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import mitt from '../../shared/lib/mitt'
import type { MittEmitter } from '../../shared/lib/mitt'
export type SpanOptions = {
startTime?: number
attributes?: Record<string, unknown>
}
export type SpanState =
| {
state: 'inprogress'
}
| {
state: 'ended'
endTime: number
}
interface ISpan {
name: string
startTime: number
attributes: Record<string, unknown>
state: SpanState
end(endTime?: number): void
}
class Span implements ISpan {
name: string
startTime: number
onSpanEnd: (span: Span) => void
state: SpanState
attributes: Record<string, unknown>
constructor(
name: string,
options: SpanOptions,
onSpanEnd: (span: Span) => void
) {
this.name = name
this.attributes = options.attributes ?? {}
this.startTime = options.startTime ?? Date.now()
this.onSpanEnd = onSpanEnd
this.state = { state: 'inprogress' }
}
end(endTime?: number) {
if (this.state.state === 'ended') {
throw new Error('Span has already ended')
}
this.state = {
state: 'ended',
endTime: endTime ?? Date.now(),
}
this.onSpanEnd(this)
}
}
class Tracer {
_emitter: MittEmitter<string> = mitt()
private handleSpanEnd = (span: Span) => {
this._emitter.emit('spanend', span)
}
startSpan(name: string, options: SpanOptions) {
return new Span(name, options, this.handleSpanEnd)
}
onSpanEnd(cb: (span: ISpan) => void): () => void {
this._emitter.on('spanend', cb)
return () => {
this._emitter.off('spanend', cb)
}
}
}
export type { ISpan as Span }
export default new Tracer()
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