Webscript: Guidelines

Identifies the webscript to the library.

Must set the following fields.

• self.domain (pattern, e.g.  “video.google.”)
• self.formats (‘default’ or ‘default|best’ if >1 formats)
• self.categories (protocol category of script)
• self.handles (whether script can handle the URL)

Queries the available formats to an URL.

Must set the following fields.

• self.formats (‘default’ or a dynamically created if >1 formats)

See youtube.lua, cbsnews.lua, dailymotion.lua and vimeo.lua for examples of >1 formats.

Parsing errors should raise an error.

Parses the media details.

Must set the following fields.

• self.host_id
• self.title
• self.id
• self.url (NOTE: an array of URLs)

Set these if data is available or otherwise applicable.

• self.thumbnail_url (see youtube.lua)
• self.redirect_url (academicearth.lua)
• self.start_time (youtube.lua)
• self.duration (soundcloud.lua)

Important notes.

• Fallback to ‘default’ if self.requested_format value is not recognized

Parsing (e.g. no match) should call lua’s error function.  Note however that format parsing is exception to this rule:

• Script must fallback to ‘default’ format and only if that fails too, exit with an error

Useful tips.

quvi.fetch

• Use sparingly
• Set fetch_type only if fetching other than ‘page’ (default)
• Set arbitrary_cookie only when absolutely necessary (dailymotion.lua)
• Set user_agent only when absolutely necessary (globo.lua)

quvi.resolve

• Use sparingly (see blip.lua)

Additional modules with functions.  These can be imported in your script.  Use them sparingly.

local U = require 'quvi/util'
local bar = U.unescape(foo)

See the quvi/ subdir in the website/ directory for the other modules.

Useful lua idioms.

/* Consider the following in C */
b = (a == 1) 0:1;

-- Equivalent in lua:
b = (a == 1) and 0 or 1

Armed with this knowledge, consider the following.

local foo
if bar == 'baz' then
    foo = 'foo'
else
    foo = 'bar'
end

Could also be written like this.

local foo = (bar == 'baz') and 'foo' or 'bar'

Related pages.

• Overview: Formats