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

package app

import (
	"bufio"
	"context"
	"encoding/json"
	"errors"
	"io"
	"log/slog"
	"os"
	"os/exec"
	"strings"
	"time"

	"git.stormux.org/storm/cthulhu/internal/clipboard"
	"git.stormux.org/storm/cthulhu/internal/config"
	"git.stormux.org/storm/cthulhu/internal/platform/session"
)

type clipboardScope struct {
	settings               *config.Settings
	application, requested string
	enabled                bool
}

func clipboard_scope(live *liveSettings, gate *focusGate) clipboardScope {
	scope := clipboardScope{settings: live.current.Load()}
	if name := live.application.Load(); name != nil {
		scope.application = *name
	}
	if name := live.requestedApplication.Load(); name != nil {
		scope.requested = *name
	}
	scope.enabled = scope.settings.Reading.AutomaticallyReadClipboardChanges && !gate.Locked() && !gate.Suspended() &&
		(scope.requested == "" || scope.requested == scope.application)
	return scope
}

func run_automatic_clipboard(ctx context.Context, logger *slog.Logger, live *liveSettings, gate *focusGate, speech speechEnqueuer) <-chan struct{} {
	done := make(chan struct{})
	go func() {
		defer close(done)
		if live == nil {
			return
		}
		// No helper or clipboard reads until an application enables the feature.
		ticker := time.NewTicker(20 * time.Millisecond)
		defer ticker.Stop()
		for !clipboard_scope(live, gate).enabled {
			select {
			case <-ctx.Done():
				return
			case <-live.clipboardChanges:
			case <-ticker.C:
			}
		}
		ticker.Stop()
		if err := watch_clipboard(ctx, live, gate, speech); err != nil && ctx.Err() == nil {
			logger.Warn("automatic clipboard reading unavailable", "error", err)
		}
	}()
	return done
}

func watch_clipboard(ctx context.Context, live *liveSettings, gate *focusGate, speech speechEnqueuer) error {
	executable, err := os.Executable()
	if err != nil {
		return err
	}
	childCtx, cancel := context.WithCancel(ctx)
	defer cancel()
	command := exec.CommandContext(childCtx, executable, "--clipboard-watch")
	command.Env = session.GTKEnvironment()
	command.WaitDelay = time.Second
	in, err := command.StdinPipe()
	if err != nil {
		return err
	}
	defer in.Close()
	out, err := command.StdoutPipe()
	if err != nil {
		return err
	}
	defer out.Close()
	var diagnostic preferencesStderr
	command.Stderr = &diagnostic
	if err := command.Start(); err != nil {
		return err
	}
	defer func() { cancel(); in.Close(); out.Close(); command.Wait() }()
	changes := make(chan clipboard.TextChange, 128)
	failures := make(chan error, 1)
	readerDone := make(chan struct{})
	go func() {
		defer close(readerDone)
		scanner := bufio.NewScanner(out)
		scanner.Buffer(make([]byte, 4096), 1024*1024)
		for scanner.Scan() {
			var change clipboard.TextChange
			if err := json.Unmarshal(scanner.Bytes(), &change); err != nil {
				failures <- err
				return
			}
			select {
			case changes <- change:
			case <-childCtx.Done():
				return
			}
		}
		err := scanner.Err()
		if err == nil {
			err = io.EOF
		}
		failures <- err
	}()
	defer func() { cancel(); out.Close(); <-readerDone }()
	return serve_clipboard_changes(ctx, live, gate, speech, json.NewEncoder(in), changes, failures)
}

func serve_clipboard_changes(ctx context.Context, live *liveSettings, gate *focusGate, speech speechEnqueuer, encoder *json.Encoder, changes <-chan clipboard.TextChange, failures <-chan error) error {
	ticker := time.NewTicker(20 * time.Millisecond)
	defer ticker.Stop()
	var previous clipboardScope
	var epoch uint64
	var lastText string
	update := func() error {
		scope := clipboard_scope(live, gate)
		if scope == previous {
			return nil
		}
		previous = scope
		epoch++
		lastText = ""
		return encoder.Encode(clipboard.WatchSettings{Enabled: scope.enabled, Epoch: epoch})
	}
	if err := update(); err != nil {
		return err
	}
	for {
		select {
		case <-ctx.Done():
			return ctx.Err()
		case err := <-failures:
			return err
		case <-live.clipboardChanges:
			if err := update(); err != nil {
				return err
			}
		case <-ticker.C:
			// Check the screen-lock gate without polling clipboard contents.
			if err := update(); err != nil {
				return err
			}
		case change, ok := <-changes:
			if !ok {
				return errors.New("clipboard helper closed")
			}
			if change.Ready {
				continue
			}
			if clipboard_scope(live, gate) != previous {
				if err := update(); err != nil {
					return err
				}
			}
			if !previous.enabled || change.Epoch != epoch {
				continue
			}
			if strings.TrimSpace(change.Text) != "" && change.Text != lastText {
				speech.Enqueue(speechRequest{Text: change.Text, Role: "system", Cause: "clipboard", Append: true, ClipboardTimestamp: change.Timestamp})
			}
			lastText = change.Text
		}
	}
}