package host

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net"
	"net/http"
	"time"

	execlease "github.com/carlosframework/platform/internal/hostexec"
)

func (h ClaimRootHTTP) serveExecution(w http.ResponseWriter, r *http.Request, peer StopPeer) {
	var q execlease.ExecutionRequest
	dec := json.NewDecoder(http.MaxBytesReader(w, r.Body, 16<<10))
	dec.DisallowUnknownFields()
	if dec.Decode(&q) != nil || dec.Decode(new(any)) != io.EOF {
		w.WriteHeader(http.StatusBadRequest)
		return
	}
	if h.Execution == nil {
		w.WriteHeader(http.StatusServiceUnavailable)
		return
	}
	out, err := h.Execution.Execute(r.Context(), execlease.ControllerProcess{KernelBootID: peer.BootID, PID: peer.PID, Start: peer.ProcessStart}, q)
	if errors.Is(err, errReinstallRetired) {
		w.WriteHeader(http.StatusGone)
		return
	}
	if err != nil {
		w.WriteHeader(http.StatusConflict)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	_ = json.NewEncoder(w).Encode(out)
}

func rootExecutionClient(path string) func(context.Context, execlease.ExecutionRequest) (execlease.ExecutionResponse, error) {
	return func(ctx context.Context, q execlease.ExecutionRequest) (execlease.ExecutionResponse, error) {
		var out execlease.ExecutionResponse
		raw, err := json.Marshal(q)
		if err != nil {
			return out, err
		}
		ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
		defer cancel()
		tr := &http.Transport{DisableKeepAlives: true, DialContext: func(ctx context.Context, _, _ string) (net.Conn, error) {
			return (&net.Dialer{}).DialContext(ctx, "unix", path)
		}}
		defer tr.CloseIdleConnections()
		for attempt := 0; attempt < 2; attempt++ {
			req, e := http.NewRequestWithContext(ctx, http.MethodPost, "http://control/claim/execution", bytes.NewReader(raw))
			if e != nil {
				return out, e
			}
			resp, e := (&http.Client{Transport: tr}).Do(req)
			if e != nil {
				err = e
				continue
			}
			if resp.StatusCode == http.StatusGone {
				resp.Body.Close()
				return out, fmt.Errorf("%s: %w", q.Host, errReinstallRetired)
			}
			if resp.StatusCode != http.StatusOK {
				resp.Body.Close()
				return out, execlease.ErrLost
			}
			limited := &io.LimitedReader{R: resp.Body, N: (16 << 10) + 1}
			dec := json.NewDecoder(limited)
			dec.DisallowUnknownFields()
			err = dec.Decode(&out)
			if err == nil && (dec.Decode(new(any)) != io.EOF || limited.N == 0) {
				err = execlease.ErrState
			}
			resp.Body.Close()
			if err != nil {
				continue
			}
			serving := q.Operation == "executionView" && q.Token == "" && out.Status == "serving" && out.Token == "" && out.SafeUntil == 0 && out.LeaseETag == "" && out.Expires.IsZero()
			if q.Operation == "executionView" && q.Token == "" && !serving {
				return execlease.ExecutionResponse{}, execlease.ErrState
			}
			if out.Schema != 1 || out.Host != q.Host || out.Incarnation != q.Incarnation || out.Stamp != q.Stamp || out.Session != q.Session || out.Op != q.Op || (!serving && out.Token == "") || out.BootID == "" {
				return execlease.ExecutionResponse{}, execlease.ErrState
			}
			return out, nil
		}
		return out, err
	}
}