framer.go

// Copyright 2017 Pilosa Corp.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// 1. Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
// CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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// NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
// DAMAGE.

package pdk

import (
	"strings"
)

// Framer is an interface for extracting field names from paths denoted by
// []string. The path could be (e.g.) a list of keys in a nested map which
// arrives at a non-container value (string, int, etc).
type Framer interface {
	// The Field method should return an empty string and a nil error if the value
	// at the given path should be ignored. It should return an error, only if
	// something unexpected has occurred which means the record cannot be properly
	// processed.
	Field(path []string) (field string, err error)
}

// FramerFunc is similar to http.HandlerFunc in that you can make a bare
// function satisfy the Framer interface by doing FramerFunc(yourfunc).
type FramerFunc func([]string) (string, error)

// Field on FramerFunc simply calls the wrapped function.
func (f FramerFunc) Field(path []string) (string, error) {
	return f(path)
}

// DashField creates a field name from the path by joining the path elements with
// the "-" character.
type DashField struct {
	Ignore   []string `help:"Do not index paths containing any of these components"`
	Collapse []string `help:"Remove these components from the path before getting field."`
}

func (d *DashField) clean(path []string) []string {
	np := []string{}
OUTER:
	for _, p := range path {
		for _, ig := range d.Ignore {
			if ig == p {
				return nil
			}
		}
		for _, coll := range d.Collapse {
			if coll == p {
				continue OUTER
			}
		}
		np = append(np, strings.TrimSpace(p))
	}
	return np
}

// Field gets a field from a path by joining the path elements with dashes.
func (d *DashField) Field(path []string) (string, error) {
	np := d.clean(path)
	return strings.ToLower(strings.Join(np, "-")), nil
}