local ckind      = require 'define.CompletionItemKind'
local files      = require 'files'
local guide      = require 'parser.guide'
local matchKey   = require 'core.matchKey'
local vm         = require 'vm'
local library    = require 'library'
local getLabel   = require 'core.hover.label'
local getName    = require 'core.hover.name'
local getArg     = require 'core.hover.arg'
local getDesc    = require 'core.hover.description'
local getHover   = require 'core.hover'
local config     = require 'config'
local util       = require 'utility'
local markdown   = require 'provider.markdown'
local findSource = require 'core.find-source'

local stackID = 0
local stacks = {}
local function stack(callback)
    stackID = stackID + 1
    stacks[stackID] = callback
    return stackID
end

local function clearStack()
    stacks = {}
end

local function resolveStack(id)
    local callback = stacks[id]
    if not callback then
        return nil
    end
    return callback()
end

local function isSpace(char)
    if char == ' '
    or char == '\n'
    or char == '\r'
    or char == '\t' then
        return true
    end
    return false
end

local function skipSpace(text, offset)
    for i = offset, 1, -1 do
        local char = text:sub(i, i)
        if not isSpace(char) then
            return i
        end
    end
    return 0
end

local function findWord(text, offset)
    for i = offset, 1, -1 do
        if not text:sub(i, i):match '[%w_]' then
            if i == offset then
                return nil
            end
            return text:sub(i+1, offset), i+1
        end
    end
    return text:sub(1, offset), 1
end

local function findSymbol(text, offset)
    for i = offset, 1, -1 do
        local char = text:sub(i, i)
        if isSpace(char) then
            goto CONTINUE
        end
        if char == '.'
        or char == ':'
        or char == '#' then
            return char, i
        else
            return nil
        end
        ::CONTINUE::
    end
    return nil
end

local function findAnyPos(text, offset)
    for i = offset, 1, -1 do
        if not isSpace(text:sub(i, i)) then
            return i
        end
    end
    return nil
end

local function findParent(ast, text, offset)
    for i = offset, 1, -1 do
        local char = text:sub(i, i)
        if isSpace(char) then
            goto CONTINUE
        end
        local oop
        if char == '.' then
            oop = false
        elseif char == ':' then
            oop = true
        else
            return nil, nil
        end
        local anyPos = findAnyPos(text, i-1)
        if not anyPos then
            return nil, nil
        end
        local parent = guide.eachSourceContain(ast.ast, anyPos, function (source)
            if source.finish == anyPos then
                return source
            end
        end)
        if parent then
            return parent, oop
        end
        ::CONTINUE::
    end
    return nil, nil
end

local function buildFunctionSnip(source)
    local name = getName(source):gsub('^.-[$.:]', '')
    local args = vm.eachDef(source, function (src)
        if src.type == 'function' then
            local args = getArg(src)
            if args ~= '' then
                return args
            end
        end
    end) or ''
    local id = 0
    args = args:gsub('[^,]+', function (arg)
        id = id + 1
        return arg:gsub('^(%s*)(.+)', function (sp, word)
            return ('%s${%d:%s}'):format(sp, id, word)
        end)
    end)
    return ('%s(%s)'):format(name, args)
end

local function buildDetail(source)
    local types = vm.getType(source)
    return types
end

local function buildDesc(source)
    local hover = getHover.get(source)
    local md = markdown()
    md:add('lua', hover.label)
    md:add('md',  hover.description)
    return md:string()
end

local function buildFunction(results, source, oop, data)
    local snipType = config.config.completion.callSnippet
    if snipType == 'Disable' or snipType == 'Both' then
        results[#results+1] = data
    end
    if snipType == 'Both' or snipType == 'Replace' then
        local snipData = util.deepCopy(data)
        snipData.kind = ckind.Snippet
        snipData.label = snipData.label .. '()'
        snipData.insertText = buildFunctionSnip(source)
        snipData.insertTextFormat = 2
        snipData.id  = stack(function ()
            return {
                detail      = buildDetail(source),
                description = buildDesc(source),
            }
        end)
        results[#results+1] = snipData
    end
end

local function isSameSource(source, pos)
    return source.start <= pos and source.finish >= pos
end

local function checkLocal(ast, word, offset, results)
    local locals = guide.getVisibleLocals(ast.ast, offset)
    for name, source in pairs(locals) do
        if isSameSource(source, offset) then
            goto CONTINUE
        end
        if not matchKey(word, name) then
            goto CONTINUE
        end
        if vm.hasType(source, 'function') then
            buildFunction(results, source, false, {
                label  = name,
                kind   = ckind.Function,
                id     = stack(function ()
                    return {
                        detail      = buildDetail(source),
                        description = buildDesc(source),
                    }
                end),
            })
        else
            results[#results+1] = {
                label  = name,
                kind   = ckind.Variable,
                id     = stack(function ()
                    return {
                        detail      = buildDetail(source),
                        description = buildDesc(source),
                    }
                end),
            }
        end
        ::CONTINUE::
    end
end

local function checkFieldThen(src, used, word, start, parent, oop, results)
    local key = vm.getKeyName(src)
    if not key or key:sub(1, 1) ~= 's' then
        return
    end
    if isSameSource(src, start) then
        return
    end
    local name = key:sub(3)
    if used[name] then
        return
    end
    if not matchKey(word, name) then
        used[name] = true
        return
    end
    local kind = ckind.Field
    if vm.hasType(src, 'function') then
        if oop then
            kind = ckind.Method
        else
            kind = ckind.Function
        end
        used[name] = true
        buildFunction(results, src, oop, {
            label = name,
            kind  = kind,
            id    = stack(function ()
                return {
                    detail      = buildDetail(src),
                    description = buildDesc(src),
                }
            end),
        })
    else
        if oop then
            return
        end
        used[name] = true
        local literal = vm.getLiteral(src)
        if literal ~= nil then
            kind = ckind.Enum
        end
        results[#results+1] = {
            label = name,
            kind  = kind,
            id    = stack(function ()
                return {
                    detail      = buildDetail(src),
                    description = buildDesc(src),
                }
            end)
        }
    end
end

local function checkField(word, start, parent, oop, results)
    local used = {}
    if parent.ref then
        for _, src in ipairs(parent.ref) do
            checkFieldThen(src, used, word, start, parent, oop, results)
        end
    end
    vm.eachField(parent, function (src)
        checkFieldThen(src, used, word, start, parent, oop, results)
    end)
    return used
end

local function checkTableField(ast, word, start, results)
    local source = guide.eachSourceContain(ast.ast, start, function (source)
        if  source.start == start
        and source.parent
        and source.parent.type == 'table' then
            return source
        end
    end)
    if not source then
        return
    end
    local used = {}
    guide.eachSourceType(ast.ast, 'tablefield', function (src)
        if not src.field then
            return
        end
        local key = src.field[1]
        if  not used[key]
        and matchKey(word, key)
        and src ~= source then
            used[key] = true
            results[#results+1] = {
                label = key,
                kind  = ckind.Property,
            }
        end
    end)
end

local function checkCommon(word, text, results)
    local used = {}
    for _, result in ipairs(results) do
        used[result.label] = true
    end
    for str in text:gmatch '[%a_][%w_]*' do
        if not used[str] and str ~= word then
            used[str] = true
            if matchKey(word, str) then
                results[#results+1] = {
                    label = str,
                    kind  = ckind.Text,
                }
            end
        end
    end
end

local function isInString(ast, offset)
    return guide.eachSourceContain(ast.ast, offset, function (source)
        if source.type == 'string' then
            return true
        end
    end)
end

local keyWordMap = {
{'do', function (hasSpace, results)
    if hasSpace then
        results[#results+1] = {
            label = 'do .. end',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[$0 end]],
        }
    else
        results[#results+1] = {
            label = 'do .. end',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
do
    $0
end]],
        }
    end
    return true
end, function (ast, start)
    return guide.eachSourceContain(ast.ast, start, function (source)
        if source.type == 'while'
        or source.type == 'in'
        or source.type == 'loop' then
            for i = 1, #source.keyword do
                if start == source.keyword[i] then
                    return true
                end
            end
        end
    end)
end},
{'and'},
{'break'},
{'else'},
{'elseif', function (hasSpace, results)
    if hasSpace then
        results[#results+1] = {
            label = 'elseif .. then',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[$1 then]],
        }
    else
        results[#results+1] = {
            label = 'elseif .. then',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[elseif $1 then]],
        }
    end
    return true
end},
{'end'},
{'false'},
{'for', function (hasSpace, results)
    if hasSpace then
        results[#results+1] = {
            label = 'for .. in',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
${1:key, value} in ${2:pairs(${3:t})} do
    $0
end]]
        }
        results[#results+1] = {
            label = 'for i = ..',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
${1:i} = ${2:1}, ${3:10, 1} do
    $0
end]]
        }
    else
        results[#results+1] = {
            label = 'for .. in',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
for ${1:key, value} in ${2:pairs(${3:t})} do
    $0
end]]
        }
        results[#results+1] = {
            label = 'for i = ..',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
for ${1:i} = ${2:1}, ${3:10, 1} do
    $0
end]]
        }
    end
    return true
end},
{'function', function (hasSpace, results)
    if hasSpace then
        results[#results+1] = {
            label = 'function ()',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
$1($2)
    $0
end]]
        }
    else
        results[#results+1] = {
            label = 'function ()',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
function $1($2)
    $0
end]]
        }
    end
    return true
end},
{'goto'},
{'if', function (hasSpace, results)
    if hasSpace then
        results[#results+1] = {
            label = 'if .. then',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
$1 then
    $0
end]]
        }
    else
        results[#results+1] = {
            label = 'if .. then',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
if $1 then
    $0
end]]
        }
    end
    return true
end},
{'in', function (hasSpace, results)
    if hasSpace then
        results[#results+1] = {
            label = 'in ..',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
${1:pairs(${2:t})} do
    $0
end]]
        }
    else
        results[#results+1] = {
            label = 'in ..',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
in ${1:pairs(${2:t})} do
    $0
end]]
        }
    end
    return true
end},
{'local', function (hasSpace, results)
    if hasSpace then
        results[#results+1] = {
            label = 'local function',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
function $1($2)
    $0
end]]
        }
    else
        results[#results+1] = {
            label = 'local function',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
local function $1($2)
    $0
end]]
        }
    end
    return false
end},
{'nil'},
{'not'},
{'or'},
{'repeat', function (hasSpace, results)
    if hasSpace then
        results[#results+1] = {
            label = 'repeat .. until',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[$0 until $1]]
        }
    else
        results[#results+1] = {
            label = 'repeat .. until',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
repeat
    $0
until $1]]
        }
    end
    return true
end},
{'return', function (hasSpace, results)
    if not hasSpace then
        results[#results+1] = {
            label = 'do return end',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[do return $1end]]
        }
    end
    return false
end},
{'then'},
{'true'},
{'until'},
{'while', function (hasSpace, results)
    if hasSpace then
        results[#results+1] = {
            label = 'while .. do',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
${1:true} do
    $0
end]]
        }
    else
        results[#results+1] = {
            label = 'while .. do',
            kind  = ckind.Snippet,
            insertTextFormat = 2,
            insertText = [[
while ${1:true} do
    $0
end]]
        }
    end
    return true
end},
}

local function checkKeyWord(ast, text, start, word, hasSpace, afterLocal, results)
    local snipType = config.config.completion.keywordSnippet
    for _, data in ipairs(keyWordMap) do
        local key = data[1]
        local eq
        if hasSpace then
            eq = word == key
        else
            eq = matchKey(word, key)
        end
        if afterLocal and key ~= 'function' then
            eq = false
        end
        if eq then
            local replaced
            local extra
            if snipType == 'Both' or snipType == 'Replace' then
                local func = data[2]
                if func then
                    replaced = func(hasSpace, results)
                    extra = true
                end
            end
            if snipType == 'Both' then
                replaced = false
            end
            if not replaced then
                if not hasSpace then
                    local item = {
                        label = key,
                        kind  = ckind.Keyword,
                    }
                    if extra then
                        table.insert(results, #results, item)
                    else
                        results[#results+1] = item
                    end
                end
            end
            local checkStop = data[3]
            if checkStop then
                local stop = checkStop(ast, start)
                if stop then
                    return true
                end
            end
        end
    end
end

local function checkProvideLocal(ast, word, start, results)
    local block
    guide.eachSourceContain(ast.ast, start, function (source)
        if source.type == 'function'
        or source.type == 'main' then
            block = source
        end
    end)
    if not block then
        return
    end
    guide.eachSourceType(block, 'getglobal', function (source)
        if source.start > start
        and matchKey(word, source[1]) then
            results[#results+1] = {
                label = source[1],
                kind  = ckind.Variable,
            }
        end
    end)
end

local function isAfterLocal(text, start)
    local pos = skipSpace(text, start-1)
    local word = findWord(text, pos)
    return word == 'local'
end

local function tryWord(ast, text, offset, results)
    local finish = skipSpace(text, offset)
    local word, start = findWord(text, finish)
    if not word then
        return nil
    end
    local hasSpace = finish ~= offset
    if not isInString(ast, offset) then
        local parent, oop = findParent(ast, text, start - 1)
        if parent then
            if not hasSpace then
                checkField(word, start, parent, oop, results)
            end
        else
            local afterLocal = isAfterLocal(text, start)
            local stop = checkKeyWord(ast, text, start, word, hasSpace, afterLocal, results)
            if stop then
                return
            end
            if not hasSpace then
                if afterLocal then
                    checkProvideLocal(ast, word, start, results)
                else
                    checkLocal(ast, word, start, results)
                    checkTableField(ast, word, start, results)
                    local env = guide.getLocal(ast.ast, '_ENV', start)
                    checkField(word, start, env, false, results)
                end
            end
        end
    end
    if not hasSpace then
        checkCommon(word, text, results)
    end
end

local function trySymbol(ast, text, offset, results)
    local symbol, start = findSymbol(text, offset)
    if not symbol then
        return nil
    end
    if isInString(ast, offset) then
        return nil
    end
    if symbol == '.'
    or symbol == ':' then
        local parent, oop = findParent(ast, text, start)
        if parent then
            checkField('', start, parent, oop, results)
        end
    end
end

local function completion(uri, offset)
    local ast = files.getAst(uri)
    local text = files.getText(uri)
    local results = {}
    clearStack()
    if ast then
        tryWord(ast, text, offset, results)
        trySymbol(ast, text, offset, results)
    else
        local word = findWord(text, offset)
        if word then
            checkCommon(word, text, results)
        end
    end

    if #results == 0 then
        return nil
    end
    return results
end

local function resolve(id)
    return resolveStack(id)
end

return {
    completion = completion,
    resolve    = resolve,
}