package webutility
  
  import (
  	"fmt"
  	"net/http"

  	"net/url"

  	"strings"
  )

  type Filter map[string][]string

  func (f Filter) Get(key string) (values []string, ok bool) {
  	values, ok = f[key]
  	return values, ok

  }

  func (f Filter) Size() int {
  	return len(f)
  }
  
  func (f Filter) IsNotEmpty() bool {
  	return len(f) > 0

  }

  func (fs Filter) validate(validFilters []string) (Filter, bool) {

  	goodFilters := make(Filter)
  	cnt, len := 0, 0

  	for f, _ := range fs {
  		len++
  		for _, v := range validFilters {
  			if f == v {
  				cnt++
  				goodFilters[f] = fs[f]
  			}
  		}
  	}
  
  	result := true
  	if len > 0 && cnt == 0 {
  		// if no valid filters are found declare filtering request as invalid
  		result = false
  	}
  
  	return goodFilters, result
  }
  
  // requires input in format: "param1::value1|param2::value2..."
  func ParseFilters(req *http.Request, header string) (filters Filter) {
  	q := req.FormValue(header)
  	q = strings.Trim(q, "\"")
  	kvp := strings.Split(q, "|")

  	filters = make(Filter, len(kvp))

  
  	for i, _ := range kvp {
  		kv := strings.Split(kvp[i], "::")
  		if len(kv) == 2 {

  			key, _ := url.QueryUnescape(kv[0])

  
  			// get values (if more than 1)
  			vals := strings.Split(kv[1], ",")
  			for _, v := range vals {
  				u, _ := url.QueryUnescape(v)
  				filters[key] = append(filters[key], u)
  			}

  		}
  	}
  
  	return filters
  }

  // TODO(marko): very dodgy, needs more robustness

  func MakeFilterString(prefix string, filters Filter, validFilters []string) (res string, ok bool) {
  	if prefix != "" {
  		prefix += "."
  	}

  
  	if !filters.IsNotEmpty() {

  		return "", true
  	}
  
  	filters, ok = filters.validate(validFilters)
  	if !ok {

  		return "", false

  	}

  	for k, filter := range filters {
  		first := true
  		symbol := "="
  
  		if first {

  			res += " and "

  			first = false

  		} else {
  			res += " where "
  		}

  		res += "("
  		for i, f := range filter {
  			if strings.HasPrefix(f, "<") || strings.HasPrefix(f, ">") {
  				symbol = string(f[0])
  				f = strings.TrimLeft(f, "<>")
  				if strings.HasPrefix(f, "=") {
  					f = strings.TrimLeft(f, "=")
  					symbol += "="
  				}
  			}
  
  			res += fmt.Sprintf("%s%s %s '%s'", prefix, k, symbol, f)
  
  			if i < len(filter)-1 {
  				res += " or "
  			}
  		}
  		res += ")"

  	}
  
  	return res, ok
  }