package api_gen

import (
	"fmt"
	"go/types"
	"strings"

	"golang.org/x/tools/go/packages"
)

type APIPackage struct {
	PkgName   string
	PkgPath   string
	Files     []string
	Endpoints []Endpoint
	Types     map[string]types.Type
	Errors    []ErrorDef
}

type Endpoint struct {
	Name     string
	Method   string
	Path     string
	ImplName string
	ReqType  string
	ResType  string
}

type ErrorDef struct {
	Name string
	Type string
}

func parseAPIFiles(module string) (*APIPackage, error) {
	// Load the package with full type information
	cfg := &packages.Config{
		Mode: packages.NeedName |
			packages.NeedFiles |
			packages.NeedCompiledGoFiles |
			packages.NeedImports |
			packages.NeedDeps |
			packages.NeedTypes |
			packages.NeedSyntax |
			packages.NeedTypesInfo,
	}

	// TODO hard-coded
	pkgs, err := packages.Load(cfg, module)
	if err != nil {
		return nil, fmt.Errorf("failed to load package: %w", err)
	}

	if len(pkgs) == 0 {
		return nil, fmt.Errorf("no packages found")
	}

	if packages.PrintErrors(pkgs) > 0 {
		return nil, fmt.Errorf("package loading had errors")
	}

	pkg := pkgs[0]

	apiPkg := &APIPackage{
		PkgName: pkg.Name,
		PkgPath: pkg.PkgPath,
		Types:   make(map[string]types.Type),
	}

	if err := extractFromPackage(pkg, apiPkg); err != nil {
		return nil, err
	}

	return apiPkg, nil
}

func extractFromPackage(pkg *packages.Package, apiPkg *APIPackage) error {
	scope := pkg.Types.Scope()

	// Extract Path_* constants and link to types
	for _, name := range scope.Names() {
		obj := scope.Lookup(name)
		if obj == nil {
			continue
		}

		if tn, ok := obj.(*types.TypeName); ok {
			if named, ok := tn.Type().(*types.Named); ok {
				apiPkg.Types[name] = named
			}
		}

		if c, ok := obj.(*types.Const); ok {
			if strings.HasPrefix(name, "Path_") {

				val := c.Val().String()
				val = strings.Trim(val, `"`)
				parts := strings.SplitN(val, " ", 2)

				if len(parts) == 2 {
					endpointName := strings.TrimPrefix(name, "Path_")
					reqTypeName := endpointName + "Req"
					resTypeName := endpointName + "Res"

					endpoint := Endpoint{
						Name:    endpointName,
						Method:  parts[0],
						Path:    parts[1],
						ReqType: reqTypeName,
						ResType: resTypeName,
					}

					apiPkg.Endpoints = append(apiPkg.Endpoints, endpoint)
				}
			}
		}
	}

	return nil
}