// Package app wires the object graph. It is the one place that knows
// which concrete types satisfy the application's dependencies, so every
// other package can be constructed in a test with substitutes.
package app

import (
	"log/slog"

	"go.uber.org/fx"
	"go.uber.org/fx/fxevent"
	"sneak.berlin/go/simplexcalc/internal/config"
	"sneak.berlin/go/simplexcalc/internal/database"
	"sneak.berlin/go/simplexcalc/internal/globals"
	"sneak.berlin/go/simplexcalc/internal/handlers"
	"sneak.berlin/go/simplexcalc/internal/logger"
	"sneak.berlin/go/simplexcalc/internal/middleware"
	"sneak.berlin/go/simplexcalc/internal/render"
	"sneak.berlin/go/simplexcalc/internal/server"
	"sneak.berlin/go/simplexcalc/internal/telemetry"
)

// Module is every provider the service needs. Constructor order is
// irrelevant to fx; the order here is the order a reader wants: build
// metadata, logging, configuration, storage, then the HTTP layer.
//
//nolint:gochecknoglobals // an fx module is a declaration, not mutable state.
var Module = fx.Options(
	fx.Provide(
		globals.New,
		logger.New,
		config.New,
		database.New,
		telemetry.NewSentry,
		telemetry.NewMetrics,
		render.New,
		middleware.New,
		handlers.New,
		server.New,
	),

	// fx's own lifecycle events go through the application logger, so
	// the process emits one stream in one format. Without this, fx
	// prints its own plain-text output to stderr and a log pipeline
	// gets two formats from one process.
	fx.WithLogger(func(l *logger.Logger) fxevent.Logger {
		return &fxevent.SlogLogger{Logger: l.Get()}
	}),
)

// Invoke forces the graph to be built. fx constructs lazily: without a
// request for the Server, a perfectly valid App would start, construct
// nothing, and serve nothing.
//
//nolint:gochecknoglobals // as above.
var Invoke = fx.Invoke(func(_ *server.Server, log *logger.Logger, cfg *config.Config) {
	if cfg.Debug {
		log.EnableDebugLogging()
	}

	log.Identify()
})

// New builds the fx application for `serve`.
func New(opts ...fx.Option) *fx.App {
	return fx.New(append([]fx.Option{Module, Invoke}, opts...)...)
}

// DiscardLogger is a logger that writes nothing, for tests that build
// the graph and do not want its startup output.
func DiscardLogger() *slog.Logger {
	return slog.New(slog.DiscardHandler)
}