// Copyright 2020-2024 the Pinniped contributors. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0

// Package plog implements a thin layer over logr to help enforce pinniped's logging convention.
// Logs are always structured as a constant message with key and value pairs of related metadata.
//
// The logging levels in order of increasing verbosity are:
// error, warning, info, debug, trace and all.
//
// error and warning logs are always emitted (there is no way for the end user to disable them),
// and thus should be used sparingly.  Ideally, logs at these levels should be actionable.
//
// info should be reserved for "nice to know" information.  It should be possible to run a production
// pinniped server at the info log level with no performance degradation due to high log volume.
//
// debug should be used for information targeted at developers and to aid in support cases.  Care must
// be taken at this level to not leak any secrets into the log stream.  That is, even though debug may
// cause performance issues in production, it must not cause security issues in production.
//
// trace should be used to log information related to timing (i.e. the time it took a controller to sync).
// Just like debug, trace should not leak secrets into the log stream.  trace will likely leak information
// about the current state of the process, but that, along with performance degradation, is expected.
//
// all is reserved for the most verbose and security sensitive information.  At this level, full request
// metadata such as headers and parameters along with the body may be logged.  This level is completely
// unfit for production use both from a performance and security standpoint.  Using it is generally an
// act of desperation to determine why the system is broken.
package plog

import (
	"os"
	"slices"

	"github.com/go-logr/logr"
)

const errorKey = "error" // this matches zapr's default for .Error calls (which is asserted via tests)

// Logger implements the plog logging convention described above.  The global functions in this package
// such as Info should be used when one does not intend to write tests assertions for specific log messages.
// If test assertions are desired, Logger should be passed in as an input.  New should be used as the
// production implementation and TestLogger should be used to write test assertions.
type Logger interface {
	Error(msg string, err error, keysAndValues ...any)
	Warning(msg string, keysAndValues ...any)
	WarningErr(msg string, err error, keysAndValues ...any)
	Info(msg string, keysAndValues ...any)
	InfoErr(msg string, err error, keysAndValues ...any)
	Debug(msg string, keysAndValues ...any)
	DebugErr(msg string, err error, keysAndValues ...any)
	Trace(msg string, keysAndValues ...any)
	TraceErr(msg string, err error, keysAndValues ...any)
	All(msg string, keysAndValues ...any)
	Always(msg string, keysAndValues ...any)
	WithValues(keysAndValues ...any) Logger
	WithName(name string) Logger

	// does not include Fatal on purpose because that is not a method you should be using

	// for internal and test use only
	withDepth(d int) Logger
	withLogrMod(mod func(logr.Logger) logr.Logger) Logger
}

// MinLogger is the overlap between Logger and logr.Logger.
type MinLogger interface {
	Info(msg string, keysAndValues ...any)
}

var _ Logger = pLogger{}
var _, _, _ MinLogger = pLogger{}, logr.Logger{}, Logger(nil)

type pLogger struct {
	mods  []func(logr.Logger) logr.Logger
	depth int
}

func New() Logger {
	return pLogger{}
}

func (p pLogger) Error(msg string, err error, keysAndValues ...any) {
	p.logr().WithCallDepth(p.depth+1).Error(err, msg, keysAndValues...)
}

func (p pLogger) warningDepth(msg string, depth int, keysAndValues ...any) {
	if p.logr().V(klogLevelWarning).Enabled() {
		// klog's structured logging has no concept of a warning (i.e. no WarningS function)
		// Thus we use info at log level zero as a proxy
		// klog's info logs have an I prefix and its warning logs have a W prefix
		// Since we lose the W prefix by using InfoS, just add a key to make these easier to find
		keysAndValues = slices.Concat([]any{"warning", true}, keysAndValues)
		p.logr().V(klogLevelWarning).WithCallDepth(depth+1).Info(msg, keysAndValues...)
	}
}

func (p pLogger) Warning(msg string, keysAndValues ...any) {
	p.warningDepth(msg, p.depth+1, keysAndValues...)
}

func (p pLogger) WarningErr(msg string, err error, keysAndValues ...any) {
	p.warningDepth(msg, p.depth+1, slices.Concat([]any{errorKey, err}, keysAndValues)...)
}

func (p pLogger) infoDepth(msg string, depth int, keysAndValues ...any) {
	if p.logr().V(KlogLevelInfo).Enabled() {
		p.logr().V(KlogLevelInfo).WithCallDepth(depth+1).Info(msg, keysAndValues...)
	}
}

func (p pLogger) Info(msg string, keysAndValues ...any) {
	p.infoDepth(msg, p.depth+1, keysAndValues...)
}

func (p pLogger) InfoErr(msg string, err error, keysAndValues ...any) {
	p.infoDepth(msg, p.depth+1, slices.Concat([]any{errorKey, err}, keysAndValues)...)
}

func (p pLogger) debugDepth(msg string, depth int, keysAndValues ...any) {
	if p.logr().V(KlogLevelDebug).Enabled() {
		p.logr().V(KlogLevelDebug).WithCallDepth(depth+1).Info(msg, keysAndValues...)
	}
}

func (p pLogger) Debug(msg string, keysAndValues ...any) {
	p.debugDepth(msg, p.depth+1, keysAndValues...)
}

func (p pLogger) DebugErr(msg string, err error, keysAndValues ...any) {
	p.debugDepth(msg, p.depth+1, slices.Concat([]any{errorKey, err}, keysAndValues)...)
}

func (p pLogger) traceDepth(msg string, depth int, keysAndValues ...any) {
	if p.logr().V(KlogLevelTrace).Enabled() {
		p.logr().V(KlogLevelTrace).WithCallDepth(depth+1).Info(msg, keysAndValues...)
	}
}

func (p pLogger) Trace(msg string, keysAndValues ...any) {
	p.traceDepth(msg, p.depth+1, keysAndValues...)
}

func (p pLogger) TraceErr(msg string, err error, keysAndValues ...any) {
	p.traceDepth(msg, p.depth+1, slices.Concat([]any{errorKey, err}, keysAndValues)...)
}

func (p pLogger) All(msg string, keysAndValues ...any) {
	if p.logr().V(klogLevelAll).Enabled() {
		p.logr().V(klogLevelAll).WithCallDepth(p.depth+1).Info(msg, keysAndValues...)
	}
}

func (p pLogger) Always(msg string, keysAndValues ...any) {
	p.logr().WithCallDepth(p.depth+1).Info(msg, keysAndValues...)
}

func (p pLogger) WithValues(keysAndValues ...any) Logger {
	if len(keysAndValues) == 0 {
		return p
	}

	return p.withLogrMod(func(l logr.Logger) logr.Logger {
		return l.WithValues(keysAndValues...)
	})
}

func (p pLogger) WithName(name string) Logger {
	if len(name) == 0 {
		return p
	}

	return p.withLogrMod(func(l logr.Logger) logr.Logger {
		return l.WithName(name)
	})
}

func (p pLogger) withDepth(d int) Logger {
	out := p
	out.depth += d // out is a copy so this does not mutate p
	return out
}

func (p pLogger) withLogrMod(mod func(logr.Logger) logr.Logger) Logger {
	out := p // make a copy and carefully avoid mutating the mods slice
	mods := make([]func(logr.Logger) logr.Logger, 0, len(out.mods)+1)
	mods = slices.Concat(mods, out.mods)
	mods = append(mods, mod)
	out.mods = mods
	return out
}

func (p pLogger) logr() logr.Logger {
	l := globalLogger // grab the current global logger and its current config
	for _, mod := range p.mods {
		l = mod(l) // and then update it with all modifications
	}
	return l // this logger is guaranteed to have the latest config and all modifications
}

var logger = New().withDepth(1) //nolint:gochecknoglobals

func Error(msg string, err error, keysAndValues ...any) {
	logger.Error(msg, err, keysAndValues...)
}

func Warning(msg string, keysAndValues ...any) {
	logger.Warning(msg, keysAndValues...)
}

func WarningErr(msg string, err error, keysAndValues ...any) {
	logger.WarningErr(msg, err, keysAndValues...)
}

func Info(msg string, keysAndValues ...any) {
	logger.Info(msg, keysAndValues...)
}

func InfoErr(msg string, err error, keysAndValues ...any) {
	logger.InfoErr(msg, err, keysAndValues...)
}

func Debug(msg string, keysAndValues ...any) {
	logger.Debug(msg, keysAndValues...)
}

func DebugErr(msg string, err error, keysAndValues ...any) {
	logger.DebugErr(msg, err, keysAndValues...)
}

func Trace(msg string, keysAndValues ...any) {
	logger.Trace(msg, keysAndValues...)
}

func TraceErr(msg string, err error, keysAndValues ...any) {
	logger.TraceErr(msg, err, keysAndValues...)
}

func All(msg string, keysAndValues ...any) {
	logger.All(msg, keysAndValues...)
}

func Always(msg string, keysAndValues ...any) {
	logger.Always(msg, keysAndValues...)
}

func WithValues(keysAndValues ...any) Logger {
	// this looks weird but it is the same as New().WithValues(keysAndValues...) because it returns a new logger rooted at the call site
	return logger.withDepth(-1).WithValues(keysAndValues...)
}

func WithName(name string) Logger {
	// this looks weird but it is the same as New().WithName(name) because it returns a new logger rooted at the call site
	return logger.withDepth(-1).WithName(name)
}

func Fatal(err error, keysAndValues ...any) {
	logger.Error("unrecoverable error encountered", err, keysAndValues...)
	globalFlush()
	os.Exit(1)
}
