Class: Intranet::Pictures::JsonDbProvider

Inherits:
Object
  • Object
show all
Defined in:
lib/intranet/pictures/json_db_provider.rb

Overview

Provides pictures data and pictures listings from a database file in JSON format.

Structure of the JSON database

See the example below.

Pictures are described individually as a hash in the pictures array. The mandatory keys in this hash are:

  • uri : location of the picture, relative to the JSON file (string)
  • title : description of the picture (string)
  • datetime : date and time of the picture, in ISO8601 format (string)
  • height and width : size in pixels of the picture (integers)

Additional keys may be added (for instance: event, city, region/country, ...); they will be used to select pictures sharing the same value of a given key, or to group them. Values may either be singular string elements (for instance: "My wonderful event") or array of strings (for instance: [ "Casino", "Las Vegas", "Urban photography" ]).

Some groups may be defined in the groups hash to add a thumbnail picture and a brief text description for them. The possible keys in this hash are:

  • id : unique identifier of the group, mandatory (string)
  • brief : optional short text associated to the group name (string)
  • uri : optional group thumbnail, relative to the JSON file (string)

Examples:

Structure of the JSON database (not all mandatory keys are present for readability)

{
  "groups": {
    "event": [
      { "id": "Party", "brief": "...", "uri": "party.jpg", ... },
      { ... }
    ],
    "city": [
      { "id": "Houston", "uri": "houston.png", ... },
      { ... }
    ]
  },
  "pictures": [
    { "uri": "dir/pic0.jpg", "datetime": "...", "event": "Party", "city": "Houston",
      "tags": [ "USA", "Portrait" ], ... },
    { ... }
  ]
}

Instance Method Summary collapse

Constructor Details

#initialize(json_file) ⇒ JsonDbProvider

Initializes a new pictures data provider.

Parameters:

  • json_file (String) —

    The path to the JSON database file.



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# File 'lib/intranet/pictures/json_db_provider.rb', line 52

def initialize(json_file)
  @json_dir = File.dirname(json_file) # also works for URLs
  @json_file = json_file
  @json_time = Time.at(0)
  load_json
end

Instance Method Details

#group_brief(key, value) ⇒ String

Returns the brief text of the group whose type is key and named value.

Parameters:

  • key (String) —

    The group type.

  • value (String) —

    The group name.

Returns:

  • (String) —

    The brief text of the group, or an empty string if no brief is available.

Raises:

  • KeyError If JSON file is malformed or if key/value do not designate exactly one group.



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# File 'lib/intranet/pictures/json_db_provider.rb', line 129

def group_brief(key, value)
  load_json
  group = select_group(key, value)
  raise KeyError unless group.size == 1
  return '' if group.first['brief'].nil?

  group.first.fetch('brief')
end

#group_thumbnail(key, value) ⇒ String, Blob

Returns the thumbnail picture of the group whose type is key and named value.

Parameters:

  • key (String) —

    The group type.

  • value (String) —

    The group name.

Returns:

  • (String, Blob) —

    The MIME type of the picture, and the picture file content. Nil may be returned if no thumbnail is available for that group.

Raises:

  • KeyError If JSON file is malformed, if key/value do not designate exactly one group, or if the group uri does not refer to an existing image file.



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# File 'lib/intranet/pictures/json_db_provider.rb', line 113

def group_thumbnail(key, value)
  load_json
  group = select_group(key, value)
  raise KeyError unless group.size == 1
  return nil if group.first['uri'].nil?

  path = File.join(@json_dir, group.first.fetch('uri'))
  read_image_file(path)
end

#list_pictures(selector = {}, sort_by = nil, asc = true) ⇒ Array<Hash{'title'=>String, 'datetime'=>String, 'height'=>Integer, 'width'=>Integer, ...}>

Returns the list of the pictures matching the given selectors. Selectors are key/value strings pairs restricting the pictures to be returned:

- if a picture has the given key, its value is a singular string and is strictly equal
to the given value, it is returned;
- if a picture has the given key, its value is an array of strings and ONE of the
elements of this array is equal to the given value, it is returned;
- all other pictures are not returned.

Results are sorted according to the value of the key sort_by, in ascending order if asc, and in descending order otherwise. Sorting by a key whose value is not a singular string is not defined.

Parameters:

  • selector (Hash<String,String>) (defaults to: {}) —

    The pictures selector, interpreted as a logical AND combination of all key/value pairs provided.

  • sort_by (String) (defaults to: nil) —

    The picture field to sort the results by, or nil if results should be returned without particular sorting.

  • asc (Boolean) (defaults to: true) —

    True to sort returned pictures in ascending order, False to sort them in descending order.

Returns:

  • (Array<Hash{'title'=>String, 'datetime'=>String, 'height'=>Integer, 'width'=>Integer, ...}>) —

    The selected pictures.

Raises:

  • KeyError If JSON file is malformed, or if sort_by is not an existing picture field, or if sort_by is not a singular string value.



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# File 'lib/intranet/pictures/json_db_provider.rb', line 79

def list_pictures(selector = {}, sort_by = nil, asc = true)
  load_json
  pics = select_pictures(selector).map { |p| p.except('uri') }
  unless sort_by.nil?
    raise KeyError if pics.any? { |p| p.fetch(sort_by).respond_to?('any?') }

    pics.sort_by! { |p| p.fetch(sort_by) }
  end
  pics.reverse! unless asc
  pics
end

#picture(selector = {}) ⇒ String, Blob

Returns the picture file matching selector.

Parameters:

  • selector (Hash<String,String>) (defaults to: {}) —

    The picture selector, which should return exactly one picture.

Returns:

  • (String, Blob) —

    The MIME type of the picture, and the picture file content.

Raises:

  • KeyError If JSON file is malformed, if selector does not match exactly one picture, or if the picture uri does not refer to an existing image file.



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# File 'lib/intranet/pictures/json_db_provider.rb', line 97

def picture(selector = {})
  load_json
  pic = select_pictures(selector)
  raise KeyError unless pic.size == 1

  path = File.join(@json_dir, pic.first.fetch('uri'))
  read_image_file(path)
end