package chatadvisor

import (
	"context"
	"encoding/json"
	"strings"

	"charm.land/fantasy"
)

// ToolName is the identifier the advisor tool registers under. The parent
// agent's exclusive-tool policy and the advisor-guidance block both reference
// this name, so keeping them synchronized requires a single source of truth.
const ToolName = "advisor"

// advisorQuestionMaxRunes caps the parent agent's question at a length
// that leaves room in the advisor prompt for system preamble and recent
// conversation context.
const advisorQuestionMaxRunes = 2000

// ToolOptions configures the built-in advisor tool.
type ToolOptions struct {
	Runtime                 *Runtime
	GetConversationSnapshot func() []fantasy.Message
	PublishAdviceDelta      func(toolCallID string, delta string)
	PublishAdviceReset      func(toolCallID string)
}

// Tool returns a fantasy.AgentTool that asks a nested model for concise
// strategic guidance. The nested advisor sees recent conversation
// context, runs without tools, and is limited to a single model step.
func Tool(opts ToolOptions) fantasy.AgentTool {
	return fantasy.NewAgentTool(
		ToolName,
		"Ask a separate advisor pass for strategic guidance about planning, architecture, tradeoffs, or debugging strategy. Provide a brief question of 2000 runes or fewer, summarizing context instead of pasting long logs or transcripts. The advisor sees recent conversation context, runs without tools for a single step, and responds to the parent agent rather than the end user.",
		func(ctx context.Context, args AdvisorArgs, call fantasy.ToolCall) (fantasy.ToolResponse, error) {
			if opts.Runtime == nil {
				return fantasy.NewTextErrorResponse("advisor runtime is not configured"), nil
			}
			if opts.GetConversationSnapshot == nil {
				return fantasy.NewTextErrorResponse("conversation snapshot provider is not configured"), nil
			}

			question := strings.TrimSpace(args.Question)
			if question == "" {
				return fantasy.NewTextErrorResponse("question is required"), nil
			}

			var runOpts *RunAdvisorOptions
			if call.ID != "" && (opts.PublishAdviceDelta != nil || opts.PublishAdviceReset != nil) {
				runOpts = &RunAdvisorOptions{}
				if opts.PublishAdviceDelta != nil {
					runOpts.OnAdviceDelta = func(delta string) {
						opts.PublishAdviceDelta(call.ID, delta)
					}
				}
				if opts.PublishAdviceReset != nil {
					runOpts.OnAdviceReset = func() {
						opts.PublishAdviceReset(call.ID)
					}
				}
			}

			result, err := opts.Runtime.RunAdvisor(ctx, question, opts.GetConversationSnapshot(), runOpts)
			if err != nil {
				return fantasy.NewTextErrorResponse(err.Error()), nil
			}
			data, err := json.Marshal(result)
			if err != nil {
				return fantasy.NewTextResponse("{}"), nil
			}
			return fantasy.NewTextResponse(string(data)), nil
		},
	)
}