File size: 8,299 Bytes
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import { ToolFailure } from "@opencode-ai/llm"
import { Duration, Effect, Layer, Schema } from "effect"
import { HttpClient, HttpClientRequest, HttpClientResponse } from "effect/unstable/http"
import { Parser } from "htmlparser2"
import TurndownService from "turndown"
import { makeLocationNode } from "../effect/app-node"
import { LayerNodePlatform } from "../effect/app-node-platform"
import { PermissionV2 } from "../permission"
import { collectBoundedResponseBody } from "./http-body"
import { ToolRegistry } from "./registry"
import { Tool } from "./tool"
import { Tools } from "./tools"
export const name = "webfetch"
export const MAX_RESPONSE_BYTES = 5 * 1024 * 1024
export const DEFAULT_TIMEOUT_SECONDS = 30
export const MAX_TIMEOUT_SECONDS = 120
export const description = `Fetch content from an HTTP or HTTPS URL and return it as text, markdown, or HTML. Markdown is the default.
Use a more targeted tool when one is available. This tool is read-only. Large text results may be replaced with a preview while the complete output is retained in managed storage.`
const Timeout = Schema.Number.check(Schema.isGreaterThan(0), Schema.isLessThanOrEqualTo(MAX_TIMEOUT_SECONDS))
export const Input = Schema.Struct({
url: Schema.String.annotate({ description: "The HTTP or HTTPS URL to fetch content from" }),
format: Schema.Literals(["text", "markdown", "html"])
.annotate({ description: "The format to return the content in. Defaults to markdown." })
.pipe(Schema.withDecodingDefault(Effect.succeed("markdown" as const))),
timeout: Timeout.pipe(Schema.optional).annotate({
description: `Optional timeout in seconds (maximum: ${MAX_TIMEOUT_SECONDS})`,
}),
})
const Output = Schema.Struct({
url: Schema.String,
contentType: Schema.String,
format: Input.fields.format,
output: Schema.String,
})
type Format = (typeof Input.Type)["format"]
const acceptHeader = (format: Format) => {
switch (format) {
case "markdown":
return "text/markdown;q=1.0, text/x-markdown;q=0.9, text/plain;q=0.8, text/html;q=0.7, */*;q=0.1"
case "text":
return "text/plain;q=1.0, text/markdown;q=0.9, text/html;q=0.8, */*;q=0.1"
case "html":
return "text/html;q=1.0, application/xhtml+xml;q=0.9, text/plain;q=0.8, text/markdown;q=0.7, */*;q=0.1"
}
return "*/*"
}
const headers = (format: Format, userAgent: string) => ({
"User-Agent": userAgent,
Accept: acceptHeader(format),
"Accept-Language": "en-US,en;q=0.9",
})
const browserUserAgent =
"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/143.0.0.0 Safari/537.36"
const isCloudflareChallenge = (error: unknown) => {
if (!error || typeof error !== "object" || !("reason" in error)) return false
const reason = error.reason
if (
!reason ||
typeof reason !== "object" ||
!("_tag" in reason) ||
reason._tag !== "StatusCodeError" ||
!("response" in reason)
)
return false
const response = reason.response as HttpClientResponse.HttpClientResponse
return response.status === 403 && response.headers["cf-mitigated"] === "challenge"
}
const request = (url: string, format: Format, userAgent = browserUserAgent) =>
HttpClientRequest.get(url).pipe(HttpClientRequest.setHeaders(headers(format, userAgent)))
const assertHttpUrl = (url: URL) => {
if (url.protocol !== "http:" && url.protocol !== "https:") throw new Error("URL must use http:// or https://")
}
const execute = (http: HttpClient.HttpClient, url: string, format: Format, userAgent = browserUserAgent) =>
http.execute(request(url, format, userAgent)).pipe(Effect.flatMap(HttpClientResponse.filterStatusOk))
const collectBody = (response: HttpClientResponse.HttpClientResponse) =>
collectBoundedResponseBody(
response,
MAX_RESPONSE_BYTES,
() => new Error(`Response too large (exceeds ${MAX_RESPONSE_BYTES} byte limit)`),
)
const mimeFrom = (contentType: string) => contentType.split(";", 1)[0]?.trim().toLowerCase() ?? ""
const isImageAttachment = (mime: string) =>
mime.startsWith("image/") && mime !== "image/svg+xml" && mime !== "image/vnd.fastbidsheet"
const isTextualMime = (mime: string) =>
!mime ||
mime.startsWith("text/") ||
mime === "application/json" ||
mime.endsWith("+json") ||
mime === "application/xml" ||
mime.endsWith("+xml") ||
mime === "application/javascript" ||
mime === "application/x-javascript"
const convert = (content: string, contentType: string, format: Format) => {
if (!contentType.includes("text/html")) return content
if (format === "markdown") return convertHTMLToMarkdown(content)
if (format === "text") return extractTextFromHTML(content)
return content
}
const layer = Layer.effectDiscard(
Effect.gen(function* () {
const tools = yield* Tools.Service
const http = yield* HttpClient.HttpClient
const permission = yield* PermissionV2.Service
yield* tools
.register({
[name]: Tool.make({
description,
input: Input,
output: Output,
toModelOutput: ({ output }) => [{ type: "text", text: output.output }],
execute: (input, context) =>
Effect.gen(function* () {
yield* Effect.try({
try: () => assertHttpUrl(new URL(input.url)),
catch: (error) => error,
})
yield* permission.assert({
action: name,
resources: [input.url],
save: ["*"],
metadata: input,
sessionID: context.sessionID,
agent: context.agent,
source: { type: "tool", messageID: context.assistantMessageID, callID: context.toolCallID },
})
const { body, contentType } = yield* Effect.gen(function* () {
const response = yield* execute(http, input.url, input.format).pipe(
Effect.catchIf(isCloudflareChallenge, () => execute(http, input.url, input.format, "opencode")),
)
const contentType = response.headers["content-type"] || ""
const mime = mimeFrom(contentType)
if (isImageAttachment(mime))
return yield* Effect.fail(new Error(`Unsupported fetched image content type: ${mime}`))
if (!isTextualMime(mime))
return yield* Effect.fail(new Error(`Unsupported fetched file content type: ${mime}`))
return { body: yield* collectBody(response), contentType }
}).pipe(
Effect.timeoutOrElse({
duration: Duration.seconds(input.timeout ?? DEFAULT_TIMEOUT_SECONDS),
orElse: () => Effect.fail(new Error("Request timed out")),
}),
)
const content = new TextDecoder().decode(body)
const output = yield* Effect.try({
try: () => convert(content, contentType, input.format),
catch: (error) => error,
})
return {
url: input.url,
contentType,
format: input.format,
output,
}
}).pipe(Effect.mapError(() => new ToolFailure({ message: `Unable to fetch ${input.url}` }))),
}),
})
.pipe(Effect.orDie)
}),
)
export const node = makeLocationNode({
name: "tool/webfetch",
layer,
deps: [ToolRegistry.node, PermissionV2.node, LayerNodePlatform.httpClient],
})
export function extractTextFromHTML(html: string) {
let text = ""
let skipDepth = 0
const parser = new Parser({
onopentag(name) {
if (skipDepth > 0 || ["script", "style", "noscript", "iframe", "object", "embed"].includes(name)) skipDepth++
},
ontext(input) {
if (skipDepth === 0) text += input
},
onclosetag() {
if (skipDepth > 0) skipDepth--
},
})
parser.write(html)
parser.end()
return text.trim()
}
export function convertHTMLToMarkdown(html: string) {
const turndown = new TurndownService({
headingStyle: "atx",
hr: "---",
bulletListMarker: "-",
codeBlockStyle: "fenced",
emDelimiter: "*",
})
turndown.remove(["script", "style", "meta", "link"])
return turndown.turndown(html)
}
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