package template_nest


import (
    "encoding/json"
    "log"
    "regexp"
)


type Nest struct {

    templateLabel string
    templateDir string
    templates map[string]string
    tokenDelims [2]string

}


func New( templates map[string]string ) Nest {

    nest := Nest{
        templateLabel: "TEMPLATE",
        tokenDelims: [2]string{"<!--%", "%-->"},
        templates: templates,
    }

    return nest
}




func (obj *Nest) Render ( sjson []byte ) string {

    var nesti interface{}
    err := json.Unmarshal(sjson, &nesti)
    if err != nil {
      log.Fatal("Failed to parse JSON")
    }

    nested := nesti.(map[string]interface{})

    html := obj._Render( nested )

    return html

}


func (obj *Nest) _Render( nested interface{} ) string{

    var html string

    switch vtype := nested.(type) {

        case string:
            html = vtype

        case []interface{}:

            html = obj._RenderArray( vtype )

        case map[string]interface{}:
            html = obj._RenderMap( vtype )

    }

    return html

}


func (obj *Nest) _RenderArray( nested []interface{} ) string {

    html := ""
    for v := range nested {
        html += obj._Render( v )
    }

    return html
}




func (obj *Nest) _RenderMap( nested map[string]interface{} ) string {

    templateName := nested[ obj.templateLabel ].(string)
    if templateName == "" {
        panic("Encountered map with no TEMPLATE label")
    }

    template := obj.templates[ templateName ]

    params := make(map[string]string)

    for k, v := range nested {

        if k == obj.templateLabel {
            continue
        }

        params[ k ] = obj._Render( v )

    }

    html := obj._FillIn( templateName, template, params )

    return html

}


func (obj *Nest) _FillIn( templateName string, template string, params map[string]string ) string {

    html := template
    for param, val := range params {

        regex, err := regexp.Compile( obj.tokenDelims[0] + `\s*` + param + `\s*` + obj.tokenDelims[1] )
        if err != nil {
            panic( err )
        }

        html = regex.ReplaceAllString( html, val )

    }

    return html
}