package api

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"os"
	"os/exec"
	"strings"
	"syscall"
	"time"

	"github.com/alexliesenfeld/health"
	flag "github.com/spf13/pflag"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/codes"
	"go.opentelemetry.io/otel/metric"
	"go.uber.org/multierr"

	"github.com/gotenberg/gotenberg/v8/pkg/gotenberg"
	"github.com/gotenberg/gotenberg/v8/pkg/modules/api"
)

func init() {
	gotenberg.MustRegisterModule(new(Api))
}

var (
	// ErrInvalidPdfFormats happens if LibreOffice cannot handle the PDF
	// formats option.
	ErrInvalidPdfFormats = errors.New("invalid PDF formats")

	// ErrUnoException happens when unoconverter returns exit code 5.
	ErrUnoException = errors.New("uno exception")

	// ErrRuntimeException happens when unoconverter returns exit code 6.
	ErrRuntimeException = errors.New("uno exception")

	// ErrCoreDumped happens randomly; sometimes a conversion will work as
	// expected, and some other time the same conversion will fail.
	// See https://github.com/gotenberg/gotenberg/issues/639.
	ErrCoreDumped = errors.New("core dumped")
)

// Api is a module that provides a [Uno] to interact with LibreOffice.
type Api struct {
	autoStart bool
	args      libreOfficeArguments

	logger      *slog.Logger
	libreOffice libreOffice
	supervisor  gotenberg.ProcessSupervisor

	reqsCounter               metric.Int64Counter
	errsCounter               metric.Int64Counter
	conversionDurationCounter metric.Float64Histogram
	queueWaitDurationCounter  metric.Float64Histogram
	pdfOutputSizeCounter      metric.Int64Histogram
}

// Options gathers available options when converting a document to PDF.
// See: https://help.libreoffice.org/latest/en-US/text/shared/guide/pdf_params.html.
type Options struct {
	// Password specifies the password for opening the source file.
	Password string // #nosec

	// Landscape allows changing the orientation of the resulting PDF.
	Landscape bool

	// PageRanges allows selecting the pages to convert.
	PageRanges string

	// UpdateIndexes specifies whether to update the indexes before conversion,
	// keeping in mind that doing so might result in missing links in the final
	// PDF.
	UpdateIndexes bool

	// ExportFormFields specifies whether form fields are exported as widgets
	// or only their fixed print representation is exported.
	ExportFormFields bool

	// AllowDuplicateFieldNames specifies whether multiple form fields exported
	// are allowed to have the same field name.
	AllowDuplicateFieldNames bool

	// ExportBookmarks specifies if bookmarks are exported to PDF.
	ExportBookmarks bool

	// ExportBookmarksToPdfDestination specifies that the bookmarks contained
	// in the source LibreOffice file should be exported to the PDF file as
	// Named Destination.
	ExportBookmarksToPdfDestination bool

	// ExportPlaceholders exports the placeholder fields visual markings only.
	// The exported placeholder is ineffective.
	ExportPlaceholders bool

	// ExportNotes specifies if notes are exported to PDF.
	ExportNotes bool

	// ExportNotesPages specifies if notes pages are exported to PDF.
	// Notes pages are available in Impress documents only.
	ExportNotesPages bool

	// ExportOnlyNotesPages specifies if the property ExportNotesPages is set
	// to true if only notes pages are exported to PDF.
	ExportOnlyNotesPages bool

	// ExportNotesInMargin specifies if notes in the margin are exported to
	// PDF.
	ExportNotesInMargin bool

	// ConvertOooTargetToPdfTarget specifies that the target documents with
	// .od[tpgs] extension will have that extension changed to .pdf when the
	// link is exported to PDF. The source document remains untouched.
	ConvertOooTargetToPdfTarget bool

	// ExportLinksRelativeFsys specifies that the file system related
	// hyperlinks (file:// protocol) present in the document will be exported
	// as relative to the source document location.
	ExportLinksRelativeFsys bool

	// ExportHiddenSlides exports, for LibreOffice Impress, slides that are not
	// included in slide shows.
	ExportHiddenSlides bool

	// SkipEmptyPages specifies that automatically inserted empty pages are
	// suppressed. This option is active only if storing Writer documents.
	SkipEmptyPages bool

	// AddOriginalDocumentAsStream specifies that a stream is inserted to the
	// PDF file which contains the original document for archiving purposes.
	AddOriginalDocumentAsStream bool

	// SinglePageSheets ignores each sheet’s paper size, print ranges and
	// shown/hidden status and puts every sheet (even hidden sheets) on exactly
	// one page.
	SinglePageSheets bool

	// LosslessImageCompression specifies if images are exported to PDF using
	// a lossless compression format like PNG or compressed using the JPEG
	// format.
	LosslessImageCompression bool

	// Quality specifies the quality of the JPG export. A higher value produces
	// a higher-quality image and a larger file. Between 1 and 100.
	Quality int

	// ReduceImageResolution specifies if the resolution of each image is
	// reduced to the resolution specified by the property MaxImageResolution.
	ReduceImageResolution bool

	// MaxImageResolution, if the property ReduceImageResolution is set to
	// true, tells if all images will be reduced to the given value in DPI.
	// Possible values are: 75, 150, 300, 600 and 1200.
	MaxImageResolution int

	// PdfFormats allows to convert the resulting PDF to PDF/A-1b, PDF/A-2b,
	// PDF/A-3b and PDF/UA.
	PdfFormats gotenberg.PdfFormats
}

// DefaultOptions returns the default values for Options.
func DefaultOptions() Options {
	return Options{
		Password:                        "",
		Landscape:                       false,
		PageRanges:                      "",
		UpdateIndexes:                   true,
		ExportFormFields:                true,
		AllowDuplicateFieldNames:        false,
		ExportBookmarks:                 true,
		ExportBookmarksToPdfDestination: false,
		ExportPlaceholders:              false,
		ExportNotes:                     false,
		ExportNotesPages:                false,
		ExportOnlyNotesPages:            false,
		ExportNotesInMargin:             false,
		ConvertOooTargetToPdfTarget:     false,
		ExportLinksRelativeFsys:         false,
		ExportHiddenSlides:              false,
		SkipEmptyPages:                  false,
		AddOriginalDocumentAsStream:     false,
		SinglePageSheets:                false,
		LosslessImageCompression:        false,
		Quality:                         90,
		ReduceImageResolution:           false,
		MaxImageResolution:              300,
		PdfFormats: gotenberg.PdfFormats{
			PdfA:  "",
			PdfUa: false,
		},
	}
}

// Uno is an abstraction on top of the Universal Network Objects API.
type Uno interface {
	Pdf(ctx context.Context, logger *slog.Logger, inputPath, outputPath string, options Options) error
	Extensions() []string
}

// Provider is a module interface that exposes a method for creating a
// [Uno] for other modules.
//
//	func (m *YourModule) Provision(ctx *gotenberg.Context) error {
//		provider, _ := ctx.Module(new(libreofficeapi.Provider))
//		libreOffice, _      := provider.(api.Provider).LibreOffice()
//	}
type Provider interface {
	LibreOffice() (Uno, error)
}

// Descriptor returns a [Api]'s module descriptor.
func (a *Api) Descriptor() gotenberg.ModuleDescriptor {
	return gotenberg.ModuleDescriptor{
		ID: "libreoffice-api",
		FlagSet: func() *flag.FlagSet {
			fs := flag.NewFlagSet("api", flag.ExitOnError)
			fs.Int64("libreoffice-restart-after", 10, "Number of conversions after which LibreOffice will automatically restart. Set to 0 to disable this feature")
			fs.Int64("libreoffice-max-queue-size", 0, "Maximum request queue size for LibreOffice. Set to 0 to disable this feature")
			fs.Bool("libreoffice-auto-start", false, "Automatically launch LibreOffice upon initialization if set to true; otherwise, LibreOffice will start at the time of the first conversion")
			fs.Duration("libreoffice-start-timeout", time.Duration(20)*time.Second, "Maximum duration to wait for LibreOffice to start or restart")

			return fs
		}(),
		New: func() gotenberg.Module { return new(Api) },
	}
}

// Provision sets the module properties.
func (a *Api) Provision(ctx *gotenberg.Context) error {
	flags := ctx.ParsedFlags()
	a.autoStart = flags.MustBool("libreoffice-auto-start")

	libreOfficeBinPath, ok := os.LookupEnv("LIBREOFFICE_BIN_PATH")
	if !ok {
		return errors.New("LIBREOFFICE_BIN_PATH environment variable is not set")
	}

	unoBinPath, ok := os.LookupEnv("UNOCONVERTER_BIN_PATH")
	if !ok {
		return errors.New("UNOCONVERTER_BIN_PATH environment variable is not set")
	}

	a.args = libreOfficeArguments{
		binPath:      libreOfficeBinPath,
		unoBinPath:   unoBinPath,
		startTimeout: flags.MustDuration("libreoffice-start-timeout"),
	}

	// Logger.
	a.logger = gotenberg.Logger(a).With(slog.String("logger", "libreoffice"))

	// Process.
	a.libreOffice = newLibreOfficeProcess(a.args)
	a.supervisor = gotenberg.NewProcessSupervisor(a.logger, a.libreOffice, flags.MustInt64("libreoffice-restart-after"), flags.MustInt64("libreoffice-max-queue-size"), 1)

	// OpenTelemetry.
	meter := gotenberg.Meter()
	_, err := meter.Int64ObservableCounter(
		"libreoffice.process.restarts.total",
		metric.WithDescription("Current number of LibreOffice restarts."),
		metric.WithUnit("{restart}"),
		metric.WithInt64Callback(func(_ context.Context, o metric.Int64Observer) error {
			val := a.supervisor.RestartsCount()
			o.Observe(val)
			return nil
		}),
	)
	if err != nil {
		return fmt.Errorf("create process restarts observable counter: %w", err)
	}

	_, err = meter.Int64ObservableGauge(
		"libreoffice.requests.queue_size",
		metric.WithDescription("Current number of LibreOffice conversion requests waiting to be treated."),
		metric.WithUnit("{request}"),
		metric.WithInt64Callback(func(_ context.Context, o metric.Int64Observer) error {
			val := a.supervisor.ReqQueueSize()
			o.Observe(val)
			return nil
		}),
	)
	if err != nil {
		return fmt.Errorf("create requests queue size observable gauge: %w", err)
	}

	_, err = meter.Int64ObservableGauge(
		"libreoffice.requests.active",
		metric.WithDescription("Current number of LibreOffice conversion requests actively being processed."),
		metric.WithUnit("{request}"),
		metric.WithInt64Callback(func(_ context.Context, o metric.Int64Observer) error {
			val := a.supervisor.ActiveTasksCount()
			o.Observe(val)
			return nil
		}),
	)
	if err != nil {
		return fmt.Errorf("create requests active observable gauge: %w", err)
	}

	a.reqsCounter, err = meter.Int64Counter(
		"libreoffice.requests.total",
		metric.WithDescription("Total number of LibreOffice conversion requests."),
		metric.WithUnit("{request}"),
	)
	if err != nil {
		return fmt.Errorf("create requests total counter: %w", err)
	}

	a.errsCounter, err = meter.Int64Counter(
		"libreoffice.errors.total",
		metric.WithDescription("Total number of LibreOffice errors."),
		metric.WithUnit("{error}"),
	)
	if err != nil {
		return fmt.Errorf("create errors total counter: %w", err)
	}

	a.conversionDurationCounter, err = meter.Float64Histogram(
		"libreoffice.conversion.duration",
		metric.WithDescription("Duration of each PDF conversion."),
		metric.WithUnit("s"),
		metric.WithExplicitBucketBoundaries(0.5, 1, 2, 5, 10, 30, 60),
	)
	if err != nil {
		return fmt.Errorf("create conversion duration histogram: %w", err)
	}

	a.queueWaitDurationCounter, err = meter.Float64Histogram(
		"libreoffice.queue.wait.duration",
		metric.WithDescription("Time a request spends waiting in the queue before processing starts."),
		metric.WithUnit("s"),
		metric.WithExplicitBucketBoundaries(0.5, 1, 2, 5, 10, 30, 60),
	)
	if err != nil {
		return fmt.Errorf("create queue wait duration histogram: %w", err)
	}

	a.pdfOutputSizeCounter, err = meter.Int64Histogram(
		"libreoffice.pdf.output.size",
		metric.WithDescription("Size of the generated PDF files."),
		metric.WithUnit("By"),
	)
	if err != nil {
		return fmt.Errorf("create pdf output size histogram: %w", err)
	}

	return nil
}

// Validate validates the module properties.
func (a *Api) Validate() error {
	var err error

	_, statErr := os.Stat(a.args.binPath)
	if os.IsNotExist(statErr) {
		err = multierr.Append(err, fmt.Errorf("LibreOffice binary path does not exist: %w", statErr))
	}

	_, statErr = os.Stat(a.args.unoBinPath)
	if os.IsNotExist(statErr) {
		err = multierr.Append(err, fmt.Errorf("unoconverter binary path does not exist: %w", statErr))
	}

	return err
}

// Start does nothing if auto-start is not enabled. Otherwise, it starts a
// LibreOffice instance.
func (a *Api) Start() error {
	if !a.autoStart {
		return nil
	}

	err := a.supervisor.Launch()
	if err != nil {
		return fmt.Errorf("launch supervisor: %w", err)
	}

	return nil
}

// StartupMessage returns a custom startup message.
func (a *Api) StartupMessage() string {
	if !a.autoStart {
		return "LibreOffice ready to start"
	}

	return "LibreOffice automatically started"
}

// Stop stops the current browser instance.
func (a *Api) Stop(ctx context.Context) error {
	// Block until the context is done so that another module may gracefully
	// stop before we do a shutdown.
	a.logger.DebugContext(ctx, "wait for the end of grace duration")

	<-ctx.Done()

	err := a.supervisor.Shutdown()
	if err == nil {
		return nil
	}

	return fmt.Errorf("stop LibreOffice: %w", err)
}

// Debug returns additional debug data.
func (a *Api) Debug() map[string]any {
	debug := make(map[string]any)

	cmd := exec.Command(a.args.binPath, "--version") //nolint:gosec
	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}

	output, err := cmd.Output()
	if err != nil {
		debug["version"] = err.Error()
		return debug
	}

	debug["version"] = strings.TrimSpace(string(output))
	return debug
}

// Checks adds a health check that verifies if LibreOffice is healthy.
func (a *Api) Checks() ([]health.CheckerOption, error) {
	return []health.CheckerOption{
		health.WithCheck(health.Check{
			Name: "libreoffice",
			Check: func(_ context.Context) error {
				if a.supervisor.Healthy() {
					return nil
				}

				return errors.New("LibreOffice is unhealthy")
			},
		}),
	}, nil
}

// Ready returns no error if the module is ready.
func (a *Api) Ready() error {
	if !a.autoStart {
		return nil
	}

	ctx, cancel := context.WithTimeout(context.Background(), a.args.startTimeout)
	defer cancel()

	ticker := time.NewTicker(time.Duration(100) * time.Millisecond)

	for {
		select {
		case <-ctx.Done():
			ticker.Stop()
			return fmt.Errorf("context done while waiting for LibreOffice to be ready: %w", ctx.Err())
		case <-ticker.C:
			ok := a.libreOffice.Healthy(a.logger)
			if ok {
				ticker.Stop()
				return nil
			}

			continue
		}
	}
}

// LibreOffice returns a [Uno] for interacting with LibreOffice.
func (a *Api) LibreOffice() (Uno, error) {
	return a, nil
}

// Pdf converts a document to PDF.
func (a *Api) Pdf(ctx context.Context, logger *slog.Logger, inputPath, outputPath string, options Options) error {
	ctx, span := gotenberg.Tracer().Start(ctx, "LibreOffice.Pdf")
	defer span.End()

	start := time.Now()
	var conversionStart time.Time

	err := a.supervisor.Run(ctx, logger, func() error {
		conversionStart = time.Now()
		return a.libreOffice.pdf(ctx, logger, inputPath, outputPath, options)
	})

	end := time.Now()

	status := "success"
	if err != nil {
		if errors.Is(err, context.DeadlineExceeded) || errors.Is(err, context.Canceled) {
			status = "timeout"
		} else {
			status = "error"
		}
	}

	if !conversionStart.IsZero() {
		waitDuration := conversionStart.Sub(start).Seconds()
		conversionDuration := end.Sub(conversionStart).Seconds()

		a.queueWaitDurationCounter.Record(ctx, waitDuration, metric.WithAttributes(
			attribute.String("status", status),
		))
		a.conversionDurationCounter.Record(ctx, conversionDuration, metric.WithAttributes(
			attribute.String("status", status),
		))
	} else {
		waitDuration := end.Sub(start).Seconds()
		a.queueWaitDurationCounter.Record(ctx, waitDuration, metric.WithAttributes(
			attribute.String("status", status),
		))
	}

	a.reqsCounter.Add(ctx, 1, metric.WithAttributes(
		attribute.String("status", status),
	))

	if err == nil {
		if fileInfo, statErr := os.Stat(outputPath); statErr == nil {
			a.pdfOutputSizeCounter.Record(ctx, fileInfo.Size())
		}
		return nil
	}

	reason := "unknown"
	if errors.Is(err, context.DeadlineExceeded) {
		reason = "timeout"
	} else if errors.Is(err, context.Canceled) {
		reason = "context_cancelled"
	} else if errors.Is(err, ErrInvalidPdfFormats) {
		reason = "invalid_input"
	} else if errors.Is(err, gotenberg.ErrMaximumQueueSizeExceeded) {
		reason = "libreoffice_maximum_queue_size_exceeded"
	} else if errors.Is(err, gotenberg.ErrProcessAlreadyRestarting) {
		reason = "libreoffice_unavailable"
	}

	a.errsCounter.Add(ctx, 1, metric.WithAttributes(
		attribute.String("reason", reason),
	))

	// See https://github.com/gotenberg/gotenberg/issues/639.
	if errors.Is(err, ErrCoreDumped) {
		logger.DebugContext(ctx, fmt.Sprintf("got a '%s' error, retry conversion", err))
		err = a.Pdf(ctx, logger, inputPath, outputPath, options)
		if err != nil {
			span.RecordError(err)
			span.SetStatus(codes.Error, err.Error())
		}
		return err
	}

	err = fmt.Errorf("supervisor run task: %w", err)
	span.RecordError(err)
	span.SetStatus(codes.Error, err.Error())

	return err
}

// Extensions returns the file extensions available for conversions.
// FIXME: don't care, take all on the route level?
func (a *Api) Extensions() []string {
	return []string{
		".123",
		".602",
		".abw",
		".bib",
		".bmp",
		".cdr",
		".cgm",
		".cmx",
		".csv",
		".cwk",
		".dbf",
		".dif",
		".doc",
		".docm",
		".docx",
		".dot",
		".dotm",
		".dotx",
		".dxf",
		".emf",
		".eps",
		".epub",
		".fodg",
		".fodp",
		".fods",
		".fodt",
		".fopd",
		".gif",
		".htm",
		".html",
		".hwp",
		".jpeg",
		".jpg",
		".key",
		".ltx",
		".lwp",
		".mcw",
		".met",
		".mml",
		".mw",
		".numbers",
		".odd",
		".odg",
		".odm",
		".odp",
		".ods",
		".odt",
		".otg",
		".oth",
		".otp",
		".ots",
		".ott",
		".pages",
		".pbm",
		".pcd",
		".pct",
		".pcx",
		".pdb",
		".pdf",
		".pgm",
		".png",
		".pot",
		".potm",
		".potx",
		".ppm",
		".pps",
		".ppt",
		".pptm",
		".pptx",
		".psd",
		".psw",
		".pub",
		".pwp",
		".pxl",
		".ras",
		".rtf",
		".sda",
		".sdc",
		".sdd",
		".sdp",
		".sdw",
		".sgl",
		".slk",
		".smf",
		".stc",
		".std",
		".sti",
		".stw",
		".svg",
		".svm",
		".swf",
		".sxc",
		".sxd",
		".sxg",
		".sxi",
		".sxm",
		".sxw",
		".tga",
		".tif",
		".tiff",
		".txt",
		".uof",
		".uop",
		".uos",
		".uot",
		".vdx",
		".vor",
		".vsd",
		".vsdm",
		".vsdx",
		".wb2",
		".wk1",
		".wks",
		".wmf",
		".wpd",
		".wpg",
		".wps",
		".xbm",
		".xhtml",
		".xls",
		".xlsb",
		".xlsm",
		".xlsx",
		".xlt",
		".xltm",
		".xltx",
		".xlw",
		".xml",
		".xpm",
		".zabw",
	}
}

// Interface guards.
var (
	_ gotenberg.Module      = (*Api)(nil)
	_ gotenberg.Provisioner = (*Api)(nil)
	_ gotenberg.Validator   = (*Api)(nil)
	_ gotenberg.App         = (*Api)(nil)
	_ gotenberg.Debuggable  = (*Api)(nil)
	_ api.HealthChecker     = (*Api)(nil)
	_ Uno                   = (*Api)(nil)
	_ Provider              = (*Api)(nil)
)