Add LLM interface

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

pkg/llm/errors.go

@@ -0,0 +1,70 @@
+// Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package llm
+
+import (
+	"fmt"
+	"time"
+)
+
+type (
+	ErrRateLimit struct {
+		RetryAfter time.Duration
+		Err        error
+	}
+
+	ErrContextLength struct {
+		MaxTokens int
+		Err       error
+	}
+
+	ErrContentFilter struct {
+		Err error
+	}
+
+	ErrAuthentication struct {
+		Err error
+	}
+)
+
+func (e *ErrRateLimit) Error() string {
+	if e.RetryAfter > 0 {
+		return fmt.Sprintf("rate limited (retry after %s): %v", e.RetryAfter, e.Err)
+	}
+	return fmt.Sprintf("rate limited: %v", e.Err)
+}
+
+func (e *ErrRateLimit) Unwrap() error { return e.Err }
+
+func (e *ErrContextLength) Error() string {
+	if e.MaxTokens > 0 {
+		return fmt.Sprintf("context length exceeded (max %d tokens): %v", e.MaxTokens, e.Err)
+	}
+	return fmt.Sprintf("context length exceeded: %v", e.Err)
+}
+
+func (e *ErrContextLength) Unwrap() error { return e.Err }
+
+func (e *ErrContentFilter) Error() string {
+	return fmt.Sprintf("content filtered: %v", e.Err)
+}
+
+func (e *ErrContentFilter) Unwrap() error { return e.Err }
+
+func (e *ErrAuthentication) Error() string {
+	return fmt.Sprintf("authentication failed: %v", e.Err)
+}
+
+func (e *ErrAuthentication) Unwrap() error { return e.Err }