local io = io

local csv = require "csv"
local dir = require "pl.dir"
local lfs = require "lfs"
local uuid = require "uuid"
local path = require "pl.path"
local cksum = require "sha2"

local config = require "config.app"

-- Random number generator for uuid()
local posix_uuid = pcall(function()
    uuid.set_rng(uuid.rng.urandom())
end)
if not posix_uuid then rng = uuid.set_rng(uuid.rng.win_ffi()) end

local M = {}  -- Submission module

-- Adapted from lua-núcleo
local function escape_pattern(s)
    local matches = {
        ["^"] = "%^";
        ["$"] = "%$";
        ["("] = "%(";
        [")"] = "%)";
        ["%"] = "%%";
        ["."] = "%.";
        ["["] = "%[";
        ["]"] = "%]";
        ["*"] = "%*";
        ["+"] = "%+";
        ["-"] = "%-";
        ["?"] = "%?";
        ["\0"] = "%z";
    }

    return (s:gsub(".", matches))
end


M.generate_sip_v1 = function(path)
    --[[
    Version 1 CSV parsing.

    Each row has 3 cells: reference path (ref), metadata key (k), value (v).
    Each v cell contains one value.

    Properties for the same ref can be added in successive rows without
    repeating the ref cell.

    Multiple values can be added in successive rows without repeating the ref
    and v cells.
    --]]

    local sub_data = assert(csv.open(path))
    local md = {}
    local prev_ref, prev_k

    -- Collate metadata.
    local i = 1
    for row in sub_data:lines() do
        ref, k, v = table.unpack(row)
        -- nil-out empty cells (they come through as "")
        if ref == "" then ref = nil end
        if k == "" then k = nil end
        if v == "" then v = nil end

        print("Parsing row:", ref, k, v)
        -- v can be a legit false value.
        if ref and not k and v == nil then
            -- This can be a placeholder for ordering purposes.
            md[ref] = md_ref or {}
            goto continue
        elseif v == nil then
            goto continue
        else
            -- If ref or k are missing, reuse the previous one.
            if ref then prev_ref = ref
            else
                if not prev_ref then
                    -- If column 1 is empty, it must have been set in a
                    -- previous row.
                    error(string.format(
                        "Reference in column 1, row %d not found!", i), 2)
                end
                ref = prev_ref
            end

            if k then prev_k = k
            else
                if not prev_k then
                    -- If column 2 is empty, it must have been set in a
                    -- previous row.
                    error(string.format(
                        "Property key in column 2, row %d not found!", i), 2)
                end
                k = prev_k
            end
        end

        md[ref] = md[ref] or {id = uuid(), path = ref, _sort = i}
        md[ref][k] = md[ref][k] or {}
        if k == "type" then
            md[ref][k] = v
        else
            table.insert(md[ref][k], v)
        end

        ::continue::
        i = i + 1
    end

    -- Move md to an ordered list.
    mdlist = {root_path = path:match("(.*/)")}
    for _, v in pairs(md) do table.insert(mdlist, v) end
    table.sort(mdlist, function (a, b) return (a._sort < b._sort) end)

    -- Infer structure from paths and row ordering.
    for i, v in ipairs(mdlist) do
        for j = i + 1, #mdlist do
            --print(string.format("comparing %s : %s", v.path, mdlist[j].path))
            if not v["next"] and
                    mdlist[j].path:match("(.*/)") == v.path:match("(.*/)") then
                --print("next match.")
                v["next"] = mdlist[j].path
            end
            if not v.firstChild and
                    mdlist[j].path:match("^" .. escape_pattern(v.path)) then
                --print("First child match.")
                v.firstChild = mdlist[j].path
            end
        end
        v._sort = nil
    end

    return mdlist
end


M.generate_sip_v2 = function(path)
    local sub_data = assert(csv.open(path, {header = true}))
    local sip = {root_path = path:match("(.*/)")}

    local prev_path

    local i = 1
    for row in sub_data:lines() do
        print("Processing row: " .. i)
        print("Row path: " .. row["path"])
        if row["path"] ~= "" then
            prev_path = row["path"]
            -- New row.
            sip[i] = {pas_id = uuid()}
            for k, v in pairs(row) do
                if v == "" then goto cont1 end  -- skip empty strings.
                if config.md.single_values[k] then
                    sip[i][k] = v
                else
                    sip[i][k] = {v}
                end
                ::cont1::
            end
            i = i + 1
        else
            -- Continuation of values from a previous row.
            if i == 1 then
                error("First row MUST have a path value.", 2)
            elseif not prev_path then
                error(("No path information at row %d"):format(i), 2)
            else
                row.path = prev_path
                for k, v in pairs(row) do
                    if v == "" then goto cont2 end  -- skip empty strings.
                    if config.md.single_values[k] then
                        -- It doesn't make much sense to overwrite, maybe throw an error?
                        sip[i - 1][k] = v
                    else
                        print("Value: " .. v)
                        print("Inserting at row " .. i -1)
                        table.insert(sip[i - 1][k], v)
                    end
                    ::cont2::
                end
            end
        end
    end

    return sip
end


M.validate = function(sip)
    -- TODO
end

M.deposit = function(sip)
    for i, rsrc in ipairs(sip) do
        print(("Processing resource #%d of %d: %s"):format(i, #sip, rsrc.id))

        in_path = sip.root_path .. rsrc.path
        -- If it's a directory, skip processing.
        if not path.isfile(in_path) then goto continue end

        local tmp_dir = config.fs.ores_path .. "tmp/"
        local tmp_path = tmp_dir .. rsrc.id
        dir.makepath(tmp_dir)

        local ifh = io.open(in_path, "r")
        local ofh = io.open(tmp_path, "w")

        b2 = cksum.blake2b()
        while true do
            chunk = ifh:read(config.fs.stream_chunk_size)
            if not chunk then break end
            b2(chunk)
            ofh:write(chunk)
        end
        rsrc.b2checksum = b2()

        ofh:close()
        ifh:close()

        out_dir = ("%s%s/%s/"):format(
                config.fs.ores_path,
                rsrc.b2checksum:sub(1,4),
                rsrc.b2checksum:sub(5,8))
        out_path = out_dir .. rsrc.b2checksum
        rsrc.path = out_path
        dir.makepath(out_dir)
        print(("Moving file %s"):format(rsrc.id))
        dir.movefile(tmp_path, rsrc.path)

        ::continue::
    end
end

return M