// Copyright (c) 2026 Storm Dragon
// SPDX-License-Identifier: GPL-3.0-or-later

package sound

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"math"
	"sync"
	"sync/atomic"
	"time"

	"git.stormux.org/storm/fenrir/internal/audio"
	"git.stormux.org/storm/fenrir/internal/presentation"
)

type soundBackend interface {
	Play(presentation.Cue) bool
	Play_wait(context.Context, presentation.Cue) error
	Play_progress(float64) bool
	Play_indentation(int) bool
	Discard_progress()
	Clear_progress()
	Set_volume(float64)
	Errors() <-chan error
	Finish(context.Context) error
	Close()
}

type soundConnection struct{ backend soundBackend }

var errSoundAttemptStalled = errors.New("sound driver open did not return before its deadline")

// Player keeps connection work away from cue admission and keyboard handling.
// Missing output rejects cues so the caller can present their speech equivalent.
type Player struct {
	connection atomic.Pointer[soundConnection]
	volume     atomic.Uint64
	cancel     context.CancelFunc
	done       chan struct{}
	errors     chan error
	once       sync.Once
}

func Open_recovering(ctx context.Context, roots []string, options Options) *Player {
	return new_player(ctx, options.Volume, func() (soundBackend, error) {
		service, err := Open(roots, options)
		if service == nil {
			return nil, err
		}
		if err != nil {
			slog.Warn("sound unavailable or incomplete", "error", err, "at", time.Now())
		}
		return service, nil
	})
}

func new_player(ctx context.Context, volume float64, open func() (soundBackend, error)) *Player {
	ctx, cancel := context.WithCancel(ctx)
	p := &Player{cancel: cancel, done: make(chan struct{}), errors: make(chan error, 1)}
	p.volume.Store(math.Float64bits(volume))
	// Even a driver whose connection or stream-start call ignores cancellation
	// cannot hold startup forever. Never retry an attempt that is still stuck.
	backend, err := sound_attempt(ctx, open)
	if err == nil {
		p.connection.Store(&soundConnection{backend})
		backend.Set_volume(volume)
	} else {
		slog.Warn("sound unavailable or incomplete", "reconnecting", true, "error", err, "at", time.Now())
	}
	go p.run(ctx, open, err)
	return p
}

// A timed-out native/library call is quarantined once. A late result is closed
// by its own worker; no further opener goroutines are started for this player.
func sound_attempt(ctx context.Context, open func() (soundBackend, error)) (soundBackend, error) {
	ctx, cancel := context.WithTimeout(ctx, 3*time.Second)
	defer cancel()
	type result struct {
		backend soundBackend
		err     error
	}
	results := make(chan result)
	go func() {
		backend, err := open()
		select {
		case results <- result{backend, err}:
		case <-ctx.Done():
			if backend != nil {
				backend.Close()
			}
		}
	}()
	select {
	case result := <-results:
		return result.backend, result.err
	case <-ctx.Done():
		return nil, errors.Join(errSoundAttemptStalled, ctx.Err())
	}
}

func (p *Player) run(ctx context.Context, open func() (soundBackend, error), initialError error) {
	defer close(p.done)
	problem := initialError
	for {
		connection := p.connection.Load()
		if connection == nil {
			if errors.Is(problem, errSoundAttemptStalled) || errors.Is(problem, context.Canceled) {
				if ctx.Err() == nil {
					p.errors <- fmt.Errorf("sound initialization timed out: %w", problem)
				}
				return
			}
			retryContext, cancel := context.WithTimeout(ctx, audio.RecoveryTimeout)
			var backend soundBackend
			err := audio.Retry(retryContext, func(ctx context.Context) error {
				var err error
				backend, err = sound_attempt(ctx, open)
				return err
			}, func(err error) bool {
				return !errors.Is(err, errSoundAttemptStalled) && !errors.Is(err, context.Canceled)
			})
			cancel()
			if err != nil {
				if ctx.Err() == nil {
					p.errors <- fmt.Errorf("sound recovery failed: %w", err)
				}
				return
			}
			connection = &soundConnection{backend}
			p.connection.Store(connection)
			backend.Set_volume(math.Float64frombits(p.volume.Load()))
			slog.Info("sound connection restored", "at", time.Now())
		}
		select {
		case <-ctx.Done():
			return
		case problem = <-connection.backend.Errors():
			p.connection.Store(nil)
			connection.backend.Close()
			slog.Warn("sound connection lost; reconnecting", "error", problem, "at", time.Now())
		}
	}
}

func (p *Player) Errors() <-chan error { return p.errors }

func (p *Player) Available() bool { return p.connection.Load() != nil }

func (p *Player) Play(cue presentation.Cue) bool {
	if connection := p.connection.Load(); connection != nil {
		return connection.backend.Play(cue)
	}
	return false
}

func (p *Player) Play_wait(ctx context.Context, cue presentation.Cue) error {
	if connection := p.connection.Load(); connection != nil {
		return connection.backend.Play_wait(ctx, cue)
	}
	return nil
}

func (p *Player) Play_progress(value float64) bool {
	if connection := p.connection.Load(); connection != nil {
		return connection.backend.Play_progress(value)
	}
	return false
}

func (p *Player) Play_indentation(level int) bool {
	if connection := p.connection.Load(); connection != nil {
		return connection.backend.Play_indentation(level)
	}
	return false
}

func (p *Player) Discard_progress() {
	if connection := p.connection.Load(); connection != nil {
		connection.backend.Discard_progress()
	}
}

func (p *Player) Clear_progress() {
	if connection := p.connection.Load(); connection != nil {
		connection.backend.Clear_progress()
	}
}

func (p *Player) Set_volume(volume float64) {
	p.volume.Store(math.Float64bits(volume))
	if connection := p.connection.Load(); connection != nil {
		connection.backend.Set_volume(volume)
	}
}

func (p *Player) Finish(ctx context.Context) error {
	p.cancel()
	<-p.done
	if connection := p.connection.Load(); connection != nil {
		return connection.backend.Finish(ctx)
	}
	return nil
}

func (p *Player) Close() {
	p.once.Do(func() {
		p.cancel()
		<-p.done
		if connection := p.connection.Swap(nil); connection != nil {
			connection.backend.Close()
		}
	})
}