package agents

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"log/slog"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"

	"g.fc.run/misc/byre/internal/api"
	"g.fc.run/misc/byre/internal/mcp"
	"g.fc.run/misc/byre/internal/store"
)

const (
	bundleTimeout = 5 * time.Minute
	MaxRunOutput  = 64 << 10
)

type runOnClientArgs struct {
	Paths   []string `json:"paths"`
	Command string   `json:"command"`
	Why     string   `json:"why"`
}

func (m *Manager) runOnClientTool(l *live) mcp.Tool {
	return mcp.Tool{
		Name: "run_on_client",
		Description: "Ask the human to run a command on their own Mac, with files from your worktree, for example to install and launch an app you built. " +
			"byre packs paths into a bundle now, so later changes to them aren't sent, and files a card in the human's inbox showing why, the command and the files. " +
			"Every Mac the human has byre open on shows the card with Run and Dismiss; each Mac where they click Run downloads the bundle, unpacks it into a new empty directory, " +
			"and runs command there with zsh as a login shell, as the human. The directory is deleted once the command finishes, so copy anything that must stay elsewhere first. " +
			"The command keeps running if it quits byre's app, and the app reports it when it next starts. " +
			"This call returns at once; you don't need to end your turn. Each Mac's run reaches you as a message with its host name, exit status and the last 64 KiB of its output. " +
			"The card stays until the human dismisses it, so it can be run again or on another Mac.",
		InputSchema: json.RawMessage(`{
			"type": "object",
			"properties": {
				"paths": {"type": "array", "items": {"type": "string"}, "description": "Files or directories to send, relative to your worktree; each is unpacked at the same relative path. May be empty."},
				"command": {"type": "string", "description": "The zsh command to run in the directory the bundle unpacks into, e.g. 'rm -rf ~/Applications/byre.app && ditto mac/.build/byre.app ~/Applications/byre.app && (pkill -x Byre; open ~/Applications/byre.app)'."},
				"why": {"type": "string", "description": "One or two sentences for the human: what running it does and why."}
			},
			"required": ["paths", "command", "why"]
		}`),
		Handler: func(ctx context.Context, raw json.RawMessage) (string, error) {
			return m.runOnClient(ctx, l, raw)
		},
	}
}

func (m *Manager) runOnClient(ctx context.Context, l *live, raw json.RawMessage) (string, error) {
	args := runOnClientArgs{}
	err := json.Unmarshal(raw, &args)
	if err != nil {
		return "", fmt.Errorf("malformed run_on_client call: %w", err)
	}
	if strings.TrimSpace(args.Command) == "" {
		return "", errors.New("command is empty")
	}
	if strings.TrimSpace(args.Why) == "" {
		return "", errors.New("why is empty: say what running it does and why")
	}

	paths, err := checkBundlePaths(l.dir, args.Paths)
	if err != nil {
		return "", err
	}

	id := store.NewID()
	size, err := m.writeBundle(ctx, l.dir, paths, m.store.BundlePath(id))
	if err != nil {
		return "", err
	}

	payload := map[string]any{
		"why":     args.Why,
		"command": args.Command,
		"paths":   paths,
		"bytes":   size,
	}
	err = m.store.CreateInboxItem(ctx, m.newItem(l, id, id, api.ClientRun, payload))
	if err != nil {
		os.Remove(m.store.BundlePath(id))
		return "", err
	}
	return fmt.Sprintf("Run request %s filed in the human's inbox with a %d-byte bundle. Each Mac's run will reach you as a message.", id, size), nil
}

func checkBundlePaths(dir string, paths []string) ([]string, error) {
	root, err := os.OpenRoot(dir)
	if err != nil {
		return nil, err
	}
	defer root.Close()

	out := []string{}
	for _, p := range paths {
		clean := filepath.Clean(p)
		if filepath.IsAbs(clean) || clean == "." || strings.HasPrefix(clean, "-") {
			return nil, fmt.Errorf("path %q must be relative to your worktree and inside it", p)
		}
		_, err = root.Lstat(clean)
		if err != nil {
			return nil, fmt.Errorf("path %q: %w", p, err)
		}
		out = append(out, clean)
	}
	return out, nil
}

func (m *Manager) writeBundle(ctx context.Context, dir string, paths []string, dest string) (int64, error) {
	err := os.MkdirAll(filepath.Dir(dest), 0o755)
	if err != nil {
		return 0, err
	}
	tmp := dest + ".tmp"

	cctx, cancel := context.WithTimeout(ctx, bundleTimeout)
	defer cancel()
	// -T /dev/null lets tar write an empty archive when paths is empty.
	cmd := exec.CommandContext(cctx, "tar", append([]string{"-czf", tmp, "-C", dir, "-T", "/dev/null", "--"}, paths...)...)
	out, err := cmd.CombinedOutput()
	if err != nil {
		os.Remove(tmp)
		return 0, fmt.Errorf("pack bundle: %w: %s", err, out)
	}

	err = os.Rename(tmp, dest)
	if err != nil {
		return 0, err
	}
	info, err := os.Stat(dest)
	if err != nil {
		return 0, err
	}
	return info.Size(), nil
}

func (m *Manager) ReportRun(ctx context.Context, user, itemID string, report api.RunReport) (api.InboxItem, error) {
	item, err := m.store.GetInboxItem(ctx, itemID)
	if err != nil {
		return item, err
	}
	if item.Kind != api.ClientRun {
		return item, fmt.Errorf("%w: item %s is a %s, not a client_run", ErrInvalid, itemID, item.Kind)
	}
	client := strings.TrimSpace(report.Client)
	if client == "" {
		return item, fmt.Errorf("%w: client is empty", ErrInvalid)
	}
	if strings.TrimSpace(report.RunId) == "" {
		return item, fmt.Errorf("%w: run_id is empty", ErrInvalid)
	}

	output := report.Output
	if len(output) > MaxRunOutput {
		output = strings.ToValidUTF8(output[len(output)-MaxRunOutput:], "")
	}
	resp := api.InboxResponse{
		Id:        report.RunId,
		ItemId:    itemID,
		User:      user,
		Type:      api.Run,
		Text:      &output,
		Client:    &client,
		ExitCode:  &report.ExitCode,
		CreatedAt: time.Now().UTC(),
	}
	added, err := m.store.AddRunResponse(ctx, resp)
	if err != nil {
		return item, err
	}
	if !added {
		slog.Info("client run already reported", "item", itemID, "response", resp.Id, "client", client)
		return m.store.GetInboxItem(ctx, itemID)
	}
	slog.Info("client run reported", "item", itemID, "response", resp.Id, "user", user, "client", client, "exit", report.ExitCode)

	go func() {
		err := m.Deliver(context.Background(), item.AgentSessionId)
		if err != nil {
			slog.Error("deliver run report", "session", item.AgentSessionId, "err", err)
		}
	}()
	return m.store.GetInboxItem(ctx, itemID)
}