package tools

import (
	"context"
	"strings"

	"code.nochebuena.dev/einherjar/mcp/internal/index"
	"github.com/modelcontextprotocol/go-sdk/mcp"
)

type getExampleInput struct {
	Module string `json:"module" jsonschema:"the module name, e.g. core"`
	Topic  string `json:"topic,omitempty" jsonschema:"optional substring matched against the example title (case-insensitive)"`
}

type getExampleOutput struct {
	Examples []index.Example `json:"examples"`
}

func registerGetExample(s *mcp.Server, idx *index.Index) {
	mcp.AddTool(s, &mcp.Tool{
		Name:        "get_example",
		Description: "Return canonical usage examples for a module, extracted from its README. Filter by topic substring (e.g. 'Logger', 'Launcher') to narrow the result.",
	}, func(ctx context.Context, req *mcp.CallToolRequest, args getExampleInput) (*mcp.CallToolResult, getExampleOutput, error) {
		m := idx.FindModule(args.Module)
		if m == nil {
			return errorResult("module not found: " + args.Module), getExampleOutput{}, nil
		}
		needle := strings.ToLower(args.Topic)
		out := getExampleOutput{Examples: []index.Example{}}
		for _, ex := range m.Examples {
			if needle != "" && !strings.Contains(strings.ToLower(ex.Title), needle) {
				continue
			}
			out.Examples = append(out.Examples, ex)
		}
		return jsonText(out), out, nil
	})
}