package aicra

import (
	"fmt"
	"io"
	"net/http"

	"git.xdrm.io/go/aicra/api"
	"git.xdrm.io/go/aicra/datatype"
	"git.xdrm.io/go/aicra/internal/config"
	"git.xdrm.io/go/aicra/internal/dynfunc"
)

// Builder for an aicra server
type Builder struct {
	conf     *config.Server
	handlers []*apiHandler
	adapters []api.Adapter
}

// represents an api handler (method-pattern combination)
type apiHandler struct {
	Method string
	Path   string
	dyn    *dynfunc.Handler
}

// AddType adds an available datatype to the api definition
func (b *Builder) AddType(t datatype.T) {
	if b.conf == nil {
		b.conf = &config.Server{}
	}
	if b.conf.Services != nil {
		panic(errLateType)
	}
	if b.conf.Types == nil {
		b.conf.Types = make([]datatype.T, 0)
	}
	b.conf.Types = append(b.conf.Types, t)
}

// Use adds an http adapter (middleware)
func (b *Builder) Use(adapter api.Adapter) {
	if b.conf == nil {
		b.conf = &config.Server{}
	}
	if b.adapters == nil {
		b.adapters = make([]api.Adapter, 0)
	}
	b.adapters = append(b.adapters, adapter)
}

// Setup the builder with its api definition file
// panics if already setup
func (b *Builder) Setup(r io.Reader) error {
	if b.conf == nil {
		b.conf = &config.Server{}
	}
	if b.conf.Services != nil {
		panic(errAlreadySetup)
	}
	return b.conf.Parse(r)
}

// Bind a dynamic handler to a REST service (method and pattern)
func (b *Builder) Bind(method, path string, fn interface{}) error {
	if b.conf.Services == nil {
		return errNotSetup
	}

	// find associated service from config
	var service *config.Service
	for _, s := range b.conf.Services {
		if method == s.Method && path == s.Pattern {
			service = s
			break
		}
	}

	if service == nil {
		return fmt.Errorf("%s '%s': %w", method, path, errUnknownService)
	}

	var dyn, err = dynfunc.Build(fn, *service)
	if err != nil {
		return fmt.Errorf("%s '%s' handler: %w", method, path, err)
	}

	b.handlers = append(b.handlers, &apiHandler{
		Path:   path,
		Method: method,
		dyn:    dyn,
	})

	return nil
}

// Get is equivalent to Bind(http.MethodGet)
func (b *Builder) Get(path string, fn interface{}) error {
	return b.Bind(http.MethodGet, path, fn)
}

// Post is equivalent to Bind(http.MethodPost)
func (b *Builder) Post(path string, fn interface{}) error {
	return b.Bind(http.MethodPost, path, fn)
}

// Put is equivalent to Bind(http.MethodPut)
func (b *Builder) Put(path string, fn interface{}) error {
	return b.Bind(http.MethodPut, path, fn)
}

// Delete is equivalent to Bind(http.MethodDelete)
func (b *Builder) Delete(path string, fn interface{}) error {
	return b.Bind(http.MethodDelete, path, fn)
}

// Build a fully-featured HTTP server
func (b Builder) Build() (http.Handler, error) {

	for _, service := range b.conf.Services {
		var isHandled bool
		for _, handler := range b.handlers {
			if handler.Method == service.Method && handler.Path == service.Pattern {
				isHandled = true
				break
			}
		}
		if !isHandled {
			return nil, fmt.Errorf("%s '%s': %w", service.Method, service.Pattern, errMissingHandler)
		}
	}

	return Handler(b), nil
}