package agent

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

	"chat-agent-system/internal/config"
	"chat-agent-system/internal/workspace"
)

type CursorCLIBackend struct {
	cfg *config.Config
}

func (c *CursorCLIBackend) Name() string { return "cursor-cli" }

func (c *CursorCLIBackend) Execute(ctx context.Context, req Request) (*Result, error) {
	if len(req.Targets) == 0 {
		req.Targets = []string{workspace.DeliverableKey}
	}

	workDir := req.WorkDir
	if !filepath.IsAbs(workDir) {
		wd, _ := os.Getwd()
		workDir = filepath.Join(wd, workDir)
	}

	payload, _ := json.Marshal(map[string]any{
		"workspace":    workDir,
		"api_key":      c.cfg.CursorAPIKey,
		"model":        c.cfg.CursorModel,
		"prompt":       req.Prompt,
		"instructions": req.Instructions,
		"targets":      req.Targets,
	})

	bridgeBin := c.cfg.CursorBridgeBin
	if !filepath.IsAbs(bridgeBin) {
		wd, _ := os.Getwd()
		bridgeBin = filepath.Join(wd, bridgeBin)
	}

	timeout := req.Timeout
	if timeout <= 0 {
		timeout = c.cfg.AgentTimeout
	}
	runCtx, cancel := context.WithTimeout(ctx, timeout)
	defer cancel()

	cmd := exec.CommandContext(runCtx, bridgeBin)
	cmd.Dir = workDir
	cmd.Stdin = bytes.NewReader(payload)
	cmd.Env = append(os.Environ(),
		"CURSOR_API_KEY="+c.cfg.CursorAPIKey,
		"CURSOR_MODEL="+c.cfg.CursorModel,
	)

	var stdout, stderr bytes.Buffer
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr

	err := cmd.Run()
	if err != nil {
		return &Result{
			Success:     false,
			ErrorReason: fmt.Sprintf("cursor execution error: %v, stderr: %s", err, stderr.String()),
		}, nil
	}

	type bridgeResponse struct {
		OK             bool   `json:"ok"`
		FallbackReason string `json:"fallback_reason"`
		Stderr         string `json:"stderr"`
	}
	var bResp bridgeResponse
	lines := strings.Split(strings.TrimSpace(stdout.String()), "\n")
	if len(lines) > 0 {
		_ = json.Unmarshal([]byte(lines[len(lines)-1]), &bResp)
	}

	if !bResp.OK {
		errMsg := bResp.FallbackReason
		if bResp.Stderr != "" {
			errMsg += " (" + bResp.Stderr + ")"
		}
		if errMsg == "" {
			errMsg = "cursor bridge reported task failed"
		}
		return &Result{
			Success:     false,
			ErrorReason: errMsg,
			Logs:        stdout.String(),
		}, nil
	}

	patches := make(map[string][]byte)
	for _, t := range req.Targets {
		p := filepath.Join(workDir, t)
		if b, err := os.ReadFile(p); err == nil {
			patches[t] = b
		}
	}

	return &Result{
		Success: true,
		Patches: patches,
		Logs:    stdout.String(),
	}, nil
}