package tools

import (
	"context"
	"strings"

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

type getConfigEnvInput struct {
	Module string `json:"module,omitempty" jsonschema:"restrict to one module's env vars, e.g. db-postgres or web. Omit to return every framework env var."`
}

type getConfigEnvOutput struct {
	Vars    []envspec.Var `json:"vars"`
	Count   int           `json:"count"`
	Summary string        `json:"summary"`
}

func registerGetConfigEnv(s *mcp.Server, idx *index.Index) {
	mcp.AddTool(s, &mcp.Tool{
		Name: "get_config_env",
		Description: "List the REAL environment variables an Einherjar component config reads, derived from the framework's struct tags (never hand-maintained). " +
			"Each entry gives the var name, the declaring module/struct/field, whether it is required, and its default. " +
			"Use this before composing a global Config or writing a .env — it is the source of truth for which EINHERJAR_* vars exist. " +
			"Pass a module (e.g. db-postgres, web, core, storage-minio) to scope it; omit to get all.",
	}, func(ctx context.Context, req *mcp.CallToolRequest, args getConfigEnvInput) (*mcp.CallToolResult, getConfigEnvOutput, error) {
		module := strings.TrimSpace(args.Module)
		var vars []envspec.Var
		if module == "" {
			vars = envspec.All(idx)
		} else {
			if idx.FindModule(module) == nil {
				return errorResult("module not found: " + module), getConfigEnvOutput{}, nil
			}
			vars = envspec.ForModule(idx, module)
		}
		if vars == nil {
			vars = []envspec.Var{}
		}
		out := getConfigEnvOutput{Vars: vars, Count: len(vars), Summary: summariseEnv(vars, module)}
		return jsonText(out), out, nil
	})
}

func summariseEnv(vars []envspec.Var, module string) string {
	var required int
	for _, v := range vars {
		if v.Required {
			required++
		}
	}
	scope := "the framework"
	if module != "" {
		scope = module
	}
	return itoa(len(vars)) + " env var(s) for " + scope + ", " + itoa(required) + " required."
}