--------------------------------------------------------------------------------
--  Copyright (c) 2011-2012 Sierra Wireless.
--  All rights reserved. This program and the accompanying materials
--  are made available under the terms of the Eclipse Public License v1.0
--  which accompanies this distribution, and is available at
--  http://www.eclipse.org/legal/epl-v10.html
--
--  Contributors:
--       Kevin KIN-FOO <kkinfoo@sierrawireless.com>
--           - initial API and implementation and initial documentation
--------------------------------------------------------------------------------
---
-- This library provide html description of elements from the externalapi
local M = {}

-- Load template engine
local pltemplate = require 'pl.template'

-- Markdown handling
local markdown = require 'markdown'

-- apply template to the given element
function M.applytemplate(elem, ident, templatetype,...)
  -- define environment
  local env = M.getenv(elem, ident,...)

  -- load template
  local template = M.gettemplate(elem,templatetype)
  if not template then
    templatetype = templatetype and string.format(' "%s"', templatetype) or ''
    local elementname = string.format(' for %s', elem.tag or 'untagged element')
    error(string.format('Unable to load %s template %s', templatetype, elementname))
  end

  -- apply template
  local str, err = pltemplate.substitute(template, env)

  --manage errors
  if not str then
    local templateerror = templatetype and string.format(' parsing "%s" template ', templatetype) or ''
    error(string.format('An error occured%s for "%s"\n%s',templateerror, elem.tag, err))
  end
  return str
end

-- get the a new environment for this element
function M.getenv(elem, ident,...)
  local currentenv ={}
  for k,v in pairs(M.env) do currentenv[k] = v end
  if elem and elem.tag then
    currentenv['_'..elem.tag]= elem
  end
  currentenv['i']= ident or 1
  currentenv['templateparams']= {...}
  return currentenv
end

-- get the template for this element
function M.gettemplate(elem,templatetype)
  local tag = elem and elem.tag
  if tag then
    if templatetype then
      return require ("template." .. templatetype.. "." .. tag)
    else
      return require ("template." .. tag)
    end
  end
end


---
-- Allow user to format text in descriptions.
-- Default implementation replaces @{---} tags with links and apply markdown.
-- @return #string
local function format(string)
  -- Allow to replace encountered tags with valid links
  local replace = function(found)
    local apiobj = M.env.getelement(found)
    if apiobj then
      return M.env.fulllinkto(apiobj)
    end
    return found
  end
  string = string:gsub('@{%s*(.-)%s*}', replace)
  return M.env.markdown( string )
end

---
-- Provide a full link to an element using `prettyname` and `linkto`.
-- Default implementation is for HTML.
local function fulllinkto(o,...)
  local ref   = M.env.linkto(o,...)
  local name  = M.env.prettyname(o,...)
  if not ref then
    return name
  end
  return string.format('<a href="%s">%s</a>', ref, name)
end
--
-- Define default template environnement
--
local defaultenv = {
  table         = table,
  ipairs        = ipairs,
  pairs         = pairs,
  markdown      = markdown,
  applytemplate = M.applytemplate,
  format        = format,
  linkto        = function(str) return str end,
  fulllinkto    = fulllinkto,
  prettyname    = function(s) return s end,
  getelement    = function(s) return nil end
}

-- this is the global env accessible in the templates
-- env should be redefine by docgenerator user to add functions or redefine it.
M.env = defaultenv
return M