local inspect = {
    _VERSION = 'inspect.lua 3.1.0',
    _URL = 'http://github.com/kikito/inspect.lua',
    _DESCRIPTION = 'human-readable representations of tables',
    _LICENSE = [[
    MIT LICENSE

    Copyright (c) 2013 Enrique García Cota

    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the
    "Software"), to deal in the Software without restriction, including
    without limitation the rights to use, copy, modify, merge, publish,
    distribute, sublicense, and/or sell copies of the Software, and to
    permit persons to whom the Software is furnished to do so, subject to
    the following conditions:

    The above copyright notice and this permission notice shall be included
    in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
    OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
    IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
    CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
    TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
    SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  ]]
}

local tostring = tostring

inspect.KEY =
    setmetatable(
    {},
    {
        __tostring = function()
            return 'inspect.KEY'
        end
    }
)
inspect.METATABLE =
    setmetatable(
    {},
    {
        __tostring = function()
            return 'inspect.METATABLE'
        end
    }
)

-- Apostrophizes the string if it has quotes, but not aphostrophes
-- Otherwise, it returns a regular quoted string
local function smartQuote(str)
    if str:match('"') and not str:match("'") then
        return "'" .. str .. "'"
    end
    return '"' .. str:gsub('"', '\\"') .. '"'
end

-- \a => '\\a', \0 => '\\0', 31 => '\31'
local shortControlCharEscapes = {
    ['\a'] = '\\a',
    ['\b'] = '\\b',
    ['\f'] = '\\f',
    ['\n'] = '\\n',
    ['\r'] = '\\r',
    ['\t'] = '\\t',
    ['\v'] = '\\v'
}
local longControlCharEscapes = {} -- \a => nil, \0 => \000, 31 => \031
for i = 0, 31 do
    local ch = string.char(i)
    if not shortControlCharEscapes[ch] then
        shortControlCharEscapes[ch] = '\\' .. i
        longControlCharEscapes[ch] = string.format('\\%03d', i)
    end
end

local function escape(str)
    return (str:gsub('\\', '\\\\'):gsub('(%c)%f[0-9]', longControlCharEscapes):gsub('%c', shortControlCharEscapes))
end

local function isIdentifier(str)
    return type(str) == 'string' and str:match('^[_%a][_%a%d]*$')
end

local function isSequenceKey(k, sequenceLength)
    return type(k) == 'number' and 1 <= k and k <= sequenceLength and math.floor(k) == k
end

local defaultTypeOrders = {
    ['number'] = 1,
    ['boolean'] = 2,
    ['string'] = 3,
    ['table'] = 4,
    ['function'] = 5,
    ['userdata'] = 6,
    ['thread'] = 7
}

local function sortKeys(a, b)
    local ta, tb = type(a), type(b)

    -- strings and numbers are sorted numerically/alphabetically
    if ta == tb and (ta == 'string' or ta == 'number') then
        return a < b
    end

    local dta, dtb = defaultTypeOrders[ta], defaultTypeOrders[tb]
    -- Two default types are compared according to the defaultTypeOrders table
    if dta and dtb then
        return defaultTypeOrders[ta] < defaultTypeOrders[tb]
    elseif dta then
        return true -- default types before custom ones
    elseif dtb then
        return false -- custom types after default ones
    end

    -- custom types are sorted out alphabetically
    return ta < tb
end

-- For implementation reasons, the behavior of rawlen & # is "undefined" when
-- tables aren't pure sequences. So we implement our own # operator.
local function getSequenceLength(t)
    local len = 1
    local v = rawget(t, len)
    while v ~= nil do
        len = len + 1
        v = rawget(t, len)
    end
    return len - 1
end

local function getNonSequentialKeys(t)
    local keys = {}
    local sequenceLength = getSequenceLength(t)
    for k, _ in pairs(t) do
        if not isSequenceKey(k, sequenceLength) then
            table.insert(keys, k)
        end
    end
    table.sort(keys, sortKeys)
    return keys, sequenceLength
end

local function getToStringResultSafely(t, mt)
    local __tostring = type(mt) == 'table' and rawget(mt, '__tostring')
    local str, ok
    if type(__tostring) == 'function' then
        ok, str = pcall(__tostring, t)
        str = ok and str or 'error: ' .. tostring(str)
    end
    if type(str) == 'string' and #str > 0 then
        return str
    end
end

local function countTableAppearances(t, tableAppearances)
    tableAppearances = tableAppearances or {}

    if type(t) == 'table' then
        if not tableAppearances[t] then
            tableAppearances[t] = 1
            for k, v in pairs(t) do
                countTableAppearances(k, tableAppearances)
                countTableAppearances(v, tableAppearances)
            end
            countTableAppearances(getmetatable(t), tableAppearances)
        else
            tableAppearances[t] = tableAppearances[t] + 1
        end
    end

    return tableAppearances
end

local copySequence = function(s)
    local copy, len = {}, #s
    for i = 1, len do
        copy[i] = s[i]
    end
    return copy, len
end

local function makePath(path, ...)
    local keys = {...}
    local newPath, len = copySequence(path)
    for i = 1, #keys do
        newPath[len + i] = keys[i]
    end
    return newPath
end

local function processRecursive(process, item, path, visited)
    if item == nil then
        return nil
    end
    if visited[item] then
        return visited[item]
    end

    local processed = process(item, path)
    if type(processed) == 'table' then
        local processedCopy = {}
        visited[item] = processedCopy
        local processedKey

        for k, v in pairs(processed) do
            processedKey = processRecursive(process, k, makePath(path, k, inspect.KEY), visited)
            if processedKey ~= nil then
                processedCopy[processedKey] = processRecursive(process, v, makePath(path, processedKey), visited)
            end
        end

        local mt = processRecursive(process, getmetatable(processed), makePath(path, inspect.METATABLE), visited)
        setmetatable(processedCopy, mt)
        processed = processedCopy
    end
    return processed
end

-------------------------------------------------------------------

local Inspector = {}
local Inspector_mt = {__index = Inspector}

function Inspector:puts(...)
    local args = {...}
    local buffer = self.buffer
    local len = #buffer
    for i = 1, #args do
        len = len + 1
        buffer[len] = args[i]
    end
end

function Inspector:down(f)
    self.level = self.level + 1
    f()
    self.level = self.level - 1
end

function Inspector:tabify()
    self:puts(self.newline, string.rep(self.indent, self.level))
end

function Inspector:alreadyVisited(v)
    return self.ids[v] ~= nil
end

function Inspector:getId(v)
    local id = self.ids[v]
    if not id then
        local tv = type(v)
        id = (self.maxIds[tv] or 0) + 1
        self.maxIds[tv] = id
        self.ids[v] = id
    end
    return tostring(id)
end

function Inspector:putKey(k)
    if isIdentifier(k) then
        return self:puts(k)
    end
    self:puts('[')
    self:putValue(k)
    self:puts(']')
end

function Inspector:putTable(t)
    if t == inspect.KEY or t == inspect.METATABLE then
        self:puts(tostring(t))
    elseif self:alreadyVisited(t) then
        self:puts('<table ', self:getId(t), '>')
    elseif self.level >= self.depth then
        self:puts('{...}')
    else
        if self.tableAppearances[t] > 1 then
            self:puts('<', self:getId(t), '>')
        end

        local nonSequentialKeys, sequenceLength = getNonSequentialKeys(t)
        local mt = getmetatable(t)
        local toStringResult = getToStringResultSafely(t, mt)

        self:puts('{')
        self:down(
            function()
                if toStringResult then
                    self:puts(' -- ', escape(toStringResult))
                    if sequenceLength >= 1 then
                        self:tabify()
                    end
                end

                local count = 0
                for i = 1, sequenceLength do
                    if count > 0 then
                        self:puts(',')
                    end
                    self:puts(' ')
                    self:putValue(t[i])
                    count = count + 1
                end

                for _, k in ipairs(nonSequentialKeys) do
                    if count > 0 then
                        self:puts(',')
                    end
                    self:tabify()
                    self:putKey(k)
                    self:puts(' = ')
                    self:putValue(t[k])
                    count = count + 1
                end

                if mt then
                    if count > 0 then
                        self:puts(',')
                    end
                    self:tabify()
                    self:puts('<metatable> = ')
                    self:putValue(mt)
                end
            end
        )

        if #nonSequentialKeys > 0 or mt then -- result is multi-lined. Justify closing }
            self:tabify()
        elseif sequenceLength > 0 then -- array tables have one extra space before closing }
            self:puts(' ')
        end

        self:puts('}')
    end
end

function Inspector:putValue(v)
    local tv = type(v)

    if tv == 'string' then
        self:puts(smartQuote(escape(v)))
    elseif tv == 'number' or tv == 'boolean' or tv == 'nil' or tv == 'cdata' or tv == 'ctype' then
        self:puts(tostring(v))
    elseif tv == 'table' then
        self:putTable(v)
    else
        self:puts('<', tv, ' ', self:getId(v), '>')
    end
end

-------------------------------------------------------------------

function inspect.inspect(root, options)
    options = options or {}

    local depth = options.depth or math.huge
    local newline = options.newline or '\n'
    local indent = options.indent or '  '
    local process = options.process

    if process then
        root = processRecursive(process, root, {}, {})
    end

    local inspector =
        setmetatable(
        {
            depth = depth,
            level = 0,
            buffer = {},
            ids = {},
            maxIds = {},
            newline = newline,
            indent = indent,
            tableAppearances = countTableAppearances(root)
        },
        Inspector_mt
    )

    inspector:putValue(root)

    return table.concat(inspector.buffer)
end

setmetatable(
    inspect,
    {
        __call = function(_, ...)
            return inspect.inspect(...)
        end
    }
)

return inspect