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88 lines
3.1 KiB
88 lines
3.1 KiB
-- Simple template language
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--
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-- The new() function takes a pattern and an escape function and returns
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-- a render() function. Both are required.
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--
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-- The function render() takes a string template and a table of values.
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-- Sequences like {name} in the template string are substituted
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-- with values from the table, optionally depending on a modifier
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-- symbol.
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--
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-- Variants are:
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-- {name} is substituted for values["name"] and is escaped using the
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-- second argument to new_render(). To disable the escaping, use {name!}.
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-- {name.item} can be used to access table items.
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-- To renter lists of items: {name# item number {idx} is {item} }
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-- Or key-value pairs: {name% t[ {idx} ] = {item} }
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-- To show a defaults for missing values {name? sub-template } can be used,
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-- which renders a sub-template if values["name"] is false-ish.
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-- {name& sub-template } does the opposite, the sub-template is rendered
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-- if the selected value is anything but false or nil.
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local type, tostring = type, tostring;
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local pairs, ipairs = pairs, ipairs;
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local s_sub, s_gsub, s_match = string.sub, string.gsub, string.match;
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local t_concat = table.concat;
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local function new_render(pat, escape, funcs)
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-- assert(type(pat) == "string", "bad argument #1 to 'new_render' (string expected)");
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-- assert(type(escape) == "function", "bad argument #2 to 'new_render' (function expected)");
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local function render(template, values)
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-- assert(type(template) == "string", "bad argument #1 to 'render' (string expected)");
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-- assert(type(values) == "table", "bad argument #2 to 'render' (table expected)");
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return (s_gsub(template, pat, function (block)
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block = s_sub(block, 2, -2);
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local name, raw, opt, e = s_match(block, "^([%a_][%w_.]*)(!?)(%p?)()");
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if not name then return end
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local value = values[name];
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if not value and name:find(".", 2, true) then
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value = values;
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for word in name:gmatch"[^.]+" do
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value = value[word];
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if not value then break; end
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end
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end
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if funcs then
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while opt == '|' do
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local f;
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f, raw, opt, e = s_match(block, "^([%a_][%w_.]*)(!?)(%p?)()", e);
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f = funcs[f];
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if value ~= nil and f then value = f(value); end
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end
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end
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if opt == '#' or opt == '%' then
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if type(value) ~= "table" then return ""; end
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local iter = opt == '#' and ipairs or pairs;
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local out, i, subtpl = {}, 1, s_sub(block, e);
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local subvalues = setmetatable({}, { __index = values });
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for idx, item in iter(value) do
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subvalues.idx = idx;
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subvalues.item = item;
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out[i], i = render(subtpl, subvalues), i+1;
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end
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return t_concat(out);
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elseif opt == '&' then
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if not value then return ""; end
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return render(s_sub(block, e), values);
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elseif opt == '~' then
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if value then return ""; end
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return render(s_sub(block, e), values);
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elseif opt == '?' and not value then
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return render(s_sub(block, e), values);
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elseif value ~= nil then
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if type(value) ~= "string" then
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value = tostring(value);
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end
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if raw ~= '!' then
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return escape(value);
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end
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return value;
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end
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end));
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end
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return render;
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end
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return {
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new = new_render;
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};
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