package exec

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"
)

type StubBackend struct{}

func (s *StubBackend) Name() string { return "stub" }

func (s *StubBackend) Execute(ctx context.Context, req Request) (*Result, error) {
	patches := make(map[string][]byte)
	for _, target := range req.Targets {
		outPath := filepath.Join(req.WorkDir, target)
		_ = os.MkdirAll(filepath.Dir(outPath), 0o755)

		var content []byte
		if strings.HasSuffix(target, ".json") {
			// 若原文件已存在且为有效 JSON，保留其内容
			if existing, err := os.ReadFile(outPath); err == nil {
				var dummy interface{}
				if json.Unmarshal(existing, &dummy) == nil {
					content = existing
				}
			}
			if len(content) == 0 {
				content = []byte(`{"status":"mock_ok"}`)
			}
		} else {
			content = []byte(fmt.Sprintf("# 模拟生成结果\n\n- 目标文件: %s\n- 提示词摘要: %s\n", target, req.Prompt))
		}

		_ = os.WriteFile(outPath, content, 0o644)
		patches[target] = content
	}

	return &Result{
		Success: true,
		Patches: patches,
		Logs:    "Stub agent execution completed.",
	}, nil
}