predicate.go

/*
Copyright 2014 The Camlistore Authors

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

// These are the search-atom definitions (see expr.go).

package search

import (
	"bytes"
	"encoding/json"
	"fmt"
	"regexp"
	"strconv"
	"strings"
	"time"

	"camlistore.org/pkg/context"
	"camlistore.org/pkg/geocode"
	"camlistore.org/pkg/types"
)

const base = "0000-01-01T00:00:00Z"

var (
	// used for width/height ranges. 10 is max length of 32-bit
	// int (strconv.Atoi on 32-bit platforms), even though a max
	// JPEG dimension is only 16-bit.
	whRangeExpr = regexp.MustCompile(`^(\d{0,10})-(\d{0,10})$`)
	whValueExpr = regexp.MustCompile(`^(\d{1,10})$`)
)

// Atoms holds the parsed words of an atom without the colons.
// Eg. tag:holiday becomes atom{"tag", []string{"holiday"}}
// Note that the form of camlisearch atoms implies that len(args) > 0
type atom struct {
	predicate string
	args      []string
}

func (a atom) String() string {
	s := bytes.NewBufferString(a.predicate)
	for _, a := range a.args {
		s.WriteRune(':')
		s.WriteString(a)
	}
	return s.String()
}

// Keyword determines by its matcher when a predicate is used.
type keyword interface {
	// Name is the part before the first colon, or the whole atom.
	Name() string
	// Description provides user documentation for this keyword.  Should
	// return documentation for max/min values, usage help, or examples.
	Description() string
	// Match gets called with the predicate and arguments that were parsed.
	// It should return true if it wishes to handle this search atom.
	// An error if the number of arguments mismatches.
	Match(a atom) (bool, error)
	// Predicates will be called with the args array from an atom instance.
	// Note that len(args) > 0 (see atom-struct comment above).
	// It should return a pointer to a Constraint object, expressing the meaning of
	// its keyword.
	Predicate(ctx *context.Context, args []string) (*Constraint, error)
}

var keywords []keyword

// RegisterKeyword registers search atom types.
// TODO (sls) Export for applications? (together with keyword and atom)
func registerKeyword(k keyword) {
	keywords = append(keywords, k)
}

// SearchHelp returns JSON of an array of predicate names and descriptions.
func SearchHelp() string {
	type help struct{ Name, Description string }
	h := []help{}
	for _, p := range keywords {
		h = append(h, help{p.Name(), p.Description()})
	}
	b, err := json.MarshalIndent(h, "", "  ")
	if err != nil {
		return "Error marshalling"
	}
	return string(b)
}

func init() {
	// Core predicates
	registerKeyword(newAfter())
	registerKeyword(newBefore())
	registerKeyword(newAttribute())
	registerKeyword(newChildrenOf())
	registerKeyword(newFormat())
	registerKeyword(newTag())
	registerKeyword(newTitle())

	// Image predicates
	registerKeyword(newIsImage())
	registerKeyword(newHeight())
	registerKeyword(newIsLandscape())
	registerKeyword(newIsPano())
	registerKeyword(newIsPortait())
	registerKeyword(newWidth())

	// Custom predicates
	registerKeyword(newIsPost())
	registerKeyword(newIsCheckin())

	// Location predicates
	registerKeyword(newHasLocation())
	registerKeyword(newLocation())
}

// Helper implementation for mixing into keyword implementations
// that match the full keyword, i.e. 'is:pano'
type matchEqual string

func (me matchEqual) Name() string {
	return string(me)
}

func (me matchEqual) Match(a atom) (bool, error) {
	return string(me) == a.String(), nil
}

// Helper implementation for mixing into keyword implementations
// that match only the beginning of the keyword, and get their paramertes from
// the rest, i.e. 'width:' for searches like 'width:100-200'.
type matchPrefix struct {
	prefix string
	count  int
}

func newMatchPrefix(p string) matchPrefix {
	return matchPrefix{prefix: p, count: 1}
}

func (mp matchPrefix) Name() string {
	return mp.prefix
}
func (mp matchPrefix) Match(a atom) (bool, error) {
	if mp.prefix == a.predicate {
		if len(a.args) != mp.count {
			return true, fmt.Errorf("Wrong number of arguments for %q, given %d, expected %d", mp.prefix, len(a.args), mp.count)
		} else {
			return true, nil
		}
	} else {
		return false, nil
	}
}

// Core predicates

type after struct {
	matchPrefix
}

func newAfter() keyword {
	return after{newMatchPrefix("after")}
}

func (a after) Description() string {
	return "date format is RFC3339, but can be shortened as required.\n" +
		"i.e. 2011-01-01 is Jan 1 of year 2011 and \"2011\" means the same."
}

func (a after) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	t, err := parseTimePrefix(args[0])
	if err != nil {
		return nil, err
	}
	tc := &TimeConstraint{}
	tc.After = types.Time3339(t)
	c := &Constraint{
		Permanode: &PermanodeConstraint{
			Time: tc,
		},
	}
	return c, nil
}

type before struct {
	matchPrefix
}

func newBefore() keyword {
	return before{newMatchPrefix("before")}
}

func (b before) Description() string {
	return "date format is RFC3339, but can be shortened as required.\n" +
		"i.e. 2011-01-01 is Jan 1 of year 2011 and \"2011\" means the same."
}

func (b before) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	t, err := parseTimePrefix(args[0])
	if err != nil {
		return nil, err
	}
	tc := &TimeConstraint{}
	tc.Before = types.Time3339(t)
	c := &Constraint{
		Permanode: &PermanodeConstraint{
			Time: tc,
		},
	}
	return c, nil
}

type attribute struct {
	matchPrefix
}

func newAttribute() keyword {
	return attribute{matchPrefix{"attr", 2}}
}

func (a attribute) Description() string {
	return "match on attribute. Use attr:foo:bar to match nodes having their foo\n" +
		"attribute set to bar or attr:foo:~bar to do a substring\n" +
		"case-insensitive search for 'bar' in attribute foo"
}

func (a attribute) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	c := attrConst(args[0], args[1])
	if strings.HasPrefix(args[1], "~") {
		// Substring. Hack. Figure out better way to do this.
		c.Permanode.Value = ""
		c.Permanode.ValueMatches = &StringConstraint{
			Contains:        args[1][1:],
			CaseInsensitive: true,
		}
	}
	return c, nil
}

type childrenOf struct {
	matchPrefix
}

func newChildrenOf() keyword {
	return childrenOf{newMatchPrefix("childrenof")}
}

func (k childrenOf) Description() string {
	return "Find child permanodes of a parent permanode (or prefix of a parent\n" +
		"permanode): childrenof:sha1-527cf12 Only matches permanodes currently."
}

func (k childrenOf) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	c := &Constraint{
		Permanode: &PermanodeConstraint{
			Relation: &RelationConstraint{
				Relation: "parent",
				Any: &Constraint{
					BlobRefPrefix: args[0],
				},
			},
		},
	}
	return c, nil
}

type format struct {
	matchPrefix
}

func newFormat() keyword {
	return format{newMatchPrefix("format")}
}

func (f format) Description() string {
	return "file's format (or MIME-type) such as jpg, pdf, tiff."
}

func (f format) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	mimeType, err := mimeFromFormat(args[0])
	if err != nil {
		return nil, err
	}
	c := permOfFile(&FileConstraint{
		MIMEType: &StringConstraint{
			Equals: mimeType,
		},
	})
	return c, nil
}

type tag struct {
	matchPrefix
}

func newTag() keyword {
	return tag{newMatchPrefix("tag")}
}

func (t tag) Description() string {
	return "match on a tag"
}

func (t tag) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	return attrConst("tag", args[0]), nil
}

type title struct {
	matchPrefix
}

func newTitle() keyword {
	return title{newMatchPrefix("title")}
}

func (t title) Description() string {
	return "match nodes containing substring in their title"
}

func (t title) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	c := &Constraint{
		Permanode: &PermanodeConstraint{
			Attr:       "title",
			SkipHidden: true,
			ValueMatches: &StringConstraint{
				Contains:        args[0],
				CaseInsensitive: true,
			},
		},
	}
	return c, nil
}

// Image predicates

type isImage struct {
	matchEqual
}

func newIsImage() keyword {
	return isImage{"is:image"}
}

func (k isImage) Description() string {
	return "object is an image"
}

func (k isImage) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	c := &Constraint{
		Permanode: &PermanodeConstraint{
			Attr: "camliContent",
			ValueInSet: &Constraint{
				File: &FileConstraint{
					IsImage: true,
				},
			},
		},
	}
	return c, nil
}

type isLandscape struct {
	matchEqual
}

func newIsLandscape() keyword {
	return isLandscape{"is:landscape"}
}

func (k isLandscape) Description() string {
	return "the image has a landscape aspect"
}

func (k isLandscape) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	return whRatio(&FloatConstraint{Min: 1.0}), nil
}

type isPano struct {
	matchEqual
}

func newIsPano() keyword {
	return isPano{"is:pano"}
}

func (k isPano) Description() string {
	return "the image's aspect ratio is over 2 - panorama picture."
}

func (k isPano) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	return whRatio(&FloatConstraint{Min: 2.0}), nil
}

type isPortait struct {
	matchEqual
}

func newIsPortait() keyword {
	return isPortait{"is:portrait"}
}

func (k isPortait) Description() string {
	return "the image has a portrait aspect"
}

func (k isPortait) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	return whRatio(&FloatConstraint{Max: 1.0}), nil
}

type width struct {
	matchPrefix
}

func newWidth() keyword {
	return width{newMatchPrefix("width")}
}

func (w width) Description() string {
	return "use width:min-max to match images having a width of at least min\n" +
		"and at most max. Use width:min- to specify only an underbound and\n" +
		"width:-max to specify only an upperbound.\n" +
		"Exact matches should use width:640 "
}

func (w width) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	mins, maxs, err := parseWHExpression(args[0])
	if err != nil {
		return nil, err
	}
	c := permOfFile(&FileConstraint{
		IsImage: true,
		Width:   whIntConstraint(mins, maxs),
	})
	return c, nil
}

type height struct {
	matchPrefix
}

func newHeight() keyword {
	return height{newMatchPrefix("height")}
}

func (h height) Description() string {
	return "use height:min-max to match images having a height of at least min\n" +
		"and at most max. Use height:min- to specify only an underbound and\n" +
		"height:-max to specify only an upperbound.\n" +
		"Exact matches should use height:480"
}

func (h height) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	mins, maxs, err := parseWHExpression(args[0])
	if err != nil {
		return nil, err
	}
	c := permOfFile(&FileConstraint{
		IsImage: true,
		Height:  whIntConstraint(mins, maxs),
	})
	return c, nil
}

// Location predicates

type location struct {
	matchPrefix
}

func newLocation() keyword {
	return location{newMatchPrefix("loc")}
}

func (l location) Description() string {
	return "matches images and permanodes having a location near\n" +
		"the specified location.  Locations are resolved using\n" +
		"maps.googleapis.com. For example: loc:\"new york, new york\" "
}

func (l location) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	where := args[0]
	rects, err := geocode.Lookup(ctx, where)
	if err != nil {
		return nil, err
	}
	if len(rects) == 0 {
		return nil, fmt.Errorf("No location found for %q", where)
	}
	var c *Constraint
	for i, rect := range rects {
		loc := &LocationConstraint{
			West:  rect.SouthWest.Long,
			East:  rect.NorthEast.Long,
			North: rect.NorthEast.Lat,
			South: rect.SouthWest.Lat,
		}
		fileLoc := permOfFile(&FileConstraint{
			IsImage:  true,
			Location: loc,
		})
		permLoc := &Constraint{
			Permanode: &PermanodeConstraint{
				Location: loc,
			},
		}
		rectConstraint := orConst(fileLoc, permLoc)
		if i == 0 {
			c = rectConstraint
		} else {
			c = orConst(c, rectConstraint)
		}
	}
	return c, nil
}

type hasLocation struct {
	matchEqual
}

func newHasLocation() keyword {
	return hasLocation{"has:location"}
}

func (h hasLocation) Description() string {
	return "matches images and permanodes that have a location (GPSLatitude\n" +
		"and GPSLongitude can be retrieved from the image's EXIF tags)."
}

func (h hasLocation) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	fileLoc := permOfFile(&FileConstraint{
		IsImage: true,
		Location: &LocationConstraint{
			Any: true,
		},
	})
	permLoc := &Constraint{
		Permanode: &PermanodeConstraint{
			Location: &LocationConstraint{
				Any: true,
			},
		},
	}
	return orConst(fileLoc, permLoc), nil
}

// Helpers

func attrConst(attr, val string) *Constraint {
	c := &Constraint{
		Permanode: &PermanodeConstraint{
			Attr:       attr,
			SkipHidden: true,
		},
	}
	if val == "" {
		c.Permanode.ValueMatches = &StringConstraint{Empty: true}
	} else {
		c.Permanode.Value = val
	}
	return c
}

func permOfFile(fc *FileConstraint) *Constraint {
	return &Constraint{
		Permanode: &PermanodeConstraint{
			Attr:       "camliContent",
			ValueInSet: &Constraint{File: fc},
		},
	}
}

func whRatio(fc *FloatConstraint) *Constraint {
	return permOfFile(&FileConstraint{
		IsImage: true,
		WHRatio: fc,
	})
}

func parseWHExpression(expr string) (min, max string, err error) {
	if m := whRangeExpr.FindStringSubmatch(expr); m != nil {
		return m[1], m[2], nil
	}
	if m := whValueExpr.FindStringSubmatch(expr); m != nil {
		return m[1], m[1], nil
	}
	return "", "", fmt.Errorf("Unable to parse %q as range, wanted something like 480-1024, 480-, -1024 or 1024", expr)
}

func parseTimePrefix(when string) (time.Time, error) {
	if len(when) < len(base) {
		when += base[len(when):]
	}
	return time.Parse(time.RFC3339, when)
}

func whIntConstraint(mins, maxs string) *IntConstraint {
	ic := &IntConstraint{}
	if mins != "" {
		if mins == "0" {
			ic.ZeroMin = true
		} else {
			n, _ := strconv.Atoi(mins)
			ic.Min = int64(n)
		}
	}
	if maxs != "" {
		if maxs == "0" {
			ic.ZeroMax = true
		} else {
			n, _ := strconv.Atoi(maxs)
			ic.Max = int64(n)
		}
	}
	return ic
}

func mimeFromFormat(v string) (string, error) {
	if strings.Contains(v, "/") {
		return v, nil
	}
	switch v {
	case "jpg", "jpeg":
		return "image/jpeg", nil
	case "gif":
		return "image/gif", nil
	case "png":
		return "image/png", nil
	case "pdf":
		return "application/pdf", nil // RFC 3778
	}
	return "", fmt.Errorf("Unknown format: %s", v)
}

// Custom predicates

type isPost struct {
	matchEqual
}

func newIsPost() keyword {
	return isPost{"is:post"}
}

func (k isPost) Description() string {
	return "matches tweets, status updates, blog posts, etc"
}

func (k isPost) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	return &Constraint{
		Permanode: &PermanodeConstraint{
			Attr:  "camliNodeType",
			Value: "twitter.com:tweet",
		},
	}, nil
}

type isCheckin struct {
	matchEqual
}

func newIsCheckin() keyword {
	return isCheckin{"is:checkin"}
}

func (k isCheckin) Description() string {
	return "matches location check-ins (foursquare, etc)"
}

func (k isCheckin) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
	return &Constraint{
		Permanode: &PermanodeConstraint{
			Attr:  "camliNodeType",
			Value: "foursquare.com:checkin",
		},
	}, nil
}