package main

import (
	"fmt"
	"os"

	"github.com/davecgh/go-spew/spew"
	"github.com/hashicorp/hcl/v2"
	"github.com/hashicorp/hcl/v2/hcldec"
	"github.com/hashicorp/hcl/v2/hclparse"
	"github.com/zclconf/go-cty/cty"
	"github.com/zclconf/go-cty/cty/gocty"
)

func main() {
	err := realMain()
	if err != nil {
		fmt.Fprintf(os.Stderr, "ERROR: %s\n", err)
		os.Exit(1)
	}
}

type MapDetails struct {
	Width    int `cty:"width"`
	FontSize int `cty:"font_size"`
}

type NestedMapDetails struct {
	Size *Size `cty:"size"`
}

type Size struct {
	Width    int `cty:"width"`
	FontSize int `cty:"font_size"`
}

// type NestedMapDetails struct {
// 	Size struct {
// 		Width    int `cty:"width"`
// 		FontSize int `cty:"font_size"`
// 	} `cty:"size"`
// }

func realMain() error {
	var mapDetailsSpec = &hcldec.ObjectSpec{
		"width": &hcldec.AttrSpec{
			Name:     "width",
			Required: false,
			Type:     cty.Number,
		},
		"font_size": &hcldec.AttrSpec{
			Name:     "font_size",
			Required: false,
			Type:     cty.Number,
		},
	}

	var data = `
width = 100
font_size = 9
	`

	val, err := do([]byte(data), "test.hcl", mapDetailsSpec)
	if err != nil {
		return err
	}
	var mapDetails MapDetails
	err = gocty.FromCtyValue(val, &mapDetails)
	if err != nil {
		return err
	}
	spew.Dump(mapDetails)

	var nestedMapDetailsSpec = &hcldec.ObjectSpec{
		"size": &hcldec.BlockListSpec{
			TypeName: "size",
			Nested: &hcldec.ObjectSpec{
				"width": &hcldec.AttrSpec{
					Name:     "width",
					Required: false,
					Type:     cty.Number,
				},
				"font_size": &hcldec.AttrSpec{
					Name:     "font_size",
					Required: false,
					Type:     cty.Number,
				},
			},
		},
	}

	data = `size {
	width = 100
	font_size = 9
}
	`
	val, err = do([]byte(data), "test.hcl", nestedMapDetailsSpec)
	if err != nil {
		return err
	}
	var nestedMapDetails NestedMapDetails
	err = gocty.FromCtyValue(val, &nestedMapDetails)
	if err != nil {
		return err
	}
	spew.Dump(nestedMapDetails)
	return nil
}

func do(data []byte, filename string, spec *hcldec.ObjectSpec) (cty.Value, error) {
	parser := hclparse.NewParser()
	f, diags := parser.ParseHCL([]byte(data), filename)
	val, moreDiags := hcldec.Decode(f.Body, spec, nil)
	diags = append(diags, moreDiags...)
	if diags.HasErrors() {
		wr := hcl.NewDiagnosticTextWriter(
			os.Stderr,      // writer to send messages to
			parser.Files(), // the parser's file cache, for source snippets
			100,            // wrapping width
			true,           // generate colored/highlighted output
		)
		wr.WriteDiagnostics(diags)
		return val, fmt.Errorf("failure during decoding")
	}
	return val, nil
}