gists/pt.lua

require('extra')

local pt = {}
pt.__index = pt
setmetatable(pt, pt)

function rawstr(v)
    if v == nil then return 'nil' end
    local mt = getmetatable(v)
    local ts = mt and rawget(mt, '__tostring')
    if not ts then return tostring(v) end
    mt.__tostring = nil
    local s = tostring(v)
    mt.__tostring = ts
    return s
end

function getaddr(t)
    return rawstr(t):sub(#type(t) + 3)
end

function pt.__call(pt, t, writer, seen)
    -- print a table as semi-valid YAML
    -- with references to prevent recursion/duplication
    local self = {}
    setmetatable(self, pt)
    self.seen = seen or {}
    self.queued = {}
    self.writer = writer or io.write
    self:inner('__root__', t, '')
    return self.seen
end

function pt:write(...)
    self.writer(...)
end

function pt.safekey(k)
    if type(k) == 'table' then
        return 't'..getaddr(k)
    end
    local s = tostring(k)
    s = s:gsub('[\r\n]', '')
    return s:find('[^%w_]') and ('%q'):format(s) or s
end

function pt.safeval(v, indent)
    if type(v) == 'function' then
        return 'f'..getaddr(v)
    end
    local s = tostring(v)
    if type(v) == 'number' then
        return s
    end
    s = s:find('[\r\n]') and ('\n'..s):gsub('[\r\n]', '\n'..indent..' ') or s
    local safe = ('%q'):format(s)
    return s == safe:sub(2, -2) and s or safe
end

function pt:inner(k, v, indent)
    if type(v) ~= 'table' then
        self:write(indent, pt.safekey(k), ': ')
        self:write(pt.safeval(v, indent), '\n')
        return
    end

    local addr = getaddr(v)

    self:write(indent, pt.safekey(k))
    if self.seen[addr] or self.queued[addr] then
        self:write(': *t', addr, '\n')
        return
    end

    self.seen[addr] = true

    self:write(': &t', addr, '\n')
    self:outer(v, indent..' ')
end

function pt:outer(t, indent)
    if type(t) ~= "table" then
        self:write(indent, pt.safeval(t, indent), '\n')
        return
    end

    local ours = {}
    local not_ours = {}

    for k,v in opairs(t) do
        if type(v) == 'table' then
            local addr = getaddr(v)
            if not self.queued[addr] and not self.seen[addr] then
                self.queued[addr] = true
                ours[k] = v
            else
                not_ours[k] = v
            end
        else
            self:inner(k, v, indent)
        end
    end

    for k,v in opairs(not_ours) do
        self:inner(k, v, indent)
    end

    for k,v in opairs(ours) do
        self.queued[getaddr(v)] = nil
        self:inner(k, v, indent)
    end

    local mt = getmetatable(t)
    if mt ~= nil then
        self:inner('__metatable', mt, indent)
    end
end

return pt