package proxy

import (
	"context"
	"net/url"

	"forge.cadoles.com/Cadoles/emissary/internal/agent"
	"forge.cadoles.com/Cadoles/emissary/internal/proxy"
	spec "forge.cadoles.com/Cadoles/emissary/internal/spec/proxy"
	"github.com/mitchellh/hashstructure/v2"
	"github.com/pkg/errors"
	"gitlab.com/wpetit/goweb/logger"
)

type proxyEntry struct {
	SpecHash uint64
	Proxy    *ReverseProxy
}

type Controller struct {
	proxies map[spec.ID]*proxyEntry
}

// Name implements node.Controller.
func (c *Controller) Name() string {
	return "proxy-controller"
}

// Reconcile implements node.Controller.
func (c *Controller) Reconcile(ctx context.Context, state *agent.State) error {
	proxySpec := spec.NewSpec()

	if err := state.GetSpec(spec.NameProxy, proxySpec); err != nil {
		if errors.Is(err, agent.ErrSpecNotFound) {
			logger.Info(ctx, "could not find proxy spec")

			c.stopAllProxies(ctx)

			return nil
		}

		return errors.WithStack(err)
	}

	logger.Info(ctx, "retrieved spec", logger.F("spec", proxySpec.SpecName()), logger.F("revision", proxySpec.SpecRevision()))

	c.updateProxies(ctx, proxySpec)

	return nil
}

func (c *Controller) stopAllProxies(ctx context.Context) {
	if len(c.proxies) > 0 {
		logger.Info(ctx, "stopping all proxies")
	}

	for proxyID, entry := range c.proxies {
		logger.Info(ctx, "stopping proxy", logger.F("proxyID", proxyID))

		if err := entry.Proxy.Stop(); err != nil {
			err = errors.WithStack(err)
			logger.Error(
				ctx, "error while stopping proxy",
				logger.F("proxyID", proxyID),
				logger.CapturedE(err),
			)

			delete(c.proxies, proxyID)
		}
	}
}

func (c *Controller) updateProxies(ctx context.Context, spec *spec.Spec) {
	// Stop and remove obsolete proxys
	for proxyID, entry := range c.proxies {
		if _, exists := spec.Proxies[proxyID]; exists {
			continue
		}

		logger.Info(ctx, "stopping proxy", logger.F("proxyID", proxyID))

		if err := entry.Proxy.Stop(); err != nil {
			err = errors.WithStack(err)
			logger.Error(
				ctx, "error while stopping proxy",
				logger.F("proxyID", proxyID),
				logger.CapturedE(err),
			)

			delete(c.proxies, proxyID)
		}
	}

	// (Re)start proxys
	for proxyID, proxySpec := range spec.Proxies {
		proxyCtx := logger.With(ctx, logger.F("proxyID", proxyID))

		if err := c.updateProxy(ctx, proxyID, proxySpec); err != nil {
			err = errors.WithStack(err)
			logger.Error(proxyCtx, "could not update proxy", logger.CapturedE(err))
			continue
		}
	}
}

func (c *Controller) updateProxy(ctx context.Context, proxyID spec.ID, proxySpec spec.ProxyEntry) (err error) {
	newProxySpecHash, err := hashstructure.Hash(proxySpec, hashstructure.FormatV2, nil)
	if err != nil {
		return errors.WithStack(err)
	}

	var entry *proxyEntry

	entry, exists := c.proxies[proxyID]
	if !exists {
		logger.Info(ctx, "proxy currently not running")
	}

	if entry == nil {
		entry = &proxyEntry{
			Proxy:    NewReverseProxy(),
			SpecHash: 0,
		}

		c.proxies[proxyID] = entry
	}

	specChanged := newProxySpecHash != entry.SpecHash

	if entry.Proxy.Running() && !specChanged {
		return nil
	}

	if specChanged && entry.SpecHash != 0 {
		logger.Info(
			ctx, "restarting proxy",
			logger.F("address", proxySpec.Address),
		)
	} else {
		logger.Info(
			ctx, "starting proxy",
			logger.F("address", proxySpec.Address),
		)
	}

	options := make([]proxy.OptionFunc, 0)
	allowedHosts := make([]string, len(proxySpec.Mappings))
	mappings := make(map[string]*url.URL, len(proxySpec.Mappings))

	for _, m := range proxySpec.Mappings {
		target, err := url.Parse(m.Target)
		if err != nil {
			return errors.WithStack(err)
		}

		mappings[m.HostPattern] = target
		allowedHosts = append(allowedHosts, m.HostPattern)
	}

	options = append(
		options,
		proxy.WithAllowedHosts(allowedHosts...),
		proxy.WithRewriteHosts(mappings),
	)

	if err := entry.Proxy.Start(ctx, proxySpec.Address, options...); err != nil {
		delete(c.proxies, proxyID)

		return errors.Wrap(err, "could not start app")
	}

	entry.SpecHash = newProxySpecHash

	return nil
}

func NewController() *Controller {
	return &Controller{
		proxies: make(map[spec.ID]*proxyEntry),
	}
}

var _ agent.Controller = &Controller{}