// Package sessions — FleetClient calls the SandboxFleet controller REST API
// to assign sessions to fleet pods. This is the primary sandbox path;
// the raw-k8s SandboxManager is the fallback when the fleet controller
// is unavailable (e.g. during fleet rollout).
package sessions

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

const (
	defaultFleetControllerURL = "http://tool-definition-controller.poimen.svc.cluster.local:8788"
)

// FleetClient calls the SandboxFleet controller REST API.
type FleetClient struct {
	baseURL string
	client  *http.Client
}

// FleetAssignResult is returned by the controller assign endpoint.
type FleetAssignResult struct {
	PodSvcDns string `json:"podSvcDns"`
	PodName   string `json:"podName"`
}

// NewFleetClient creates a FleetClient from env or default URL.
// FLEET_CONTROLLER_URL — default: defaultFleetControllerURL
func NewFleetClient() *FleetClient {
	url := os.Getenv("FLEET_CONTROLLER_URL")
	if url == "" {
		url = defaultFleetControllerURL
	}
	return &FleetClient{
		baseURL: url,
		client:  &http.Client{Timeout: 35 * time.Second},
	}
}

// Assign asks the fleet controller to assign sessionID to a fleet pod.
// Returns the pod's ClusterIP service DNS and pod name.
func (f *FleetClient) Assign(ctx context.Context, sessionID string) (*FleetAssignResult, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodPost,
		f.baseURL+"/sessions/"+sessionID+"/assign", nil)
	if err != nil {
		return nil, fmt.Errorf("build request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := f.client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("fleet controller unreachable: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 300 {
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 512))
		return nil, fmt.Errorf("fleet controller returned %d: %s", resp.StatusCode, body)
	}

	var result FleetAssignResult
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return nil, fmt.Errorf("decode: %w", err)
	}
	if result.PodSvcDns == "" {
		return nil, fmt.Errorf("fleet controller returned empty podSvcDns")
	}
	return &result, nil
}

// Release notifies the fleet controller that a session has ended.
// Cleans up the per-session ServiceAccount (audit trail SA).
// Non-fatal: fleet controller handles this async.
func (f *FleetClient) Release(ctx context.Context, sessionID string) error {
	req, err := http.NewRequestWithContext(ctx, http.MethodDelete,
		f.baseURL+"/sessions/"+sessionID, bytes.NewReader(nil))
	if err != nil {
		return fmt.Errorf("build request: %w", err)
	}
	resp, err := f.client.Do(req)
	if err != nil {
		return fmt.Errorf("fleet controller unreachable: %w", err)
	}
	defer resp.Body.Close()
	if resp.StatusCode >= 300 {
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 512))
		return fmt.Errorf("fleet controller returned %d: %s", resp.StatusCode, body)
	}
	return nil
}