package runtimews

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

const envWorkspaceDir = "AGENT_WORKSPACE_DIR"

func PrepareFromEnv() (string, error) {
	workspaceDir := strings.TrimSpace(os.Getenv(envWorkspaceDir))
	if workspaceDir == "" {
		workspaceDir = filepath.Join(".", "workspace", "agent_runtime")
	}
	absWorkspace, err := filepath.Abs(workspaceDir)
	if err != nil {
		return "", err
	}
	if err := os.MkdirAll(absWorkspace, 0o755); err != nil {
		return "", err
	}

	if err := seedRuntimeWorkspace(absWorkspace); err != nil {
		return "", err
	}

	if err := os.Setenv(envWorkspaceDir, absWorkspace); err != nil {
		return "", err
	}
	_ = os.Setenv("CONFIG_ENV_FILE", filepath.Join(absWorkspace, "configs", "env"))
	return absWorkspace, nil
}

func seedRuntimeWorkspace(workspaceRoot string) error {
	seedDirs := []string{"configs", "data", "bot_context", "skills"}
	for _, name := range seedDirs {
		src := filepath.Join(".", name)
		dst := filepath.Join(workspaceRoot, name)
		if err := copyDirIfMissing(src, dst); err != nil {
			return fmt.Errorf("seed %s failed: %w", name, err)
		}
	}
	if err := os.MkdirAll(filepath.Join(workspaceRoot, "workspace"), 0o755); err != nil {
		return err
	}
	return nil
}

func copyDirIfMissing(src, dst string) error {
	info, err := os.Stat(src)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return err
	}
	if !info.IsDir() {
		return nil
	}
	if err := os.MkdirAll(dst, 0o755); err != nil {
		return err
	}

	return filepath.WalkDir(src, func(path string, d os.DirEntry, walkErr error) error {
		if walkErr != nil {
			return walkErr
		}
		rel, err := filepath.Rel(src, path)
		if err != nil {
			return err
		}
		target := filepath.Join(dst, rel)
		if d.IsDir() {
			return os.MkdirAll(target, 0o755)
		}
		if _, err := os.Stat(target); err == nil {
			return nil
		}
		if err := copyFile(path, target); err != nil {
			return err
		}
		return nil
	})
}

func copyFile(src, dst string) error {
	in, err := os.Open(src)
	if err != nil {
		return err
	}
	defer in.Close()

	if err := os.MkdirAll(filepath.Dir(dst), 0o755); err != nil {
		return err
	}
	out, err := os.Create(dst)
	if err != nil {
		return err
	}
	defer out.Close()

	if _, err := io.Copy(out, in); err != nil {
		return err
	}
	return out.Sync()
}