# This file is a part of Julia. License is MIT: https://julialang.org/license

# Text / HTML objects

import Base: print, show, ==, hash

export HTML, @html_str

export HTML, Text, apropos

"""
`HTML(s)`: Create an object that renders `s` as html.

    HTML("<div>foo</div>")

You can also use a stream for large amounts of data:

    HTML() do io
      println(io, "<div>foo</div>")
    end
"""
mutable struct HTML{T}
    content::T
end

function HTML(xs...)
    HTML() do io
        for x in xs
            show(io, MIME"text/html"(), x)
        end
    end
end

show(io::IO, ::MIME"text/html", h::HTML) = print(io, h.content)
show(io::IO, ::MIME"text/html", h::HTML{<:Function}) = h.content(io)

"""
    @html_str -> Docs.HTML

Create an `HTML` object from a literal string.
"""
macro html_str(s)
    :(HTML($s))
end

function catdoc(xs::HTML...)
    HTML() do io
        for x in xs
            show(io, MIME"text/html"(), x)
        end
    end
end

export Text, @text_str

"""
`Text(s)`: Create an object that renders `s` as plain text.

    Text("foo")

You can also use a stream for large amounts of data:

    Text() do io
      println(io, "foo")
    end
"""
mutable struct Text{T}
    content::T
end

print(io::IO, t::Text) = print(io, t.content)
print(io::IO, t::Text{<:Function}) = t.content(io)
show(io::IO, t::Text) = print(io, t)

==(t1::T, t2::T) where {T<:Union{HTML,Text}} = t1.content == t2.content
hash(t::T, h::UInt) where {T<:Union{HTML,Text}} = hash(T, hash(t.content, h))

"""
    @text_str -> Docs.Text

Create a `Text` object from a literal string.
"""
macro text_str(s)
    :(Text($s))
end

function catdoc(xs::Text...)
    Text() do io
        for x in xs
            show(io, MIME"text/plain"(), x)
        end
    end
end

# REPL help

function helpmode(io::IO, line::AbstractString)
    line = strip(line)
    expr =
        if haskey(keywords, Symbol(line))
            # Docs for keywords must be treated separately since trying to parse a single
            # keyword such as `function` would throw a parse error due to the missing `end`.
            Symbol(line)
        else
            x = Base.syntax_deprecation_warnings(false) do
                parse(line, raise = false)
            end
            # Retrieving docs for macros requires us to make a distinction between the text
            # `@macroname` and `@macroname()`. These both parse the same, but are used by
            # the docsystem to return different results. The first returns all documentation
            # for `@macroname`, while the second returns *only* the docs for the 0-arg
            # definition if it exists.
            (isexpr(x, :macrocall, 1) && !endswith(line, "()")) ? quot(x) : x
        end
    # the following must call repl(io, expr) via the @repl macro
    # so that the resulting expressions are evaluated in the Base.Docs namespace
    :(Base.Docs.@repl $io $expr)
end
helpmode(line::AbstractString) = helpmode(STDOUT, line)

function repl_search(io::IO, s)
    pre = "search:"
    print(io, pre)
    printmatches(io, s, completions(s), cols = displaysize(io)[2] - length(pre))
    println(io, "\n")
end
repl_search(s) = repl_search(STDOUT, s)

function repl_corrections(io::IO, s)
    print(io, "Couldn't find ")
    Markdown.with_output_format(:cyan, io) do io
        println(io, s)
    end
    print_correction(io, s)
end
repl_corrections(s) = repl_corrections(STDOUT, s)

# inverse of latex_symbols Dict, lazily created as needed
const symbols_latex = Dict{String,String}()
function symbol_latex(s::String)
    if isempty(symbols_latex)
        for (k,v) in Base.REPLCompletions.latex_symbols
            symbols_latex[v] = k
        end
    end
    return get(symbols_latex, s, "")
end
function repl_latex(io::IO, s::String)
    latex = symbol_latex(s)
    if !isempty(latex)
        print(io, "\"")
        Markdown.with_output_format(:cyan, io) do io
            print(io, s)
        end
        print(io, "\" can be typed by ")
        Markdown.with_output_format(:cyan, io) do io
            print(io, latex, "<tab>")
        end
        println(io, '\n')
    elseif any(c -> haskey(symbols_latex, string(c)), s)
        print(io, "\"")
        Markdown.with_output_format(:cyan, io) do io
            print(io, s)
        end
        print(io, "\" can be typed by ")
        Markdown.with_output_format(:cyan, io) do io
            for c in s
                cstr = string(c)
                if haskey(symbols_latex, cstr)
                    print(io, symbols_latex[cstr], "<tab>")
                else
                    print(io, c)
                end
            end
        end
        println(io, '\n')
    end
end
repl_latex(s::String) = repl_latex(STDOUT, s)

macro repl(ex) repl(ex) end
macro repl(io, ex) repl(io, ex) end

function repl(io::IO, s::Symbol)
    str = string(s)
    quote
        repl_latex($io, $str)
        repl_search($io, $str)
        ($(isdefined(s) || haskey(keywords, s))) || repl_corrections($io, $str)
        $(_repl(s))
    end
end
isregex(x) = isexpr(x, :macrocall, 2) && x.args[1] === Symbol("@r_str") && !isempty(x.args[2])
repl(io::IO, ex::Expr) = isregex(ex) ? :(apropos($io, $ex)) : _repl(ex)
repl(io::IO, str::AbstractString) = :(apropos($io, $str))
repl(io::IO, other) = :(@doc $(esc(other)))

repl(x) = repl(STDOUT, x)

function _repl(x)
    if (isexpr(x, :call) && !any(isexpr(x, :(::)) for x in x.args))
        x.args[2:end] = [:(::typeof($arg)) for arg in x.args[2:end]]
    end
    docs = :(@doc $(esc(x)))
    if isfield(x)
        quote
            if isa($(esc(x.args[1])), DataType)
                fielddoc($(esc(x.args[1])), $(esc(x.args[2])))
            else
                $docs
            end
        end
    else
        docs
    end
end


# Search & Rescue
# Utilities for correcting user mistakes and (eventually)
# doing full documentation searches from the repl.

# Fuzzy Search Algorithm

function matchinds(needle, haystack; acronym = false)
    chars = collect(needle)
    is = Int[]
    lastc = '\0'
    for (i, char) in enumerate(haystack)
        isempty(chars) && break
        while chars[1] == ' ' shift!(chars) end # skip spaces
        if lowercase(char) == lowercase(chars[1]) && (!acronym || !isalpha(lastc))
            push!(is, i)
            shift!(chars)
        end
        lastc = char
    end
    return is
end

longer(x, y) = length(x) ≥ length(y) ? (x, true) : (y, false)

bestmatch(needle, haystack) =
    longer(matchinds(needle, haystack, acronym = true),
           matchinds(needle, haystack))

avgdistance(xs) =
    isempty(xs) ? 0 :
    (xs[end] - xs[1] - length(xs)+1)/length(xs)

function fuzzyscore(needle, haystack)
    score = 0.
    is, acro = bestmatch(needle, haystack)
    score += (acro?2:1)*length(is) # Matched characters
    score -= 2(length(needle)-length(is)) # Missing characters
    !acro && (score -= avgdistance(is)/10) # Contiguous
    !isempty(is) && (score -= mean(is)/100) # Closer to beginning
    return score
end

function fuzzysort(search, candidates)
    scores = map(cand -> (fuzzyscore(search, cand), -levenshtein(search, cand)), candidates)
    candidates[sortperm(scores)] |> reverse
end

# Levenshtein Distance

function levenshtein(s1, s2)
    a, b = collect(s1), collect(s2)
    m = length(a)
    n = length(b)
    d = Matrix{Int}(m+1, n+1)

    d[1:m+1, 1] = 0:m
    d[1, 1:n+1] = 0:n

    for i = 1:m, j = 1:n
        d[i+1,j+1] = min(d[i  , j+1] + 1,
                         d[i+1, j  ] + 1,
                         d[i  , j  ] + (a[i] != b[j]))
    end

    return d[m+1, n+1]
end

function levsort(search, candidates)
    scores = map(cand -> (levenshtein(search, cand), -fuzzyscore(search, cand)), candidates)
    candidates = candidates[sortperm(scores)]
    i = 0
    for i = 1:length(candidates)
        levenshtein(search, candidates[i]) > 3 && break
    end
    return candidates[1:i]
end

# Result printing

function printmatch(io::IO, word, match)
    is, _ = bestmatch(word, match)
    Markdown.with_output_format(:fade, io) do io
        for (i, char) = enumerate(match)
            if i in is
                Markdown.with_output_format(print, :bold, io, char)
            else
                print(io, char)
            end
        end
    end
end

printmatch(args...) = printfuzzy(STDOUT, args...)

function printmatches(io::IO, word, matches; cols = displaysize(io)[2])
    total = 0
    for match in matches
        total + length(match) + 1 > cols && break
        fuzzyscore(word, match) < 0 && break
        print(io, " ")
        printmatch(io, word, match)
        total += length(match) + 1
    end
end

printmatches(args...; cols = displaysize(STDOUT)[2]) = printmatches(STDOUT, args..., cols = cols)

function print_joined_cols(io::IO, ss, delim = "", last = delim; cols = displaysize(io)[2])
    i = 0
    total = 0
    for i = 1:length(ss)
        total += length(ss[i])
        total + max(i-2,0)*length(delim) + (i>1?1:0)*length(last) > cols && (i-=1; break)
    end
    join(io, ss[1:i], delim, last)
end

print_joined_cols(args...; cols = displaysize(STDOUT)[2]) = print_joined_cols(STDOUT, args...; cols=cols)

function print_correction(io, word)
    cors = levsort(word, accessible(current_module()))
    pre = "Perhaps you meant "
    print(io, pre)
    print_joined_cols(io, cors, ", ", " or "; cols = displaysize(io)[2] - length(pre))
    println(io)
    return
end

print_correction(word) = print_correction(STDOUT, word)

# Completion data

const builtins = ["abstract type", "baremodule", "begin", "break",
                  "catch", "ccall", "const", "continue", "do", "else",
                  "elseif", "end", "export", "finally", "for", "function",
                  "global", "if", "import", "importall", "let",
                  "local", "macro", "module", "mutable struct", "primitive type",
                  "quote", "return", "struct", "try", "using", "while"]

moduleusings(mod) = ccall(:jl_module_usings, Any, (Any,), mod)

filtervalid(names) = filter(x->!ismatch(r"#", x), map(string, names))

accessible(mod::Module) =
    [filter!(s->Base.isdeprecated(mod, s), names(mod, true, true));
     map(names, moduleusings(mod))...;
     builtins] |> unique |> filtervalid

completions(name) = fuzzysort(name, accessible(current_module()))
completions(name::Symbol) = completions(string(name))


# Searching and apropos

# Docsearch simply returns true or false if an object contains the given needle
docsearch(haystack::AbstractString, needle) = !isempty(search(haystack, needle))
docsearch(haystack::Symbol, needle) = docsearch(string(haystack), needle)
docsearch(::Void, needle) = false
function docsearch(haystack::Array, needle)
    for elt in haystack
        docsearch(elt, needle) && return true
    end
    false
end
function docsearch(haystack, needle)
    Base.warn_once("unable to search documentation of type $(typeof(haystack))")
    false
end

## Searching specific documentation objects
function docsearch(haystack::MultiDoc, needle)
    for v in values(haystack.docs)
        docsearch(v, needle) && return true
    end
    false
end

function docsearch(haystack::DocStr, needle)
    docsearch(parsedoc(haystack), needle) && return true
    if haskey(haystack.data, :fields)
        for doc in values(haystack.data[:fields])
            docsearch(doc, needle) && return true
        end
    end
    false
end

## Markdown search simply strips all markup and searches plain text version
docsearch(haystack::Markdown.MD, needle) =
    docsearch(stripmd(haystack.content), needle)

"""
    stripmd(x)

Strip all Markdown markup from x, leaving the result in plain text. Used
internally by apropos to make docstrings containing more than one markdown
element searchable.
"""
stripmd(x::ANY) = string(x) # for random objects interpolated into the docstring
stripmd(x::AbstractString) = x  # base case
stripmd(x::Void) = " "
stripmd(x::Vector) = string(map(stripmd, x)...)
stripmd(x::Markdown.BlockQuote) = "$(stripmd(x.content))"
stripmd(x::Markdown.Admonition) = "$(stripmd(x.content))"
stripmd(x::Markdown.Bold) = "$(stripmd(x.text))"
stripmd(x::Markdown.Code) = "$(stripmd(x.code))"
stripmd(x::Markdown.Header) = stripmd(x.text)
stripmd(x::Markdown.HorizontalRule) = " "
stripmd(x::Markdown.Image) = "$(stripmd(x.alt)) $(x.url)"
stripmd(x::Markdown.Italic) = "$(stripmd(x.text))"
stripmd(x::Markdown.LaTeX) = "$(x.formula)"
stripmd(x::Markdown.LineBreak) = " "
stripmd(x::Markdown.Link) = "$(stripmd(x.text)) $(x.url)"
stripmd(x::Markdown.List) = join(map(stripmd, x.items), " ")
stripmd(x::Markdown.MD) = join(map(stripmd, x.content), " ")
stripmd(x::Markdown.Paragraph) = stripmd(x.content)
stripmd(x::Markdown.Footnote) = "$(stripmd(x.id)) $(stripmd(x.text))"
stripmd(x::Markdown.Table) =
    join([join(map(stripmd, r), " ") for r in x.rows], " ")

# Apropos searches through all available documentation for some string or regex
"""
    apropos(string)

Search through all documentation for a string, ignoring case.
"""
apropos(string) = apropos(STDOUT, string)
apropos(io::IO, string) = apropos(io, Regex("\\Q$string", "i"))
function apropos(io::IO, needle::Regex)
    for mod in modules
        # Module doc might be in README.md instead of the META dict
        docsearch(doc(mod), needle) && println(io, mod)
        for (k, v) in meta(mod)
            docsearch(v, needle) && println(io, k)
        end
    end
end