// Package viewlog captures playback request events (manifest +
// segment fetches) to a blob.Store as gzipped JSONL files, so a later
// aggregation pass can derive view counts per place.stream.video.
//
// Goals at this layer: cheap to call from request handlers, non-
// blocking, durable enough that a periodic flush survives a crash
// with bounded data loss (the in-memory buffer between flushes).
//
// Privacy: IPs are HMAC'd with a daily-rotated salt held in localdb.
// Same IP collides within a UTC day (useful for dedup); the salt
// changes at midnight so cross-day correlation requires the original
// salt, which the operator can prune to enforce a retention horizon.
package viewlog

import "time"

// Event type tags.
const (
	EventTypeManifestRequest = "manifest_request"
	EventTypeSegmentRequest  = "segment_request"
)

// Manifest kinds populated on ManifestRequest events.
const (
	ManifestKindMaster = "master"
	ManifestKindMedia  = "media"
)

// Event is one line in the JSONL output. The Type field selects which
// of the per-type field groups are meaningful — empty fields are
// omitted on the wire to keep files small.
type Event struct {
	// Ts is the server's UTC clock at request time.
	Ts time.Time `json:"ts"`
	// Type is one of EventType*. Aggregators dispatch on this.
	Type string `json:"type"`
	// SID is the playback session id (atproto TID) the player carries
	// across manifest + segment fetches. Generated by the server on
	// the master playlist response and threaded through sub-playlist
	// + segment URLs from there.
	SID string `json:"sid,omitempty"`
	// IPHash is hex(HMAC-SHA256(daily_salt, ip)). Same IP, same UTC
	// day, same hash; salt rotation at midnight breaks correlation
	// across days. Empty when no IP could be resolved.
	IPHash string `json:"ip_hash,omitempty"`

	// --- manifest_request ---
	// VideoURI is the place.stream.video AT-URI the manifest is for.
	VideoURI string `json:"video_uri,omitempty"`
	// ManifestKind is "master" or "media".
	ManifestKind string `json:"manifest_kind,omitempty"`
	// Track is the muxlTrack id when ManifestKind == "media"; empty
	// for master playlists (those span every track).
	Track string `json:"track,omitempty"`

	// --- segment_request ---
	// CID is the content-addressed blob requested. For a playback
	// segment this is the MUXL container blob shared across the
	// video's tracks; for init segments it's the per-track init
	// blob. Aggregators join CID → place.stream.video via the
	// MediaTrack index.
	CID string `json:"cid,omitempty"`
	// OwnerDID is the repo DID the segment URL claims as the owner.
	// Lets the aggregator attribute traffic to a creator without a
	// CID lookup; verified upstream at the playback handler.
	OwnerDID string `json:"owner_did,omitempty"`
	// RangeStart / RangeEnd capture the HTTP Range bytes, when the
	// request asked for one. End is inclusive (matches RFC 7233).
	// Zero values indicate "whole blob" / "open-ended" range.
	RangeStart int64 `json:"range_start,omitempty"`
	RangeEnd   int64 `json:"range_end,omitempty"`
}