-- Quick and dirty meta data store. Ineffcient and
-- not safe with concurrent access.
-- This should only be used for non-public single-user
-- test setups.
-- WARNING: this module has never even been tested. It is just here
-- to give an example of MetaDataStore implementation.
module FileMetaDataStore where

import ImageInfo
import MetaDataStore

import Data.List

fileMetaDataStore :: FilePath -> MetaDataStore
fileMetaDataStore file = MetaDataStore {
   addImageInfo = file_addImageInfo file,
   getAllImages = file_getAllImages file,
   getImageByID = file_getImageByID file,
   getImagesByTag = file_getImagesByTag file,
   getAllTags = file_getAllTags file,
   addTag = file_addTag file,
   removeTag = file_removeTag file,
   setProperty = file_setProperty file
 }

file_addImageInfo file info = 
    do
    appendFile file (show info)

file_getAllImages file = 
    do
    s <- readFile file
    return $ map read $ lines s

file_getImageByID file id = 
    do
    is <- file_getAllImages file
    return $ head [ i | i <- is, key i == id]

file_getImagesByTag file tag = 
    do
    is <- file_getAllImages file
    return [ i | i <- is, tag `elem` tags i]

file_getAllTags file = 
    do
    is <- file_getAllImages file
    return $ foldr union [] $ map tags is

update file info =
    do
    is <- file_getAllImages file
    let is' = [ if key i == key info then info else i | i <- is ]
    writeFile file $ unlines $ map show is'
    return info

file_addTag file info tag = 
    update file (info {tags = tags info `union` [tag] })

file_removeTag file info tag = 
    update file (info {tags = delete tag (tags info) })

file_setProperty file info prop = 
    update file (info {properties = setProp prop (properties info) })

setProp (k,v) ps =
    [ if k' == k then (k,v) else p | p@(k',_) <- ps ]