package main

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"strings"
	"sync"
	"time"

	"git.cin.su/m/Assistant/contracts/capability"
	fleetdomain "git.cin.su/m/Assistant/modules/capability/domain"
)

type fleetEndpoint struct {
	ProviderID string
	ModelID    string
	Tier       capability.FleetTier
	URL        string
	Headers    map[string]string
	Client     *http.Client
	Timeout    time.Duration
}

type fleetStatusResponse struct {
	Readiness capability.FleetReadiness `json:"readiness"`
	Preferred capability.FleetTier      `json:"preferred_tier"`
	Selected  capability.FleetTier      `json:"selected_tier,omitempty"`
	Error     string                    `json:"error,omitempty"`
}

func fleetReadinessHandler(client *http.Client, preferred capability.FleetTier, endpoints []fleetEndpoint) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		members := make([]capability.FleetMember, 0, len(endpoints))
		members = make([]capability.FleetMember, len(endpoints))
		var waitGroup sync.WaitGroup
		for index, endpoint := range endpoints {
			waitGroup.Add(1)
			go func(index int, endpoint fleetEndpoint) {
				defer waitGroup.Done()
				members[index] = probeFleetEndpoint(r.Context(), client, endpoint)
			}(index, endpoint)
		}
		waitGroup.Wait()
		readiness, err := fleetdomain.BuildFleetReadiness(time.Now().UnixMilli(), members)
		response := fleetStatusResponse{Readiness: readiness, Preferred: preferred}
		if err == nil {
			response.Selected, err = fleetdomain.SelectFleetTier(readiness, preferred)
		}
		if err != nil {
			response.Error = err.Error()
		}
		w.Header().Set("Content-Type", "application/json")
		if response.Selected == "" {
			w.WriteHeader(http.StatusServiceUnavailable)
		}
		_ = json.NewEncoder(w).Encode(response)
	})
}

func probeFleetEndpoint(parent context.Context, fallbackClient *http.Client, endpoint fleetEndpoint) capability.FleetMember {
	member := capability.FleetMember{ProviderInstanceID: capability.ProviderInstanceID(endpoint.ProviderID), ModelDescriptorID: capability.ModelDescriptorID(endpoint.ModelID), Tier: endpoint.Tier, Reason: "NOT_CONFIGURED"}
	if strings.TrimSpace(endpoint.URL) == "" {
		return member
	}
	timeout := endpoint.Timeout
	if timeout <= 0 {
		timeout = 2 * time.Second
	}
	ctx, cancel := context.WithTimeout(parent, timeout)
	defer cancel()
	request, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint.URL, nil)
	if err != nil {
		member.Reason = err.Error()
		return member
	}
	for name, value := range endpoint.Headers {
		request.Header.Set(name, value)
	}
	probeClient := endpoint.Client
	if probeClient == nil {
		probeClient = fallbackClient
	}
	response, requestErr := probeClient.Do(request)
	if requestErr != nil {
		member.Reason = requestErr.Error()
		return member
	}
	defer response.Body.Close()
	if response.StatusCode >= 200 && response.StatusCode < 300 {
		member.Ready, member.Reason = true, "AVAILABLE"
	} else {
		member.Reason = fmt.Sprintf("status=%s", response.Status)
	}
	return member
}

func fleetContext(ctx context.Context) context.Context { return ctx }