Add LLM interface

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

pkg/llm/message.go

@@ -0,0 +1,52 @@
+// 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 "encoding/json"
+
+type (
+	Message struct {
+		Role       Role
+		Parts      []Part
+		ToolCalls  []ToolCall
+		ToolCallID string // set when Role is RoleTool
+	}
+
+	ToolCall struct {
+		ID       string
+		Function FunctionCall
+	}
+
+	FunctionCall struct {
+		Name      string
+		Arguments string // JSON-encoded arguments
+	}
+
+	Tool struct {
+		Name        string
+		Description string
+		Parameters  json.RawMessage // JSON Schema
+	}
+)
+
+func (m Message) Text() string {
+	var s string
+	for _, p := range m.Parts {
+		if tp, ok := p.(TextPart); ok {
+			s += tp.Text
+		}
+	}
+	return s
+}