package printer

import (
	"context"
	"fmt"
	"os"
	"path/filepath"

	"github.com/thecodingmachine/gotenberg/internal/pkg/conf"
	"github.com/thecodingmachine/gotenberg/internal/pkg/xcontext"
	"github.com/thecodingmachine/gotenberg/internal/pkg/xerror"
	"github.com/thecodingmachine/gotenberg/internal/pkg/xexec"
	"github.com/thecodingmachine/gotenberg/internal/pkg/xlog"
	"github.com/thecodingmachine/gotenberg/internal/pkg/xrand"
)

type officePrinter struct {
	logger xlog.Logger
	fpaths []string
	opts   OfficePrinterOptions
}

// OfficePrinterOptions helps customizing the
// Office Printer behaviour.
type OfficePrinterOptions struct {
	WaitTimeout float64
	Landscape   bool
}

// DefaultOfficePrinterOptions returns the default
// Office Printer options.
func DefaultOfficePrinterOptions(config conf.Config) OfficePrinterOptions {
	return OfficePrinterOptions{
		WaitTimeout: config.DefaultWaitTimeout(),
		Landscape:   false,
	}
}

// NewOfficePrinter returns a Printer which
// is able to convert Office documents to PDF.
func NewOfficePrinter(logger xlog.Logger, fpaths []string, opts OfficePrinterOptions) Printer {
	return officePrinter{
		logger: logger,
		fpaths: fpaths,
		opts:   opts,
	}
}

func (p officePrinter) Print(destination string) error {
	const op string = "printer.officePrinter.Print"
	logOptions(p.logger, p.opts)
	ctx, cancel := xcontext.WithTimeout(p.logger, p.opts.WaitTimeout)
	defer cancel()
	resolver := func() error {
		fpaths := make([]string, len(p.fpaths))
		dirPath := filepath.Dir(destination)
		for i, fpath := range p.fpaths {
			baseFilename := xrand.Get()
			tmpDest := fmt.Sprintf("%s/%d%s.pdf", dirPath, i, baseFilename)
			p.logger.DebugfOp(op, "converting '%s' to PDF...", fpath)
			if err := unoconv(ctx, p.logger, fpath, tmpDest, p.opts); err != nil {
				return err
			}
			p.logger.DebugfOp(op, "'%s.pdf' created", baseFilename)
			fpaths[i] = tmpDest
		}
		if len(fpaths) == 1 {
			p.logger.DebugOp(op, "only one PDF created, nothing to merge")
			if err := os.Rename(fpaths[0], destination); err != nil {
				return err
			}
			return nil
		}
		m := mergePrinter{
			logger: p.logger,
			ctx:    ctx,
			fpaths: fpaths,
		}
		return m.Print(destination)
	}
	if err := resolver(); err != nil {
		return xcontext.MustHandleError(
			ctx,
			xerror.New(op, err),
		)
	}
	return nil
}

// nolint: gochecknoglobals
var lock = make(chan struct{}, 1)

func unoconv(ctx context.Context, logger xlog.Logger, fpath, destination string, opts OfficePrinterOptions) error {
	const op string = "printer.unoconv"
	resolver := func() error {
		args := []string{
			"--format",
			"pdf",
		}
		if opts.Landscape {
			args = append(args, "--printer", "PaperOrientation=landscape")
		}
		args = append(args, "--output", destination, fpath)
		cmd, err := xexec.CommandContext(
			ctx,
			logger,
			"unoconv",
			args...,
		)
		if err != nil {
			return err
		}
		xexec.LogBeforeExecute(logger, cmd)
		return cmd.Run()
	}
	logger.DebugOp(op, "waiting lock to be acquired...")
	select {
	case lock <- struct{}{}:
		// lock acquired.
		logger.DebugOp(op, "lock acquired")
		if err := resolver(); err != nil {
			<-lock // we release the lock.
			return xerror.New(op, err)
		}
		<-lock // we release the lock.
		return nil
	case <-ctx.Done():
		// failed to acquire lock before
		// deadline.
		logger.DebugOp(op, "failed to acquire lock before context.Context deadline")
		return xerror.New(op, ctx.Err())
	}
}

// Compile-time checks to ensure type implements desired interfaces.
var (
	_ = Printer(new(officePrinter))
)