package cli

import (
	"context"
	"io"
	"log/slog"
	"os"
	"path/filepath"
	"strings"

	"github.com/spf13/cobra"

	"github.com/neilotoole/sq/cli/config"
	"github.com/neilotoole/sq/cli/flag"
	"github.com/neilotoole/sq/libsq/core/errz"
	"github.com/neilotoole/sq/libsq/core/lg"
	"github.com/neilotoole/sq/libsq/core/lg/lga"
	"github.com/neilotoole/sq/libsq/core/lg/userlogdir"
	"github.com/neilotoole/sq/libsq/core/options"
	"github.com/neilotoole/sq/libsq/core/stringz"
)

var (
	OptLogEnabled = options.NewBool(
		"log",
		"",
		0,
		false,
		"Enable logging",
		"Enable logging.",
	)

	OptLogFile = options.NewString(
		"log.file",
		"",
		0,
		getDefaultLogFilePath(),
		nil,
		"Log file path",
		`Path to log file. Empty value disables logging.`,
	)

	OptLogLevel = NewLogLevelOpt(
		"log.level",
		slog.LevelDebug,
		`Log level, one of: DEBUG, INFO, WARN, ERROR`,
		"Log level, one of: DEBUG, INFO, WARN, ERROR.",
	)
)

// defaultLogging returns a *slog.Logger, its slog.Handler, and
// possibly a *cleanup.Cleanup, which the caller is responsible
// for invoking at the appropriate time. If an error is returned, the
// other returned values will be nil. If logging is not enabled,
// the returned values will also be nil.
func defaultLogging(ctx context.Context, osArgs []string, cfg *config.Config,
) (log *slog.Logger, h slog.Handler, closer func() error, err error) {
	bootLog := lg.FromContext(ctx)

	enabled := getLogEnabled(ctx, osArgs, cfg)
	if !enabled {
		return nil, nil, nil, nil
	}

	// First, get the log file path. It can come from flag, envar, or config.
	logFilePath := strings.TrimSpace(getLogFilePath(ctx, osArgs, cfg))
	if logFilePath == "" {
		bootLog.Debug("Logging: not enabled (log file path not set)")
		return nil, nil, nil, nil
	}

	lvl := getLogLevel(ctx, osArgs, cfg)

	// Allow for $HOME/sq.log etc.
	logFilePath = os.ExpandEnv(logFilePath)
	bootLog.Debug("Logging: enabled", lga.Path, logFilePath)

	// Let's try to create the dir holding the logfile... if it already exists,
	// then os.MkdirAll will just no-op
	parent := filepath.Dir(logFilePath)
	err = os.MkdirAll(parent, 0o750)
	if err != nil {
		return nil, nil, nil, errz.Wrapf(err, "logging: failed to create parent dir of log file %s", logFilePath)
	}

	logFile, err := os.OpenFile(logFilePath, os.O_RDWR|os.O_CREATE|os.O_APPEND, 0o600)
	if err != nil {
		return nil, nil, nil, errz.Wrapf(err, "logging: unable to open log file: %s", logFilePath)
	}
	closer = logFile.Close

	h = newJSONHandler(logFile, lvl)
	return slog.New(h), h, closer, nil
}

func stderrLogger() (*slog.Logger, slog.Handler) {
	h := newJSONHandler(os.Stderr, slog.LevelDebug)
	return slog.New(h), h
}

func newJSONHandler(w io.Writer, lvl slog.Leveler) slog.Handler {
	h := &slog.HandlerOptions{
		AddSource:   true,
		Level:       lvl,
		ReplaceAttr: slogReplaceAttrs,
	}

	return slog.NewJSONHandler(w, h)
}

func slogReplaceAttrs(groups []string, a slog.Attr) slog.Attr {
	a = slogReplaceSource(groups, a)
	a = slogReplaceDuration(groups, a)
	return a
}

// slogReplaceSource overrides the default slog.SourceKey attr
// to print "pkg/file.go" instead.
func slogReplaceSource(_ []string, a slog.Attr) slog.Attr {
	// We want source to be "pkg/file.go".
	if a.Key == slog.SourceKey {
		fp := a.Value.String()
		a.Value = slog.StringValue(filepath.Join(filepath.Base(filepath.Dir(fp)), filepath.Base(fp)))
	}
	return a
}

// slogReplaceDuration prints the friendly version of duration.
func slogReplaceDuration(_ []string, a slog.Attr) slog.Attr {
	if a.Value.Kind() == slog.KindDuration {
		a.Value = slog.StringValue(a.Value.Duration().String())
	}
	return a
}

// logFrom is a convenience function for getting a *slog.Logger from a
// *cobra.Command or context.Context.
// If no logger present, lg.Discard() is returned.
func logFrom(cmd *cobra.Command) *slog.Logger {
	if cmd == nil {
		return lg.Discard()
	}

	ctx := cmd.Context()
	if ctx == nil {
		return lg.Discard()
	}

	log := lg.FromContext(ctx)
	if log == nil {
		return lg.Discard()
	}

	return log
}

// getLogEnabled determines if logging is enabled based on flags, envars, or config.
// Any error is logged to the ctx logger.
func getLogEnabled(ctx context.Context, osArgs []string, cfg *config.Config) bool {
	bootLog := lg.FromContext(ctx)
	var enabled bool

	val, ok, err := getBootstrapFlagValue(flag.LogEnabled, "", flag.LogEnabledUsage, osArgs)
	if err != nil {
		bootLog.Error("Reading log 'enabled' from flag", lga.Flag, flag.LogEnabled, lga.Err, err)
	}
	if ok {
		bootLog.Debug("Using log 'enabled' specified via flag", lga.Flag, flag.LogEnabled, lga.Val, val)

		enabled, err = stringz.ParseBool(val)
		if err != nil {
			bootLog.Error(
				"Reading bool flag",
				lga.Flag, flag.LogEnabled,
				lga.Val, val,
			)
			// When in doubt, enable logging?
			return true
		}

		return enabled
	}

	val, ok = os.LookupEnv(config.EnvarLogEnabled)
	if ok {
		bootLog.Debug("Using log 'enabled' specified via envar",
			lga.Env, config.EnvarLogEnabled,
			lga.Val, val,
		)

		enabled, err = stringz.ParseBool(val)
		if err != nil {
			bootLog.Error(
				"Reading bool envar",
				lga.Env, config.EnvarLogEnabled,
				lga.Val, val,
			)

			// When in doubt, enable logging?
			return true
		}

		return enabled
	}

	var o options.Options
	if cfg != nil {
		o = cfg.Options
	}

	enabled = OptLogEnabled.Get(o)
	bootLog.Debug("Using log 'enabled' specified via config", lga.Key, OptLogEnabled.Key(), lga.Val, enabled)
	return enabled
}

// getLogLevel gets the log level, based on flags, envars, or config.
// Any error is logged to the ctx logger.
func getLogLevel(ctx context.Context, osArgs []string, cfg *config.Config) slog.Level {
	bootLog := lg.FromContext(ctx)

	val, ok, err := getBootstrapFlagValue(flag.LogLevel, "", flag.LogLevelUsage, osArgs)
	if err != nil {
		bootLog.Error("Reading log level from flag", lga.Flag, flag.LogLevel, lga.Err, err)
	}
	if ok {
		bootLog.Debug("Using log level specified via flag", lga.Flag, flag.LogLevel, lga.Val, val)

		lvl := new(slog.Level)
		if err = lvl.UnmarshalText([]byte(val)); err != nil {
			bootLog.Error("Invalid log level specified via flag",
				lga.Flag, flag.LogLevel,
				lga.Val, val,
				lga.Err, err)
		} else {
			return *lvl
		}
	}

	val, ok = os.LookupEnv(config.EnvarLogLevel)
	if ok {
		bootLog.Debug("Using log level specified via envar",
			lga.Env, config.EnvarLogLevel,
			lga.Val, val)

		lvl := new(slog.Level)
		if err = lvl.UnmarshalText([]byte(val)); err != nil {
			bootLog.Error("Invalid log level specified by envar",
				lga.Env, config.EnvarLogLevel,
				lga.Val, val,
				lga.Err, err)
		} else {
			return *lvl
		}
	}

	var o options.Options
	if cfg != nil {
		o = cfg.Options
	}

	lvl := OptLogLevel.Get(o)
	bootLog.Debug("Using log level specified via config", lga.Key, OptLogLevel.Key(), lga.Val, lvl)
	return lvl
}

// getLogFilePath gets the log file path, based on flags, envars, or config.
// If a log file is not specified (and thus logging is disabled), empty string
// is returned.
func getLogFilePath(ctx context.Context, osArgs []string, cfg *config.Config) string {
	bootLog := lg.FromContext(ctx)

	fp, ok, err := getBootstrapFlagValue(flag.LogFile, "", flag.LogFileUsage, osArgs)
	if err != nil {
		bootLog.Error("Reading log file from flag", lga.Flag, flag.LogFile, lga.Err, err)
	}
	if ok {
		bootLog.Debug("Log file specified via flag", lga.Flag, flag.LogFile, lga.Path, fp)
		return fp
	}

	fp, ok = os.LookupEnv(config.EnvarLogPath)
	if ok {
		bootLog.Debug("Log file specified via envar", lga.Env, config.EnvarLogPath, lga.Path, fp)
		return fp
	}

	var o options.Options
	if cfg != nil {
		o = cfg.Options
	}

	fp = OptLogFile.Get(o)
	bootLog = bootLog.With(lga.Key, OptLogFile.Key(), lga.Path, fp)

	if !o.IsSet(OptLogFile) {
		bootLog.Debug("Log file not explicitly set in config; using default")
		return fp
	}

	if fp == "" {
		bootLog.Debug(`Log file explicitly set to "" in config; logging disabled`)
	}

	bootLog.Debug("Log file specified via config")
	return fp
}

// getDefaultLogFilePath returns the OS-dependent log file path,
// or an empty string if it can't be determined. The file (and its
// parent dir) may not exist.
func getDefaultLogFilePath() string {
	p, err := userlogdir.UserLogDir()
	if err != nil {
		return ""
	}

	return filepath.Join(p, "sq", "sq.log")
}

var _ options.Opt = LogLevelOpt{}

// NewLogLevelOpt returns a new LogLevelOpt instance.
func NewLogLevelOpt(key string, defaultVal slog.Level, usage, help string) LogLevelOpt {
	opt := options.NewBaseOpt(key, "", 0, usage, help)
	return LogLevelOpt{BaseOpt: opt, defaultVal: defaultVal}
}

// LogLevelOpt is an options.Opt for slog.Level.
type LogLevelOpt struct {
	options.BaseOpt
	defaultVal slog.Level
}

// Process implements options.Processor. It converts matching
// string values in o into slog.Level. If no match found,
// the input arg is returned unchanged. Otherwise, a clone is
// returned.
func (op LogLevelOpt) Process(o options.Options) (options.Options, error) {
	if o == nil {
		return nil, nil
	}

	key := op.Key()
	v, ok := o[key]
	if !ok || v == nil {
		return o, nil
	}

	// v should be a string
	switch x := v.(type) {
	case string:
	// continue below
	case int:
		v = slog.Level(x)
		// continue below
	case slog.Level:
		return o, nil
	default:
		return nil, errz.Errorf("option {%s} should be {%T} or {%T} but got {%T}: %v",
			key, slog.LevelDebug, "", x, x)
	}

	var s string
	s, ok = v.(string)
	if !ok {
		return nil, errz.Errorf("option {%s} should be {%T} but got {%T}: %v",
			key, s, v, v)
	}

	var lvl slog.Level
	if err := lvl.UnmarshalText([]byte(s)); err != nil {
		return nil, errz.Wrapf(err, "option {%s} is not a valid {%T}", key, lvl)
	}

	o = o.Clone()
	o[key] = lvl
	return o, nil
}

// Get returns op's value in o. If o is nil, or no value
// is set, op's default value is returned.
func (op LogLevelOpt) Get(o options.Options) slog.Level {
	if o == nil {
		return op.defaultVal
	}

	v, ok := o[op.Key()]
	if !ok {
		return op.defaultVal
	}

	var lvl slog.Level
	lvl, ok = v.(slog.Level)
	if !ok {
		return op.defaultVal
	}

	return lvl
}

// GetAny implements options.Opt.
func (op LogLevelOpt) GetAny(o options.Options) any {
	return op.Get(o)
}

// DefaultAny implements options.Opt.
func (op LogLevelOpt) DefaultAny() any {
	return op.defaultVal
}