
	storedPath = strings.TrimSpace(storedPath)
	if storedPath == "" {
		return "", ErrWorkDirNotFound
	}
	return r.EnsureUnderDataRoot(storedPath)
}