coder/coderd/x/chatd/chaterror/provider_error.go

package chaterror

import (
	"bufio"
	"bytes"
	"encoding/json"
	"errors"
	"io"
	"mime"
	"net/http"
	"regexp"
	"strconv"
	"strings"
	"time"

	"charm.land/fantasy"
)

// transportErrorPrefix matches the Anthropic SDK transport error format
// `METHOD "URL": <status> <status text> ` that wraps the real provider
// response body. The SDK emits this when it cannot parse a non-Anthropic
// response, so AWS Bedrock errors arrive through aibridge with this
// wrapper, hiding the useful message inside a trailing JSON body.
var transportErrorPrefix = regexp.MustCompile(`^[A-Z]+ "[^"]+": \d{3} `)

type providerErrorDetails struct {
	detail     string
	statusCode int
	retryAfter time.Duration
}

func extractProviderErrorDetails(err error) providerErrorDetails {
	var providerErr *fantasy.ProviderError
	if !errors.As(err, &providerErr) {
		return providerErrorDetails{}
	}

	return providerErrorDetails{
		detail:     providerErrorDetail(providerErr),
		statusCode: providerErr.StatusCode,
		retryAfter: retryAfterFromHeaders(providerErr.ResponseHeaders),
	}
}

func providerErrorDetail(providerErr *fantasy.ProviderError) string {
	if detail := providerErrorResponseMessage(providerErr.ResponseBody); detail != "" {
		return detail
	}
	// The Message fallback can also be the SDK transport wrapper (e.g. for
	// Bedrock via aibridge), so unwrap it for the same clean detail.
	return unwrapTransportErrorMessage(strings.TrimSpace(providerErr.Message))
}

// providerErrorResponseMessage extracts the human-readable message from a
// provider error response body after stripping any dumped HTTP status line
// and headers. It understands both the top-level `{"message":...}` shape
// used by many providers and the nested `{"error":{"message":...}}`
// envelope. When the extracted message is itself an SDK-formatted transport
// error wrapper, the clean inner provider message is returned. For
// non-JSON text/plain bodies (e.g. aibridge's budget errors) it returns
// the trimmed first line of the body; the result surfaces in the
// user-facing detail, so other content types (proxy HTML, opaque bodies)
// and valid JSON without an extractable message yield nothing.
func providerErrorResponseMessage(responseDump []byte) string {
	if len(responseDump) == 0 || len(responseDump) > 64*1024 {
		return ""
	}
	body, textPlain := readResponseDump(responseDump)
	if msg := unwrapTransportErrorMessage(jsonErrorMessage(body)); msg != "" {
		return msg
	}
	if !textPlain || json.Valid(body) {
		return ""
	}
	line, _, _ := strings.Cut(strings.TrimSpace(string(body)), "\n")
	return strings.TrimSpace(line)
}

// unwrapTransportErrorMessage extracts the clean provider message from an
// SDK-formatted wrapper such as:
//
//	POST "https://bedrock-runtime...": 400 Bad Request {"message":"..."}
//
// When the trailing body is JSON with a top-level "message" or a nested
// "error.message", that inner message is returned. Otherwise msg is
// returned unchanged.
func unwrapTransportErrorMessage(msg string) string {
	loc := transportErrorPrefix.FindStringIndex(msg)
	if loc == nil {
		return msg
	}
	// Search for the JSON body after the matched prefix so a brace inside
	// the URL or status text cannot be mistaken for the body.
	rest := msg[loc[1]:]
	start := strings.IndexByte(rest, '{')
	if start < 0 {
		return msg
	}
	if inner := jsonErrorMessage([]byte(rest[start:])); inner != "" {
		return inner
	}
	return msg
}

// jsonErrorMessage parses both the nested `{"error":{"message":...}}`
// envelope and the top-level `{"message":...}` shape used by many
// providers, preferring the nested form when present.
func jsonErrorMessage(body []byte) string {
	var env struct {
		Message string          `json:"message"`
		Error   json.RawMessage `json:"error"`
	}
	if err := json.Unmarshal(body, &env); err != nil {
		return ""
	}
	// Prefer the nested error.message when error is an object carrying one.
	// error may also be a non-object (string, array, number); tolerate that
	// and fall back to the top-level message instead of dropping it.
	if len(env.Error) > 0 {
		var inner struct {
			Message string `json:"message"`
		}
		if err := json.Unmarshal(env.Error, &inner); err == nil {
			if m := strings.TrimSpace(inner.Message); m != "" {
				return m
			}
		}
	}
	return strings.TrimSpace(env.Message)
}

// readResponseDump parses a dumped HTTP response into its body, removing
// the status line, headers, and any chunk framing, and reports whether the
// response declares Content-Type text/plain (ignoring media-type
// parameters such as charset). Payloads that do not parse as an HTTP
// response, such as the raw message fantasy's Google adapter stores in
// ResponseBody, are returned whole.
func readResponseDump(responseDump []byte) (body []byte, textPlain bool) {
	resp, err := http.ReadResponse(bufio.NewReader(bytes.NewReader(responseDump)), nil)
	if err != nil {
		return responseDump, false
	}
	defer resp.Body.Close()
	// The caller already bounds dumps at 64KB.
	body, err = io.ReadAll(resp.Body)
	if err != nil {
		return responseDump, false
	}
	mediaType, _, err := mime.ParseMediaType(resp.Header.Get("Content-Type"))
	return body, err == nil && mediaType == "text/plain"
}

func retryAfterFromHeaders(headers map[string]string) time.Duration {
	if len(headers) == 0 {
		return 0
	}

	// Prefer retry-after-ms (OpenAI convention, milliseconds)
	// over the standard retry-after (seconds or HTTP-date).
	for key, value := range headers {
		if strings.EqualFold(key, "retry-after-ms") {
			ms, err := strconv.ParseFloat(strings.TrimSpace(value), 64)
			if err == nil && ms > 0 {
				return time.Duration(ms * float64(time.Millisecond))
			}
		}
	}

	for key, value := range headers {
		if strings.EqualFold(key, "retry-after") {
			v := strings.TrimSpace(value)
			if seconds, err := strconv.ParseFloat(v, 64); err == nil {
				if seconds > 0 {
					return time.Duration(seconds * float64(time.Second))
				}
				return 0
			}
			if retryAt, err := http.ParseTime(v); err == nil {
				if d := time.Until(retryAt); d > 0 {
					return d
				}
			}
			return 0
		}
	}

	return 0
}