require 'lpeg'

local Q            = lpeg.P('"')
local quoted_value = Q * lpeg.Cs( ((1 - Q) + Q*Q / '"')^0 ) * Q
local raw_value    = lpeg.C( (1 - lpeg.S(',\r\n"'))^0 )
local field        = (lpeg.P(' ')^0 * quoted_value * lpeg.P(' ')^0 + raw_value) * lpeg.Cp()

local cr, lf = string.byte("\r\n", 1, 2)
local space = string.byte(" ", 1)

-- Loads the data from a CSV file into the 'data' table
-- 'fields_remap' maps indexes to column key names
-- 'skip_rows' causes the first (or more) rows to be skipped
---
--- Loads the data from a CSV file into the 'data' table.
---
--- @param filename string The path to the CSV file to load.
--- @param data table The table to store the loaded CSV data.
--- @param fields_remap table A mapping of column indices to column key names.
--- @param skip_rows number The number of rows to skip at the beginning of the file.
--- @return table The 'data' table containing the loaded CSV data.
---
function LoadCSV(filename, data, fields_remap, skip_rows)
    local err, str = AsyncFileToString(filename)
    if err or not str then
        return
    end

    skip_rows = type(skip_rows) == "number" and skip_rows or skip_rows and 1 or 0
    data = data or {}
    local pos, col, row = 1, 1, {}
    local value

    while true do
        value, pos = field:match(str, pos)
        -- If there is are trailing spaces, remove all exept one
        local n = #value
        while n > 0 and value:byte(n) == space do
            n = n - 1
        end
        if #value - n > 1 then
            value = value:sub(1, n + 1)
        end

        if not fields_remap then
            row[col] = value
        elseif fields_remap[col] then
            row[fields_remap[col]] = value
        end

        local ch = str:byte(pos)
        if ch == lf or ch == cr or pos >= #str then
            if skip_rows > 0 then
                skip_rows = skip_rows - 1
            else
                data[#data + 1] = row
            end

            ch = (ch or 0) + (str:byte(pos + 1) or 0)
            pos = pos + (ch == cr + lf and 2 or 1)
            if pos >= #str then
                break
            end
            col = 1
            row = {}
        else
            col = col + 1
            pos = pos + 1
        end
    end
    return data
end

-- Saves the table data in a CSV file
-- if the row tables data[1], etc. have non-numeric indices, 
-- 'fields_remap' specifies the field name for each index
---
--- Saves the contents of a table in a CSV file.
---
--- @param filename string The path to the CSV file to save.
--- @param data table The table of data to save.
--- @param fields_remap table (optional) A table that maps the indices of the data table to the field names.
--- @param captions table (optional) A table of field names to use as the header row.
--- @param separator string (optional) The character to use as the field separator.
--- @return boolean True if the file was saved successfully, false otherwise.
function SaveCSV(filename, data, fields_remap, captions, separator)
    local pstr_f = pstr("", 1024 * 1024)
    if separator then
        pstr_f:append('sep=', separator, '\n')
    else
        separator = ','
    end

    local function append_row_values(row, fields)
        for i = 1, fields and #fields or #row do
            local value = row[not fields and i or fields[i]]
            if IsT(value) then
                value = TDevModeGetEnglishText(value, false, true)
            end
            value = (not value) and "" or tostring(value)
            if value:find('[,\t\r\n"]') then
                value = '"' .. value:gsub('"', '""') .. '"'
            end
            if i > 1 then
                pstr_f:append(separator)
            end
            pstr_f:append(value)
        end
        pstr_f:append('\n')
    end

    if captions then
        append_row_values(captions)
    end

    for _, row in ipairs(data) do
        append_row_values(row, fields_remap)
    end

    return AsyncStringToFile(filename, pstr_f)
end

-- Saves the table data in a TXT file
-- if the row tables data[1], etc. have non-numeric indices, 
-- 'fields_incl' specifies the which fields to be included 
---
--- Saves the contents of a table in a TXT file.
---
--- @param filename string The path to the TXT file to save.
--- @param data table The table of data to save.
--- @param fields_incl table (optional) A table of field indices to include in the output.
--- @param captions table (optional) A table of field names to use as the header row.
--- @return boolean True if the file was saved successfully, false otherwise.
function SaveIDDiffFile(filename, data, fields_incl, captions)
    local f = io.open(filename, "w+")

    for i = (captions and 0 or 1), #data do
        local row = (i == 0 and captions or data[i])

        local values, n = {}, fields_incl and #fields_incl
        for j = 1, n do
            local value = fields_incl and i ~= 0 and row[fields_incl[j]] or row[j]
            value = (value == nil) and "" or tostring(value)
            table.insert(values, value)
        end
        f:write(table.concat(values, "\t"))
        f:write("\n")
    end

    f:close()
end