pretty/pretty.lua

--[[-- # Pretty

`pretty` is an advanced pretty printer for [Lua](https://lua.org). It's primarily a
debugging tool, aiming for human readability, by detecting pattern in the input
data, and creating an output string utilizing and highlighting those patterns.

## Code Example

Setup is simple, use `pretty = require 'pretty'`, and you're good to go.

```lua
$ print(pretty( { 1, 2, 3 } ))
{ 1, 2, 3 }

$ print(pretty( { hello = 'world', num = 42 } ))
{
    num   = 42
    hello = 'world'
}

$ print(pretty( { abs = math.abs, max = math.max, some = function() end } ))
{
    abs  = builtin function (x)      ... end
    max  = builtin function (x, ...) ... end
    some =         function ()       ... end
}

$ print(pretty( math.abs ))
builtin function (x)
    -- math.abs
    -- Returns the absolute value of x

    ...
end
```

## Motivation

This project is the outcome of my frustration with existing pretty printers, and
a desire to expand upon the pretty printer I developed for
[Xenoterm](https://gitfub.space/takunomi/Xenoterm). The original Xenoterm pretty
printer was much simpler than `pretty` - and the current is even simpler - but
the enhancements I make, when compared to other pretty printers, inspired me to
create `pretty`.

`pretty` sorts it's priorities like so:

1.    Human readability.
2.    Lua-compatible output.
3.    Customization.

I'd rather have good defaults than provide a ton of customization options. If an
structure avoids easy representation in Lua, I'd rather extend the syntax, than
lose the info.

Another aspect where `pretty` shines is in exploratory programming, when
attempting to avoid reliance on outside documentation. The amount of information
`pretty` exposes varies by the data you are inspecting. If you're inspecting
a list of functions, their function signatures are visible, but if you're
inspecting a single function, documentation and source location may appear if
available.

## Features

- Written in good-old pure-blood Lua, with support for PUC Lua 5.0+ and LuaJIT 2.0+.
- Redefining what it means to be "human readable":
 * Is multi-line centric, to aid readability.
 * Indention and alignment of keys-value pairs.
 * Keys-value pairs are
 [alpha-numerically](http://www.davekoelle.com/alphanum.html) sorted by key
 type and thereafter alphabetically.
 * The format and structure of output changes depending upon the input.  Maps
 appear differently to deeply nested tables to long sequences with short
 strings to short lists.
 * Uses the standard `debug` library to gain information about functions and
 other advanced structures.

## Installation

`pretty` is loadable directly with `require`. Either clone or download this
repository. Where you place it, depends upon what you want to do:

1.  **You want `pretty` in a specific project**: Place the `pretty` folder
somewhere in your project, and `require` it from one of your project files.
2.  **You want `pretty` on your system**: Place the `pretty` folder such that
it's visible from your Lua-path. On my system this might be
`/usr/local/share/lua/5.1/`. Now you can `require` it from anywhere.

## API Documentation

`pretty` exposes a single function, the `pretty` function itself. It's function
signature is `pretty(value, options)`. `value` can be any Lua value. `options`
must be a table.

### List of options

`pretty` is sure to complain if you give it an unknown option, or if you give an
option a bad value.

- `indent: string`: The string to indent with. Four spaces by default.

## TODO

Tasks to be done before `pretty` can be called version 1.0.0, in order of
priority:

- [ ] Add dedicated unicode submodule, to handle some minor alignment and
character escaping issues. `pretty` should escape all malformed unicode
sequences.
- [ ] Align numbers towards right for tabular views.
- [ ] Add support for `setmetatable`, and exploring values in metatables.
- [ ] Provide nice formatting for `cdata` datatype in LuaJIT.
- [ ] Find a better name than `pretty`.
- [ ] Enhance internal structure some amount. See `TODO` markers in files.

It would be nice to have the following, but these are secondary:

- [ ] Add option for colored output. Primarily syntax highlighting, but also
[BlueJ-style](www.bluej.org/about.html) scope highlighting, with some faint
background colors.
- [ ] Expand on the comment output in output, for `__tostring` methods, and
global namespaces like `io` or `math`.
- [ ] Fit output within a predefined width limit. Default to 80.
- [ ] Look into tool for understanding complex structures with recursive
definitions. Whatever modes are thought up, they should be automatic modes, not
an options. Should at least include modes for self-referential tables and
Directed-Acyclic-Graphs.

## Alternative pretty printers

`pretty` is large, slow, and requires the debug library to work. It's not
designed for serialization purposes, nor is it concerned with offering the same
level of customization as other libraries do.

If you want a sleek, fast, customizable or embeddable library, there are
thankfully other options.

- [inspect.lua](github.com/kikito/inspect.lua): One of the classic debugging pretty printers.
- [pprint.lua](github.com/jagt/pprint.lua): Reimplementation of `inspect.lua`
- [serpent](github.com/pkulchenko/serpent): Advanced and fast pretty printer.
- [pluto](lua-users.org/wiki/PlutoLibrary): Can serialize arbitrary parts of
Lua, including functions, upvalues, and proper lexical scoping. Not written in
native Lua.
- [binser](github.com/bakpakin/binser): Library for special purpose serialization.

Even more are available at [the lua-users wiki](lua-users.org/wiki/TableSerialization).

## Thoughts on displaying tables in an intuitive way.

Lua's table data-structure is likely to be the most concise data structure ever
invented. (If not, please send me a link!) Lists, maps, objects, classes,
proxies, etc. This obviously brings about it some difficulty when attempting to
represent these tables. What do we want to highlight, and what do we choose to
avoid?

One notable issue is whether to show every key that a table answers (to lift
some Smalltalk terms) to, or to just display those it contains. That is, do we
think about `__index` in the table's metatable and what it returns, or do we
ignore `__index`? For cases where `__index` is a function, we cannot say
anything about the keys that the table answers to. If `__index` is a table, we
have a better idea, but it would be cluttered to display both types of keys side
by side.

1.  Native representation: Lua's native representation includes the type and
address of the table. It allows for distinguishing between unique tables,
but won't tell us anything about the contents.
2.  Omission: By representing tables as the pseudo-parsable `{...}`, it's
clear we are talking about a table. We disregard the ability to
distinguish between tables.
2.  If the table is empty, we could represent it as `{}`. But what if the table
has a metatable with `__index` defined? We could continue to represent it as
`{}`, but `{...}` would be more "honest".
3.  Single-line: TODO
4.  Multi-line: TODO
5.  Columns: For some highly-regular structures, like lists of short strings,
giving each string it's own line would be too long, but formatting them as a
single-line list would be too cluttered. Thus we can take inspiration from
the classic `ls` unix tool, and place the output into columns, to help guide
the eyes.
6.  Tabular: Other structures are formatted like actual tables of data, e.g. a
sequence of tuples, like one would see in an SQL database. For these
structures it's an obvious choice to align them based on the keys.
7.  Pseudo-Tabular: Some structures are almost tabular, e.g. they are sequences
of tuples, but some of the tuples differ in their structure. For these
structures it's still useful to tabulate the keys that all tuples share. To
do this we should sort the key order descending by the number of tuples with
the key.
But what do we do about the the outlier keys? We can either justify the
entire table, and give specific spots for the outlier keys, thereby
significantly increasing the size of the table, or we can leave the table
unjustified, abandoning it's eye-guiding attributes.
8.  Special cases: (Array-tree, Table-Tree, Linked-List, Predictive Sequences) TODO
--]]

--------------------------------------------------------------------------------
-- Import files

local import
do
    local this_path = ... and select('1', ...):match('.+%.') or ''
    import = function (name, ignore_failure)  return require(this_path..name)  end
end

--------------------------------------------------------------------------------
-- Constants

local ERROR_UNKNOWN_TYPE = [[
[pretty]: Attempting to format unsupported value of type "%s".
    A native formatting of the value is: %s

We are attempting to cover all Lua features, so please report this bug, so we can improve.
]]

local TERMINAL_WIDTH = 80
local MAX_WIDTH_FOR_SINGLE_LINE_TABLE = 38

if io and io.popen then
    local f = io.popen "tput cols"
    local term_width = f:read '*n'
    f:close()
    if term_width then
        TERMINAL_WIDTH = term_width
        --MAX_WIDTH_FOR_SINGLE_LINE_TABLE = term_width * (2 / 3)
    end
end

local KEY_TYPE_SORT_ORDER = {
    ['number']   = 0,
    ['string']   = 1,
    ['boolean']  = 2,
    ['table']    = 3,
    ['userdata'] = 4,
    ['thread']   = 5,
    ['function'] = 6,
}

local VALUE_TYPE_SORT_ORDER = {
    ['nil']      = 0,
    ['boolean']  = 1,
    ['number']   = 2,
    ['string']   = 3,
    ['table']    = 4,
    ['userdata'] = 5,
    ['thread']   = 6,
    ['function'] = 7,
}

local COLUMN_SEPERATION = 1

--------------------------------------------------------------------------------
-- Key-value-pair Util

local function padnum(minus, dec, zeroes, n)
    return dec == '.' and ("%.12f"):format(dec..zeroes..n) or ("%s%03d%s"):format(minus == '' and ':' or minus, #n, n)
end

local function alphanum_compare_strings (a, b)
    -- Compares two strings alphanumerically.

    assert(type(a) == 'string')
    assert(type(b) == 'string')

    local a_padded  =  a:gsub("(%-?)(%.?)(0*)(%d+)", padnum)..("\0%3d"):format(#b)
    local b_padded  =  b:gsub("(%-?)(%.?)(0*)(%d+)", padnum)..("\0%3d"):format(#a)
    -- Correction for sorting of negative numbers:
    if a_padded:sub(1,1) == '-' and b_padded:sub(1,1) == '-' then
        a_padded, b_padded = b_padded, a_padded
    end
    --
    local A_padded, B_padded  =  a_padded:upper(), b_padded:upper()
    if A_padded == B_padded then  return  a_padded < b_padded  end
    return A_padded < B_padded
end

local function compare_key_value_pair (a, b)
    -- Function for comparing two key-value pairs, given as `{ key, value }`.
    -- Pretty complex due to our high standards for sorting.

    assert(type(a) == 'table')
    assert(type(b) == 'table')

    -- Get types
    local type_key_a,   type_key_b   = type(a[1]), type(b[1])
    local type_value_a, type_value_b = type(a[2]), type(b[2])

    -- Tons of compare
    if (1 == (type_key_a == 'number' and 1 or 0) + (type_key_b == 'number' and 1 or 0)) then
        return type_key_a == 'number'
    elseif (type_key_a == 'number' and type_key_b == 'number') then
        return a[1] < b[1]
    elseif (type_value_a ~= type_value_b) then
        return VALUE_TYPE_SORT_ORDER[type_value_a] < VALUE_TYPE_SORT_ORDER[type_value_b]
    elseif (type_key_a == 'string' and type_key_b == 'string') then
        return alphanum_compare_strings(a[1], b[1])
    elseif (type_key_a ~= type_key_b) then
        return KEY_TYPE_SORT_ORDER[type_value_a] < KEY_TYPE_SORT_ORDER[type_value_b]
    end
end

local function get_key_value_pairs_in_proper_order (t)
    -- Generates a sequence of key value pairs, in proper order.
    -- Proper order is:
    -- 1. All integer keys are first, in order
    -- 2. Then by value type, as defined in  VALUE_TYPE_SORT_ORDER in the top.
    -- 3. Then by key type.
    -- 3.1. String in alphanumeric order
    -- 3.2. Other wierdness.

    -- Error checking
    assert(type(t) == 'table')

    -- Find Key-Value Pairs
    local kv_pairs = {}
    for key, value in pairs(t) do  kv_pairs[#kv_pairs+1] = { key, value }  end

    -- Sort them into the correct order
    table.sort(kv_pairs, compare_key_value_pair)

    -- Return them
    return kv_pairs
end

local function fill_holes_in_key_value_pairs (kv_pairs)
    -- Fills holes in key-value pairs for a sequences with `nil` values. All
    -- keys must be numbers, and key-value pairs must be sorted already.

    -- Holes can sometimes appear in otherwise nicely structured sequences. We
    -- want to avoid displaying a sequence as `{[1] = 1, [3] = 3}` when
    -- `{1, nil, 3}` would work nicely.

    -- Error checking
    assert(type(kv_pairs) == 'table')

    -- Add hole filling value
    assert(type(kv_pairs[1][1]) == 'number')
    for i = 2, #kv_pairs do
        assert(type(kv_pairs[i][1]) == 'number')
        for j = kv_pairs[i-1][1] + 1, kv_pairs[i][1] - 1 do
            kv_pairs[#kv_pairs+1] = { j, nil }
        end
    end

    -- Sort key-value pairs, to place above pairs into their correct locations.
    table.sort(kv_pairs, compare_key_value_pair)
end

--------------------------------------------------------------------------------
-- Formatting Util

local length_of_utf8_string  =  import 'common' . utf8_string_length
local width_of_strings_in_l  =  import 'common' . width_of_strings_in_l

local function ignore_alignment_info (l, start_i, stop_i)

    -- Argument fixing and Error Checking
    assert(type(l) == 'table')

    local start_i, stop_i = start_i or 1, stop_i or #l

    assert(type(start_i) == 'number')
    assert(type(stop_i)  == 'number')

    -- Do stuff
    for i = start_i, stop_i do
        if type(l[i]) == 'table' and l[i][1] == 'align' then
            l[i] = ''
        end
    end
end

local function insert_alignment_estimations (l, start_i, stop_i)
    -- Argument fixing and Error Checking
    assert(type(l) == 'table')

    local start_i, stop_i = start_i or 1, stop_i or #l

    assert(type(start_i) == 'number')
    assert(type(stop_i)  == 'number')

    -- Find maximums
    local max  =  {}
    for i = start_i, stop_i do
        if type(l[i]) == 'table' and l[i][1] == 'align' then
            max[ l[i][2] ]  =  math.max( l[i][3], max[ l[i][2] ] or 0 )
        end
    end

    -- Insert the proper whitespace
    for i = start_i, stop_i do
        if type(l[i]) == 'table' and l[i][1] == 'align' then
            l[i].est_width = max[ l[i][2] ] - l[i][3]
        end
    end
end

local function fix_alignment (l, start_i, stop_i)

    -- Argument fixing and Error Checking
    assert(type(l) == 'table')

    local start_i, stop_i = start_i or 1, stop_i or #l

    assert(type(start_i) == 'number')
    assert(type(stop_i) == 'number')

    -- Find whitespace to insert
    insert_alignment_estimations(l, start_i, stop_i)

    -- Insert whitespace
    for i = start_i, stop_i do
        if type(l[i]) == 'table' and l[i][1] == 'align' then
            l[i] = string.rep(' ', l[i].est_width)
        end
    end
end

local function attempt_to_align_into_columns (l, start_i, stop_i, nr_items_pr_row)
    assert(type(l) == 'table')
    assert(type(start_i) == 'number')
    assert(type(stop_i)  == 'number')
    assert(type(nr_items_pr_row) == 'number')

    local column = {}
    ---
    local start_of_item_i, item_nr  =  nil, 0
    for i = start_i, stop_i do
        if type(l[i]) == 'table' and (l[i][1] == 'indent' or l[i][1] == 'seperator' or l[i][1] == 'unindent') then
            if start_of_item_i then
                local width_of_item = width_of_strings_in_l(l, start_of_item_i, i-1)
                local column_i = (item_nr-1)%nr_items_pr_row+1
                column[column_i]  =  math.max(column[column_i] or 0, width_of_item)
            end
            start_of_item_i, item_nr  =  i + 1, item_nr + 1
        end
    end
    ---
    local width  =  nr_items_pr_row * 2 - 1  -- FIXME: Magic numbers: 2 = #', ', 1 = #' '
    for i = 1, #column do  width = width + column[i]  end
    --
    return width, column
end

local function align_into_columns (l, start_i, stop_i)

    -- Argument fixing and Error Checking
    assert(type(l) == 'table')

    local start_i, stop_i = start_i or 1, stop_i or #l

    assert(type(start_i)    == 'number')
    assert(type(stop_i)    == 'number')

    insert_alignment_estimations(l, start_i, stop_i)

    -- Find columns
    local columns = nil
    for nr_items_pr_row = 10, 1, -1 do  -- TODO: Do this more intelligently.
        local column_width
        column_width, columns  =  attempt_to_align_into_columns(l, start_i, stop_i, nr_items_pr_row)
        if column_width <= l.options.max_width_for_single_line_table then  break  end
    end

    -- Change alignment of columns
    local start_of_item_i, item_nr  =  nil, 0
    for i = start_i, stop_i do
        if type(l[i]) == 'table' and l[i][1] == 'align' then
            local column_i = (item_nr-1)%#columns+1
            l[i][2] = l[i][2] .. '_column_'..column_i
        elseif (l[i][1] == 'indent' or l[i][1] == 'seperator' or l[i][1] == 'unindent') then
            start_of_item_i, item_nr  =  i + 1, item_nr + 1
        end
    end

    -- Fix newly changed alignment
    fix_alignment(l, start_i, stop_i)

    -- Quick-exit on only a single column
    if #columns == 1 then  return  end

    -- Fit into columns.
    local start_of_item_i, item_nr  =  nil, 0
    for i = start_i, stop_i do
        if type(l[i]) ~= 'table' then
            -- Do nothing
        elseif (l[i][1] == 'indent' or l[i][1] == 'seperator' or l[i][1] == 'unindent') then
            if start_of_item_i and l[i][1] == 'seperator' then
                local column_i = (item_nr-1)%#columns+1
                if column_i ~= #columns then
                    local width_of_item = width_of_strings_in_l(l, start_of_item_i, i-1)
                    l[i] = l[i][2] .. (' '):rep(COLUMN_SEPERATION+columns[column_i]-width_of_item)
                end
            end
            start_of_item_i, item_nr  =  i + 1, item_nr + 1
        end
    end
end

local function align_into_tabular_style (l, start_i, stop_i)
    -- Adds alignment after separators, to create nicely aligned tabular-format.

    -- Argument fixing and Error Checking
    local start_i, stop_i = start_i or 1, stop_i or #l

    assert(type(l)             == 'table')
    assert(type(start_i)       == 'number')
    assert(type(stop_i)        == 'number')
    assert(type(l[start_i])    == 'table' and l[start_i][1]    == 'indent')
    assert(type(l[stop_i])     == 'table' and l[stop_i][1]     == 'unindent')

    -- Calculate where to insert new alignment.
    local indent, key_nr, index_of_last_meta, insert_later  =  0, 0, 1, {}
    for i = start_i + 1, stop_i - 1 do
        if type(l[i]) ~= 'table' then
            -- Do nothing
        elseif l[i][1] == 'indent' then
            indent =  indent + 1
            if indent == 1 then  key_nr = 1  end
            index_of_last_meta = i
        elseif l[i][1] == 'unindent' then
            insert_later[#insert_later+1] = {'align', 'end_subtable_'..key_nr, width_of_strings_in_l(l, index_of_last_meta+1, i), i}
            index_of_last_meta, key_nr  =  i, key_nr + 1
            indent =  indent - 1
        elseif l[i][1] == 'seperator' and indent ~= 0 then
            insert_later[#insert_later+1] = {'align', 'key_'..key_nr, width_of_strings_in_l(l, index_of_last_meta+1, i), i+1}
            index_of_last_meta, key_nr  =  i, key_nr + 1
        end
    end
    -- Insert new alignment.
    for i = #insert_later, 1, -1 do
        local dat = insert_later[i]
        table.insert(l, dat[#dat], dat)
        dat[#dat] = nil
    end
    -- Fix that alignemnt
    return fix_alignment(l, start_i)
end

local function fix_seperator_info (l, indent_char)

    -- Error Checking
    assert(type(l) == 'table')
    assert(type(indent_char) == 'string')
    -- Do stuff

    local display, inline_depth = 0, nil
    for i = 1, #l do
        if type(l[i]) ~= 'table' then
            -- Do nothing
        elseif l[i][1] == 'seperator' then
            assert(l[i][2] == nil or type(l[i][2]) == 'string')
            l[i]  =  (l[i][2] or '') .. (inline_depth and ' ' or ('\n' .. indent_char:rep(display)))
        elseif l[i][1] == 'indent' then
            display, inline_depth  =  display + 1, inline_depth or l[i][3] == 'inline' and display + 1 or nil
            l[i] = l[i][2] .. (inline_depth and ' ' or ('\n' .. indent_char:rep(display)))
        elseif l[i][1] == 'unindent' then
            l[i] = (inline_depth and ' ' or ('\n' .. indent_char:rep(display-1))) .. l[i][2]
            display, inline_depth  =  display - 1, (display ~= inline_depth) and inline_depth or nil
        end
    end
end

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

local analyze_structure    =  import 'analyze_structure'
local TABLE_TYPE           =  import 'common' . TABLE_TYPE
local DISPLAY              =  import 'common' . DISPLAY

--------------------------------------------------------------------------------
-- Key-value pair formatting.

local function format_key_and_value_string_map (key, value, display, l, format_value)
    l[#l+1] = key
    l[#l+1] = { 'align', 'key', length_of_utf8_string(key) }
    l[#l+1] = ' = '
    return format_value(value, display, l)
end

local function format_key_and_value_arbitr_map (key, value, display, l, format_value)
    local index_before_key = #l+1
    l[#l+1] = '['
    format_value(key, DISPLAY.HIDE, l)
    l[#l+1] = ']'
    l[#l+1] = { 'align', 'key', width_of_strings_in_l(l, index_before_key) }
    l[#l+1] = ' = '
    return format_value(value, display, l)
end

local function format_key_and_value_sequence (key, value, display, l, format_value)
    return format_value(value, display, l)
end

local TABLE_TYPE_TO_PAIR_FORMAT = {
    [TABLE_TYPE.EMPTY]      = format_key_and_value_sequence,
    [TABLE_TYPE.SEQUENCE]   = format_key_and_value_sequence,
    [TABLE_TYPE.SET]        = format_key_and_value_arbitr_map,
    [TABLE_TYPE.MIXED]      = format_key_and_value_arbitr_map,
    [TABLE_TYPE.STRING_MAP] = format_key_and_value_string_map,
    [TABLE_TYPE.PURE_MAP]   = format_key_and_value_arbitr_map,
}

-------------------------------------------------------------------------------
-- Table formatting

local function format_table (t, display, l, format_value)
    -- Error Checking
    assert(type(t) == 'table')
    assert(type(display) == 'number' and type(l) == 'table')

    -- Find table info
    if not l.info[t] then  analyze_structure(t, display, l.info)  end
    local table_info  =  l.info[t]
    assert(table_info)

    -- If empty or not a lot of space, give a small represetation: `{...}`
    if table_info.type == TABLE_TYPE.EMPTY or display <= DISPLAY.SMALL then
        l '{'
        if l.options._table_addr_comment       then  l[#l+1] = ' --[[' .. table_info.address .. ']] '  end
        if table_info.type ~= TABLE_TYPE.EMPTY then  l[#l+1] = '...'  end
        return l '}'
    end

    -- Get key-value pairs, and possibly fill holes.
    local key_value_pairs  = get_key_value_pairs_in_proper_order(t)
    if table_info.type == TABLE_TYPE.SEQUENCE and l.info[t].has_holes then
        fill_holes_in_key_value_pairs(key_value_pairs)
    end

    -- Find pair formatting function
    local pair_format_func = TABLE_TYPE_TO_PAIR_FORMAT[table_info.type]
    local start_of_table_i = #l + 1
    assert(pair_format_func)

    -- Begin formatting table.
    local next_display  =  display - 1
    if (l.info[t].value_types.nr_types >= 2) then  next_display = DISPLAY.SMALL  end

    l[#l+1] = {'indent', '{'}
    if l.options._table_addr_comment then  l[#l+1], l[#l+2]  =  '--[['..table_info.address..']]', {'seperator'}  end
    for _, pair in ipairs(key_value_pairs) do
        pair_format_func(pair[1], pair[2], next_display, l, format_value)
        l[#l+1] = {'seperator', ','}
    end
    if l[#l][1] == 'seperator' then  l[#l] = nil  end
    l[#l+1] = {'unindent', '}'}

    -- Decide for short or long table formatting.
    local table_width  =  width_of_strings_in_l(l, start_of_table_i)

    if table_width <= l.options.max_width_for_single_line_table then
        -- Is short table: Ignore "width of key".
        l[start_of_table_i][3] = 'inline'
        ignore_alignment_info(l, start_of_table_i)
    elseif table_info.is_leaf_node then
        -- Is leaf node: Can format into columns.
        -- Only if long or sequence.
        -- NOTE: Currently we only allow leaf-nodes to format into columns, due
        -- to issues with table alignment.
        align_into_columns(l, start_of_table_i)
    elseif table_info.is_tabular then
        align_into_tabular_style(l, start_of_table_i, #l)
    else
        -- Is long table: Fix whitespace alignment
        fix_alignment(l, start_of_table_i)
    end
end

-------------------------------------------------------------------------------
-- Coroutine formatting

local function format_coroutine (value, _, l)
    -- Formats a coroutine. Unfortunantly we cannot gather a lot of information
    -- about coroutines.

    -- Error check
    assert(type(value) == 'thread')
    assert(type(l) == 'table')

    -- Do stuff
    l[#l+1] = coroutine.status(value)
    l[#l+1] = ' coroutine: '
    l[#l+1] = tostring(value):sub(9)
end

-------------------------------------------------------------------------------
-- Primitive formatting

local function format_primitive (value, _, l)
    -- Error check
    assert(type(l) == 'table')
    -- Do stuff
    l[#l+1] = tostring(value)
end

local TYPE_TO_FORMAT_FUNC = {
    ['nil']      =  format_primitive,
    ['boolean']  =  format_primitive,
    ['number']   =  import 'number',
    ['string']   =  import 'pstring',
    ['thread']   =  format_coroutine,
    ['table']    =  format_table,
    ['function'] =  import 'function',

    -- TODO
    ['userdata'] =  format_primitive,
    ['cdata']    =  import 'cdata',     -- Luajit exclusive ?
}

local function format_value (value, display, l)
    assert(type(display) == 'number' and type(l) == 'table')
    local formatting = TYPE_TO_FORMAT_FUNC[type(value)]
    if formatting then
        formatting(value, display, l, format_value)
    else
        error(ERROR_UNKNOWN_TYPE:format(type(value), tostring(value)), 2)
    end
end

--------------------------------------------------------------------------------
-- StringBuilder

local StringBuilder = {}
      StringBuilder.__index = StringBuilder
      StringBuilder.__call  = function (l, s) l[#l+1] = s end
setmetatable(StringBuilder, {
    __call = function() return setmetatable({}, StringBuilder) end
})

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

local DEBUG_OPTION_USED = {  }

local KNOWN_OPTIONS = {
    _table_addr_comment = { type = 'boolean', default = false, debug = 'debug' }, -- TODO: Maybe automatically display table address when display = 0?

    indent              = { type = 'string',  default = '    ' },

    max_output_width    = { type = 'number',  default = TERMINAL_WIDTH }
}

local function ensure_that_all_options_are_known (input_options)
    -- Goes through all the given options, throws error if one is unknown, gives
    -- warning if debug or experimental. Creates a clone of the given table, to
    -- avoid defaults leaking.

    -- Error check that options were table
    assert(type(input_options) == 'table')

    -- Error check options
    for option_name, option_value in pairs(input_options) do
        if not KNOWN_OPTIONS[option_name] then
            error(('[pretty]: Unknown option: %s. Was given value %s (%s)'):format(option_name, option_value, type(option_value)), 2)
        elseif type(option_value) ~= KNOWN_OPTIONS[option_name].type then
            error(('[pretty]: Bad value given to option %s: %s (%s). Expected value of type %s'):format(option_name, option_value, type(option_value), KNOWN_OPTIONS[option_name].type), 2)
        elseif KNOWN_OPTIONS[option_name].accepted and not KNOWN_OPTIONS[option_name].accepted[option_value] then
            error(('[pretty]: Bad value given to option %s: %s (%s).'):format(option_name, option_value, type(option_value)), 2)
        elseif KNOWN_OPTIONS[option_name].debug and not DEBUG_OPTION_USED[option_name] then
            DEBUG_OPTION_USED[option_name] = true
            print(('[pretty]: Using %s option "%s".\n    Please note that this option may change at any time. It is not stable,\n    not tested, and may indeed break or be removed without warning.'):format(KNOWN_OPTIONS[option_name].debug, option_name))
        end
    end

    -- Create output options
    local output_options = {}
    -- Assign default values
    for option_name, option_info in pairs(KNOWN_OPTIONS) do
        if input_options[option_name] ~= nil then
            output_options[option_name] = input_options[option_name]
        else
            output_options[option_name] = option_info.default
        end
    end
    -- Calculate derived settings
    output_options.max_width_for_single_line_table = MAX_WIDTH_FOR_SINGLE_LINE_TABLE -- TODO: Make dynamic

    -- Returns input_options
    return output_options
end

local function length_of_longest_line_in_text (text)
    assert(type(text) == 'string')
    local longest_line_len = text:match '([^\n]*)$' : len()
    for line in text:gmatch '(.-)\n' do
        longest_line_len = math.max(longest_line_len, line:len())
    end
    return longest_line_len
end

local function internal_warning (fmt, ...)
    io.stderr:write('[pretty/internal]: '..string.format(fmt, ...))
end

local function assert_pretty_result (repr, options)
    assert(type(repr) == 'string')
    assert(type(options) == 'table')
    -- Determine length of longest line in output
    local max_width = length_of_longest_line_in_text(repr)
    if max_width > options.max_output_width then
        internal_warning('Internal assertion failed. Width of output was %i, but should be less than %i.', max_width, options.max_output_width)
    end
end

local function pretty_format (value, options)
    -- Error checking
    local options  =  ensure_that_all_options_are_known(options or {})

    -- Setup StringBuilder
    local l = StringBuilder()
          l.options = options
          l.info    = analyze_structure(value, 3)

    -- Format value.
    format_value(value, DISPLAY.EXPAND, l)

    -- If any alignment info still exists, ignore it
    fix_seperator_info(l, l.options.indent)
    ignore_alignment_info(l)

    -- Concat and perform last assertions.
    local repr = table.concat(l, '')
    assert_pretty_result(repr, options)

    -- Return
    return repr
end

return pretty_format