local io = io

local csv = require "csv"
local dir = require "pl.dir"
local libmagic = require "libmagic"
local plpath = require "pl.path"
local pp = require "pl.pretty"

local term = require "volksdata.term"
local triple = require "volksdata.triple"
local graph = require "volksdata.graph"

local pkar = require "pocket_archive"
local model = require "pocket_archive.model"
local mc = require "pocket_archive.monocypher"
local transformers = require "pocket_archive.transformers"
local validator = require "pocket_archive.validator"

local logger = pkar.logger
local dbg = require "debugger"

-- "nil" table - for missing key fallback in chaining.
local NT = {}

local M = {}  -- Submission module

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

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


--[[
    Only generate a thumbnail for pas:File types.

    Non-file resources may be assigned a thumbnail from a contained file
    or from a stock type icon in the metadata population phase.
--]]
--[=[
local function generate_thumbnail(rsrc, sip_root, tn_dir)
    local mconf = model.models[rsrc["pas:contentType"]]
    if not mconf.types["pas:File"] then return end

    local txconf = (mconf.transformers or NT).thumbnail or {fn = "type_icon"}
    local src = plpath.join(sip_root, rsrc["pas:sourcePath"])
    local dest_fname = rsrc.id:gsub("^par:", "")
    local ext = txconf.ext or plpath.extension(src)
    local dest = plpath.join(tn_dir, dest_fname .. ext)
    assert(transformers[txconf.fn](
            src, dest, table.unpack(txconf or NT)))
    local deliverable = dest:gsub(pkar.config.htmlgen.out_dir, "..")
    logger:debug("thumbnail: ", dest)

    return dest
end
--]=]


-- Initialize libmagic database.
local magic = libmagic.open( libmagic.MIME_TYPE, libmagic.NO_CHECK_COMPRESS )
assert(magic:load())


-- For idgen(). Makes a 60-character pool with ~5.9 bits of entropy per char.
local chpool = {}
for i = 48, 57  do table.insert(chpool, i) end  -- 0-9
for i = 65, 90  do table.insert(chpool, i) end  -- A-Z
for i = 97, 122 do table.insert(chpool, i) end  -- a-z

--[[
Generate a random, reader-friendly ID.

A 16-character ID with the above defined #chpool of 60 smybols has an entropy
of 94.5 bits, which should be plenty for a small repository.
]]
M.idgen = function(len)
    local charlist = {}
    for i = 1, (len or pkar.config.id.len) do
        table.insert(charlist, string.char(chpool[math.random(1, #chpool)]))
    end

    return table.concat(charlist)
end


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

    local tn_dir = plpath.join(sip.root_path, "proc", "tn")
    dir.makepath(tn_dir)

    local prev_path

    local i = 0
    local row_n = 2  -- Skipping header row.
    for row in sub_data:lines() do
        logger:debug("Row path: ", row["pas:sourcePath"])
        logger:debug("Parsing row:", pp.write(row))
        if row["pas:sourcePath"] ~= "" then
            i = i + 1
            logger:info(
                    ("Processing LL resource #%d at row #%d.")
                    :format(i, row_n))
            prev_path = row["pas:sourcePath"]
            -- New row.
            local id
            if row.id then
                id = "par:" .. row.id
                row.id = nil
            else id = "par:" .. M.idgen() end
            sip[i] = {id = id}
            for k, v in pairs(row) do
                if v == "" then goto cont1 end  -- skip empty strings.
                if pkar.config.md.single_values[k] then sip[i][k] = v
                else sip[i][k] = {[v] = true} end  -- Multi-values are a set.
                ::cont1::
            end

            --[[
            -- Generate thumbnail for files.
            local rsrc_path = plpath.join(
                    sip.root_path, sip[i]["pas:sourcePath"])
            if plpath.isfile(rsrc_path) then
                --require "debugger"()
                sip[i]["pas:thumbnail"] = generate_thumbnail(
                        sip[i], sip.root_path, tn_dir)
            end
            --]]
        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
                for k, v in pairs(row) do
                    if v == "" then goto cont2 end  -- skip empty strings.
                    if pkar.config.md.single_values[k] then
                        -- It doesn't make much sense to overwrite, maybe throw an error?
                        error(
                            ("On CSV row #%d: field %s is single-valued.")
                            :format(row_n, k))
                    else
                        logger:debug("Value: ", v)
                        logger:debug("Inserting at row ", i - 1)
                        sip[i][k][v] = true
                    end
                    ::cont2::
                end
                row["pas:sourcePath"] = prev_path
            end
        end
        row_n = row_n + 1
    end
    -- Infer structure from paths and row ordering.
    for i, v in ipairs(sip) do
        local rmod = model.parse_model(v["pas:contentType"])
        if rmod.properties["pas:next"] then
            for j = i + 1, #sip do
                if not v["pas:next"] and
                        sip[j]["pas:sourcePath"]:match("(.*/)") ==
                                v["pas:sourcePath"]:match("(.*/)") then
                    v["pas:next"] = sip[j].id
                end
            end
        end
        if rmod.properties["pas:first"] then
            for j = i + 1, #sip do
                if not v["pas:first"] and
                    sip[j]["pas:sourcePath"]:match(
                            "^" .. escape_pattern(v["pas:sourcePath"])
                ) then
                    v["pas:first"] = sip[j].id
                end
            end
        end
    end
    --require "debugger"()

    return sip
end


--[[  Convert a SIP resource table to an in-memory Volksdata graph.

--]]
M.rsrc_to_graph = function(rsrc)
    local rmod = model.parse_model(rsrc["pas:contentType"])
    logger:info("Updating resource md: ", pp.write(rsrc))

    local s = term.new_iriref_ns(rsrc.id)
    triples = {}

    for k, v in pairs(rsrc) do
        -- id is the subject, it won't be an attribute.
        if k == "id" then goto skip end

        logger:debug(("Adding attribute: %s = %s"):format(k, pp.write(v)))
        local p = term.new_iriref_ns(k)
        local o
        local datatype = ((rmod.properties or NT)[k] or NT).type
        local rdf_type_str = pkar.config.md.datatypes[datatype]
        local rdf_type
        if rdf_type_str then
            rdf_type = term.new_iriref_ns(rdf_type_str).data
        end
        -- Force all fields to be multi-valued.
        if type(v) ~= "table" then v = {[v] = true} end
        for vv in pairs(v) do
            if k == "pas:contentType" then
                vv = "pas:" .. vv
            end
            if datatype == "resource" then
                o = term.new_iriref_ns(vv)
            elseif datatype == "ext_resource" then
                o = term.new_iriref(vv)
            else o = term.new_lit(vv, rdf_type) end
            table.insert(triples, triple.new(s, p, o))
        end
        ::skip::
    end
    for i, m in ipairs(rmod.lineage) do
        table.insert(
            triples, triple.new(s, pkar.RDF_TYPE, term.new_iriref_ns(m)))
    end

    local gr = graph.new(nil)
    -- This is a full replacement.
    --require "debugger"()
    logger:info("Removing triples.")
    gr:remove(s)
    logger:info("Adding triples.")
    -- TODO implement volksdata_lua fn to add a single triple and add triples
    -- in the previous loop.
    gr:add(triples)

    return gr, s
end


M.store_updates = function(tmp_gr, s)
    -- TODO use a transaction when volksdata_lua supports it.
    logger:debug("Graph: ", tmp_gr:encode("ttl"))

    local val_report = validator.validate(tmp_gr, s)
    if val_report.max_level == "ERROR" then error(
        "Validation raised errors: " .. pp.write(val_report))
    elseif val_report.max_level == "WARN" then logger:warn(
        "Validation raised warnings: " .. pp.write(val_report))
    elseif val_report.max_level == "NOTICE" then logger:warn(
        "Validation raised notices: " .. pp.write(val_report)) end

    local stored_gr = graph.new(pkar.store, term.DEFAULT_CTX)

    return tmp_gr:copy(stored_gr)
end


M.deposit = function(sip)
    for i, rsrc in ipairs(sip) do
        -- TODO Wrap this chunk into a txn. Each row is atomic.
        logger:debug(("Processing resource #%d of %d: %s"):format(
                i, #sip, rsrc.id))

        local in_path = sip.root_path .. rsrc["pas:sourcePath"]
        local fext = plpath.extension(in_path)
        -- If it's a directory, skip file processing.
        if not plpath.isfile(in_path) then goto continue end

        do
            local tmp_dir = plpath.join(pkar.config.fs.ores_path, "tmp/")
            local file_ext
            _, file_ext = plpath.splitext(in_path)
            local tmp_path = tmp_dir .. rsrc.id .. file_ext
            dir.makepath(tmp_dir)

            local ifh = assert(io.open(in_path, "r"))

            rsrc["dc:format"] = {[magic:filehandle(ifh)] = true}
            local hash_it = mc.new_blake2b()
            local fsize = 0
            logger:debug("Hashing ", in_path)
            local ofh = assert(io.open(tmp_path, "w"))
            while true do
                chunk = ifh:read(pkar.config.fs.stream_chunk_size)
                if not chunk then break end
                hash_it:update(chunk)
                ofh:write(chunk)
                fsize = fsize + #chunk
            end
            local checksum = hash_it:final(true)
            rsrc["premis:hasMessageDigest"] = {
                    ["urn:blake2:" .. checksum] = true}
            rsrc["dc:extent"] = fsize

            ofh:close()
            ifh:close()

            -- Copy file and calculate checksum.
            local out_dir, out_path
            out_dir = plpath.join(
                    pkar.config.fs.ores_path,
                    checksum:sub(1, 2),
                    checksum:sub(3, 4))
            out_path = plpath.join(out_dir, checksum:sub(1,32) .. fext)
            dir.makepath(out_dir)
            logger:debug(("Moving file %s to %s"):format(tmp_path, out_path))
            dir.movefile(tmp_path, out_path)
            rsrc["pas:path"] = out_path

            -- Copy thumbnail if existing.
            if rsrc["pas:thumbnail"] then
                src_path = rsrc["pas:thumbnail"] 
                out_path = plpath.join(
                        out_dir, plpath.basename(src_path))
                logger:debug(("Moving file %s to %s"):format(src_path, out_path))
                dir.movefile(src_path, out_path)
                rsrc["pas:thumbnail"] = out_path
            end
        end

        ::continue::

        tstamp = os.date("!%Y-%m-%dT%TZ")
        rsrc["dc:created"] = tstamp
        rsrc["dc:modified"] = tstamp
        M.store_updates(M.rsrc_to_graph(rsrc))
    end

    -- Remove processing directory.
    dir.rmtree(plpath.join(sip.root_path, "proc"))
end


return M