package logging

import (
	"context"
	"errors"
	"fmt"
	"os"
	"time"

	"go.opentelemetry.io/contrib/bridges/otelzap"
	"go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploggrpc"
	"go.opentelemetry.io/otel/exporters/otlp/otlplog/otlploghttp"
	"go.opentelemetry.io/otel/log/global"
	"go.opentelemetry.io/otel/sdk/log"
	"go.uber.org/zap"
	"go.uber.org/zap/zapcore"

	"github.com/kanootoko/codevault/internal"
	"github.com/kanootoko/codevault/internal/config"
	"github.com/kanootoko/codevault/internal/observability"
)

func ConfigureLogger(ctx context.Context, cfg config.LoggingConfig, isProductionEnv bool) (logger *zap.Logger, closeFunc func(), err error) {
	stderrLevel, err := cfg.Stderr.ToZapLevel()
	if err != nil && !errors.Is(err, config.ErrLoggingDisabled) {
		return nil, nil, fmt.Errorf("error on getting stderr logging level: %w", err)
	}
	fileLoggers := make(map[string]zapcore.Level)
	for level, file := range cfg.Files {
		l, err := level.ToZapLevel()
		if err != nil {
			return nil, nil, fmt.Errorf("error on getting file logging level: %w", err)
		}
		fileLoggers[file] = l
	}
	var stderrEncoder zapcore.Encoder
	var fileEncoder zapcore.Encoder
	{
		var fileLoggerCfg zapcore.EncoderConfig
		var stderrLoggerCfg zapcore.EncoderConfig
		if isProductionEnv {
			fileLoggerCfg = zap.NewProductionEncoderConfig()
			stderrLoggerCfg = zap.NewProductionEncoderConfig()
		} else {
			fileLoggerCfg = zap.NewDevelopmentEncoderConfig()
			stderrLoggerCfg = zap.NewDevelopmentEncoderConfig()
		}
		fileLoggerCfg.TimeKey = "timestamp"
		fileLoggerCfg.EncodeTime = zapcore.ISO8601TimeEncoder

		stderrLoggerCfg.EncodeLevel = zapcore.CapitalColorLevelEncoder

		stderrEncoder = zapcore.NewConsoleEncoder(stderrLoggerCfg)
		fileEncoder = zapcore.NewJSONEncoder(fileLoggerCfg)
	}

	fileHandlers := make([]*os.File, 0, len(fileLoggers))
	zapWriters := make([]zapcore.Core, 0, len(fileLoggers)+1)
	for filename, level := range fileLoggers {
		fileHandler, err := os.Create(filename)
		if err != nil {
			for _, file := range fileHandlers[:len(fileHandlers)-1] {
				_ = file.Close()
			}
			return nil, nil, fmt.Errorf("error on log file creation: %w", err)
		}
		fileHandlers = append(fileHandlers, fileHandler)
		fileSync := zapcore.AddSync(fileHandler)
		zapWriters = append(zapWriters, zapcore.NewCore(fileEncoder, fileSync, zap.NewAtomicLevelAt(level)))
	}

	stderrSync := zapcore.AddSync(os.Stderr)
	if stderrLevel != zapcore.InvalidLevel {
		zapWriters = append(zapWriters, zapcore.NewCore(stderrEncoder, stderrSync, zap.NewAtomicLevelAt(stderrLevel)))
	}

	var otlpCloseFunc func()
	if cfg.Exporter.Level != "" {
		var otlpWriter zapcore.Core
		var err error
		otlpWriter, otlpCloseFunc, err = configureOtelLogging(ctx, cfg.Exporter)
		if err != nil {
			return nil, nil, fmt.Errorf("cannot configure OpenTelemetry log exporter: %w", err)
		}
		zapWriters = append(zapWriters, otlpWriter)
	}

	core := zapcore.NewTee(
		zapWriters...,
	)

	logger = zap.New(core)

	closeFunc = func() {
		_ = logger.Sync()
		for _, file := range fileHandlers {
			_ = file.Close()
		}
		if otlpCloseFunc != nil {
			otlpCloseFunc()
		}
	}

	logger.Info("configured logging", zap.Any("config", cfg))
	return
}

func configureOtelLogging(ctx context.Context, cfg config.LogsExporterConfig) (zapcore.Core, func(), error) {
	var exporter log.Exporter
	var err error
	if cfg.Transport == config.HTTPTransportType {
		exporter, err = otlploghttp.New(ctx, otlploghttp.WithEndpointURL(cfg.Endpoint))
	} else {
		exporter, err = otlploggrpc.New(ctx, otlploggrpc.WithEndpointURL(cfg.Endpoint))
	}
	if err != nil {
		return nil, nil, fmt.Errorf("cannot create OpenTelemetry logs exporter: %w", err)
	}
	res, err := observability.GetOtelResource()
	if err != nil {
		return nil, nil, fmt.Errorf("cannot get OpenTelemetry resource: %w", err)
	}

	provider := log.NewLoggerProvider(
		log.WithProcessor(log.NewBatchProcessor(exporter)),
		log.WithResource(res),
	)

	closeFunc := func() {
		shutdownContext, cancel := context.WithTimeout(context.Background(), time.Millisecond*300)
		defer cancel()
		_ = provider.ForceFlush(shutdownContext)
		_ = provider.Shutdown(shutdownContext)
		<-shutdownContext.Done()
	}
	global.SetLoggerProvider(provider)

	return otelzap.NewCore(internal.PackageName, otelzap.WithLoggerProvider(provider)), closeFunc, nil
}