package step

import "io"
import "time"
import "strings"
import "html/template"

// Document represents a STEP file.
type Document struct {
	Author  string
	Title   string
	Extends string
	
	// WORM:
	environment *Environment
	frontMatter FrontMatter
	name        string
	parseTime   time.Time
	template    *template.Template
}

// Execute executes this document and writes the result to the output. This
// method is safe for concurrent use by multiple goroutines.
func (this *Document) Execute (output io.Writer, data ExecutionData) error {
	if this.Extends == "" {
		// no parent
		return this.template.Execute(output, data)
	}

	// execute into string builder
	outputBuilder := strings.Builder { }
	err := this.template.Execute(&outputBuilder, data)
	if err != nil { return err }

	// execute parent with this document's result
	parent, err := this.environment.Parse(this.Extends)
	if err != nil { return err }
	return parent.Execute(output, ExecutionData {
		Data:  data.Data,
		Child: &ExecutionResult {
			Author:      this.Author,
			Title:       this.Title,
			Extends:     this.Extends,
			FrontMatter: this.frontMatter,
			Body:        template.HTML(outputBuilder.String()),
		},
	})
}

// ExecutionData is data made available to documents as they are being exeucted.
type ExecutionData struct {
	Data any               // Custom data
	Child *ExecutionResult // The child document's result, if applicable
}

// ExecutionResult is the result of executing a document.
type ExecutionResult struct {
	Author  string
	Title   string
	Extends string
	
	FrontMatter FrontMatter
	Body template.HTML
}