package hcl2template

import (
	"fmt"

	"github.com/hashicorp/hcl/v2"
)

// A source field in an HCL file will load into the Source type.
//
type Source struct {
	// Type of source; ex: virtualbox-iso
	Type string
	// Given name; if any
	Name string

	Cfg interface{}

	HCL2Ref HCL2Ref
}

func (p *Parser) decodeSource(block *hcl.Block, sourceSpecs map[string]Decodable) (*Source, hcl.Diagnostics) {
	source := &Source{
		Type: block.Labels[0],
		Name: block.Labels[1],
	}
	source.HCL2Ref.DeclRange = block.DefRange

	var diags hcl.Diagnostics

	sourceSpec, found := sourceSpecs[source.Type]
	if !found {
		diags = append(diags, &hcl.Diagnostic{
			Summary: "Unknown " + sourceLabel + " type",
			Subject: &block.LabelRanges[0],
		})
		return source, diags
	}

	flatSource, moreDiags := decodeDecodable(block, nil, sourceSpec)
	diags = append(diags, moreDiags...)
	source.Cfg = flatSource

	return source, diags
}

func (source *Source) Ref() SourceRef {
	return SourceRef{
		Type: source.Type,
		Name: source.Name,
	}
}

type SourceRef struct {
	Type string
	Name string
}

// NoSource is the zero value of sourceRef, representing the absense of an
// source.
var NoSource SourceRef

func sourceRefFromAbsTraversal(t hcl.Traversal) (SourceRef, hcl.Diagnostics) {
	var diags hcl.Diagnostics
	if len(t) != 3 {
		diags = append(diags, &hcl.Diagnostic{
			Severity: hcl.DiagError,
			Summary:  "Invalid " + sourceLabel + " reference",
			Detail:   "A " + sourceLabel + " reference must have three parts separated by periods: the keyword \"" + sourceLabel + "\", the builder type name, and the source name.",
			Subject:  t.SourceRange().Ptr(),
		})
		return NoSource, diags
	}

	if t.RootName() != sourceLabel {
		diags = append(diags, &hcl.Diagnostic{
			Severity: hcl.DiagError,
			Summary:  "Invalid " + sourceLabel + " reference",
			Detail:   "The first part of an source reference must be the keyword \"" + sourceLabel + "\".",
			Subject:  t[0].SourceRange().Ptr(),
		})
		return NoSource, diags
	}
	btStep, ok := t[1].(hcl.TraverseAttr)
	if !ok {
		diags = append(diags, &hcl.Diagnostic{
			Severity: hcl.DiagError,
			Summary:  "Invalid " + sourceLabel + " reference",
			Detail:   "The second part of an " + sourceLabel + " reference must be an identifier giving the builder type of the " + sourceLabel + ".",
			Subject:  t[1].SourceRange().Ptr(),
		})
		return NoSource, diags
	}
	nameStep, ok := t[2].(hcl.TraverseAttr)
	if !ok {
		diags = append(diags, &hcl.Diagnostic{
			Severity: hcl.DiagError,
			Summary:  "Invalid " + sourceLabel + " reference",
			Detail:   "The third part of an " + sourceLabel + " reference must be an identifier giving the name of the " + sourceLabel + ".",
			Subject:  t[2].SourceRange().Ptr(),
		})
		return NoSource, diags
	}

	return SourceRef{
		Type: btStep.Name,
		Name: nameStep.Name,
	}, diags
}

func (r SourceRef) String() string {
	return fmt.Sprintf("%s.%s", r.Type, r.Name)
}