// Bridge — typed HTTP client for HarborForge.Backend's calendar API.
// Endpoint shapes verified via the backend's /openapi.json and against
// HarborForge.OpenclawPlugin/plugin/calendar/calendar-bridge.ts so
// the two plugins drop into the same backend without per-plugin
// adapters.

package calendar

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

// Bridge is constructed once per scheduler and reused across heartbeats.
type Bridge struct {
	BaseURL        string
	ClawIdentifier string
	HTTP           *http.Client
}

// New constructs a bridge with a 20s default timeout.
func New(baseURL, clawIdentifier string) *Bridge {
	return &Bridge{
		BaseURL:        strings.TrimRight(baseURL, "/"),
		ClawIdentifier: clawIdentifier,
		HTTP:           &http.Client{Timeout: 20 * time.Second},
	}
}

// Heartbeat POSTs /calendar/agent/heartbeat. Per-agent: each running
// agent on this claw drives its own heartbeat (matches OpenClaw plugin
// semantics).
func (b *Bridge) Heartbeat(ctx context.Context, agentID string) (HeartbeatResponse, error) {
	body := HeartbeatRequest{ClawIdentifier: b.ClawIdentifier, AgentID: agentID}
	raw, err := b.doJSON(ctx, http.MethodPost, "/calendar/agent/heartbeat", agentID, body)
	if err != nil {
		return HeartbeatResponse{}, err
	}
	var out HeartbeatResponse
	if len(raw) > 0 {
		if err := json.Unmarshal(raw, &out); err != nil {
			return HeartbeatResponse{}, fmt.Errorf("decode heartbeat: %w (body=%q)", err, truncate(raw, 200))
		}
	}
	return out, nil
}

// UpdateRealSlot PATCHes /calendar/slots/{id}/agent-update.
func (b *Bridge) UpdateRealSlot(ctx context.Context, agentID string, slotID int64, update SlotAgentUpdate) error {
	path := "/calendar/slots/" + strconv.FormatInt(slotID, 10) + "/agent-update"
	_, err := b.doJSON(ctx, http.MethodPatch, path, agentID, update)
	return err
}

// UpdateVirtualSlot PATCHes /calendar/slots/virtual/{vid}/agent-update.
// The backend materialises the virtual slot first; subsequent calls
// against the same logical slot should use UpdateRealSlot with the
// id returned in the response — but for v1 we don't round-trip the
// materialised id back to the scheduler (would require a separate
// fetch); the agent-update path tolerates re-PATCHing a virtual id.
func (b *Bridge) UpdateVirtualSlot(ctx context.Context, agentID string, virtualID string, update SlotAgentUpdate) error {
	path := "/calendar/slots/virtual/" + virtualID + "/agent-update"
	_, err := b.doJSON(ctx, http.MethodPatch, path, agentID, update)
	return err
}

// PushAgentStatus POSTs /calendar/agent/status. Used to push idle ↔
// busy transitions out of the normal heartbeat cycle.
func (b *Bridge) PushAgentStatus(ctx context.Context, agentID string, status AgentStatusValue) error {
	body := AgentStatusPush{
		ClawIdentifier: b.ClawIdentifier, AgentID: agentID, Status: status,
	}
	_, err := b.doJSON(ctx, http.MethodPost, "/calendar/agent/status", agentID, body)
	return err
}

// doJSON serialises body, attaches the two auth headers, and returns
// the response bytes. Errors on non-2xx with truncated body.
func (b *Bridge) doJSON(ctx context.Context, method, path, agentID string, body any) ([]byte, error) {
	if agentID == "" {
		return nil, errors.New("calendar: agent_id required for auth headers")
	}
	raw, err := json.Marshal(body)
	if err != nil {
		return nil, fmt.Errorf("marshal %s %s: %w", method, path, err)
	}
	req, err := http.NewRequestWithContext(ctx, method, b.BaseURL+path, bytes.NewReader(raw))
	if err != nil {
		return nil, err
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("X-Agent-ID", agentID)
	req.Header.Set("X-Claw-Identifier", b.ClawIdentifier)

	res, err := b.HTTP.Do(req)
	if err != nil {
		return nil, fmt.Errorf("%s %s: %w", method, path, err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	if res.StatusCode < 200 || res.StatusCode >= 300 {
		return nil, fmt.Errorf("%s %s → %d: %s",
			method, path, res.StatusCode, truncate(out, 300))
	}
	return out, nil
}

func truncate(b []byte, n int) string {
	if len(b) <= n {
		return string(b)
	}
	return string(b[:n]) + "…"
}