package agent

import (
	"bytes"
	"context"
	"encoding/json"
	"io"
	"net/http"

	"github.com/x-grk/longpolling-remote-access/internal/proto"
)

// runTask fetches one task, executes it, and posts the result back.
func (a *Agent) runTask(ctx context.Context, taskID string) {
	env, err := a.fetchTask(ctx, taskID)
	if err != nil {
		return
	}
	var res proto.TaskResult
	if env.Type == proto.TaskSysUpdate {
		res = a.doUpdate()
	} else {
		res = a.execTask(env)
	}
	a.postResult(ctx, taskID, res)
}

func (a *Agent) fetchTask(ctx context.Context, taskID string) (proto.TaskEnvelope, error) {
	var env proto.TaskEnvelope
	req, _ := http.NewRequestWithContext(ctx, http.MethodGet, a.cfg.Host+"/api/agent/task/"+taskID, nil)
	a.authHeaders(req)
	resp, err := a.http.Do(req)
	if err != nil {
		return env, err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return env, errStatus(resp.StatusCode)
	}
	err = json.NewDecoder(resp.Body).Decode(&env)
	return env, err
}

func (a *Agent) postResult(ctx context.Context, taskID string, res proto.TaskResult) {
	body, _ := json.Marshal(res)
	req, _ := http.NewRequestWithContext(ctx, http.MethodPost, a.cfg.Host+"/api/agent/task/"+taskID+"/result", bytes.NewReader(body))
	a.authHeaders(req)
	req.Header.Set("Content-Type", "application/json")
	resp, err := a.http.Do(req)
	if err != nil {
		return
	}
	io.Copy(io.Discard, resp.Body)
	resp.Body.Close()
}

// execTask runs a single file-manager or user-management operation natively
// and returns a result.
func (a *Agent) execTask(env proto.TaskEnvelope) proto.TaskResult {
	data, err := dispatchTask(env)
	if err != nil {
		return proto.TaskResult{Error: err.Error()}
	}
	raw, err := json.Marshal(data)
	if err != nil {
		return proto.TaskResult{Error: err.Error()}
	}
	return proto.TaskResult{OK: true, Data: raw}
}

type statusErr int

func (e statusErr) Error() string { return "server status " + itoa(int(e)) }
func errStatus(code int) error    { return statusErr(code) }

func itoa(n int) string { return itoa64(int64(n)) }

func itoa64(n int64) string {
	if n == 0 {
		return "0"
	}
	neg := n < 0
	if neg {
		n = -n
	}
	var b [24]byte
	i := len(b)
	for n > 0 {
		i--
		b[i] = byte('0' + n%10)
		n /= 10
	}
	if neg {
		i--
		b[i] = '-'
	}
	return string(b[i:])
}