package tools

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

	"github.com/mark3labs/mcp-go/mcp"
)

const FetchClusterEnvName = "fetch_cluster_env"

// NewFetchClusterEnvTool returns the schema for the fetch_cluster_env MCP Tool.
func NewFetchClusterEnvTool() mcp.Tool {
	return mcp.NewTool(FetchClusterEnvName,
		mcp.WithDescription("Fetch YARN cluster environment information and metrics from the ResourceManager."),
		mcp.WithString("cluster_id",
			mcp.Required(),
			mcp.Description("ID of the configured cluster (from list_clusters)"),
		),
	)
}

// FetchClusterEnvHandler fetches RM cluster info and metrics.
func (d *Deps) FetchClusterEnvHandler(ctx context.Context, req mcp.CallToolRequest) (*mcp.CallToolResult, error) {
	clusterID, err := req.RequireString("cluster_id")
	if err != nil {
		return errResult("fetch_cluster_env: " + err.Error()), nil
	}

	callLog := startToolCall(ctx, d.Logger, FetchClusterEnvName, map[string]any{
		"cluster_id": clusterID,
	})
	defer callLog.End()

	cl, err := d.ClusterRepo.Get(ctx, clusterID)
	if err != nil {
		callLog.WithError(err)
		return errResult("fetch_cluster_env: cluster " + clusterID + ": " + err.Error()), nil
	}

	base := strings.TrimRight(cl.RMURL, "/")
	infoBody, err := d.fetchInternal(ctx, cl, base+"/ws/v1/cluster/info")
	if err != nil {
		callLog.WithError(err)
		return errResult("fetch_cluster_env: info: " + err.Error()), nil
	}
	metricsBody, err := d.fetchInternal(ctx, cl, base+"/ws/v1/cluster/metrics")
	if err != nil {
		callLog.WithError(err)
		return errResult("fetch_cluster_env: metrics: " + err.Error()), nil
	}

	var info, metrics any
	_ = json.Unmarshal(infoBody, &info)
	_ = json.Unmarshal(metricsBody, &metrics)

	result := map[string]any{
		"cluster_info": info,
		"metrics":      metrics,
		"fetched_at":   time.Now().UTC().Format(time.RFC3339),
	}
	callLog.WithResult(map[string]any{"info_bytes": len(infoBody), "metrics_bytes": len(metricsBody)})
	return textResult(encodeJSON(result)), nil
}