package d2lib

import (
	"context"
	"errors"
	"os"
	"strings"

	"oss.terrastruct.com/d2/d2compiler"
	"oss.terrastruct.com/d2/d2exporter"
	"oss.terrastruct.com/d2/d2graph"
	"oss.terrastruct.com/d2/d2layouts/d2dagrelayout"
	"oss.terrastruct.com/d2/d2layouts/d2near"
	"oss.terrastruct.com/d2/d2layouts/d2sequence"
	"oss.terrastruct.com/d2/d2renderers/d2fonts"
	"oss.terrastruct.com/d2/d2target"
	"oss.terrastruct.com/d2/lib/textmeasure"
)

type CompileOptions struct {
	UTF16         bool
	MeasuredTexts []*d2target.MText
	Ruler         *textmeasure.Ruler
	Layout        func(context.Context, *d2graph.Graph) error

	// FontFamily controls the font family used for all texts that are not the following:
	// - code
	// - latex
	// - pre-measured (web setting)
	// TODO maybe some will want to configure code font too, but that's much lower priority
	FontFamily *d2fonts.FontFamily
	ThemeID    int64
}

func Compile(ctx context.Context, input string, opts *CompileOptions) (*d2target.Diagram, *d2graph.Graph, error) {
	if opts == nil {
		opts = &CompileOptions{}
	}

	g, err := d2compiler.Compile("", strings.NewReader(input), &d2compiler.CompileOptions{
		UTF16: opts.UTF16,
	})
	if err != nil {
		return nil, nil, err
	}

	if len(g.Objects) > 0 {
		err = g.SetDimensions(opts.MeasuredTexts, opts.Ruler, opts.FontFamily)
		if err != nil {
			return nil, nil, err
		}

		coreLayout, err := getLayout(opts)
		if err != nil {
			return nil, nil, err
		}

		constantNears := d2near.WithoutConstantNears(ctx, g)

		err = d2sequence.Layout(ctx, g, coreLayout)
		if err != nil {
			return nil, nil, err
		}

		err = d2near.Layout(ctx, g, constantNears)
		if err != nil {
			return nil, nil, err
		}
	}

	diagram, err := d2exporter.Export(ctx, g, opts.ThemeID, opts.FontFamily)
	return diagram, g, err
}

func getLayout(opts *CompileOptions) (func(context.Context, *d2graph.Graph) error, error) {
	if opts.Layout != nil {
		return opts.Layout, nil
	} else if os.Getenv("D2_LAYOUT") == "dagre" {
		defaultLayout := func(ctx context.Context, g *d2graph.Graph) error {
			return d2dagrelayout.Layout(ctx, g, nil)
		}
		return defaultLayout, nil
	} else {
		return nil, errors.New("no available layout")
	}
}