From 2dd980b92c4ee0c4a16c2899a55ecfffc5ee5d6d Mon Sep 17 00:00:00 2001
From: Alex Ling <hkalexling@gmail.com>
Date: Wed, 26 Feb 2020 17:41:50 +0000
Subject: [PATCH] Add mangadex/downloader.cr (implements MangaDex::Job and
 MangaDex::Queue)

---
 src/mangadex/downloader.cr | 144 +++++++++++++++++++++++++++++++++++++
 1 file changed, 144 insertions(+)
 create mode 100644 src/mangadex/downloader.cr

diff --git a/src/mangadex/downloader.cr b/src/mangadex/downloader.cr
new file mode 100644
index 0000000..568b990
--- /dev/null
+++ b/src/mangadex/downloader.cr
@@ -0,0 +1,144 @@
+require "./api"
+require "sqlite3"
+
+module MangaDex
+	enum JobStatus
+		Pending     # 0
+		Downloading # 1
+		Error       # 2
+		Completed   # 3
+	end
+	struct Job
+		property id : String
+		property manga_id : String
+		property title : String
+		property manga_title : String
+		property status : JobStatus
+		property log : String
+		property time : Time
+		private def load_query_result(res : DB::ResultSet)
+			begin
+				@id, @manga_id, @title, @manga_title, status, @log, time = \
+					res.as {String, String, String, String, Int32, String, Int64}
+				@status = JobStatus.new status
+				@time = Time.unix time
+				return true
+			rescue e
+				puts e
+				return false
+			end
+		end
+		def self.from_query_result(res : DB::ResultSet)
+			job = Job.allocate
+			success = job.load_query_result res
+			return success ? job : nil
+		end
+		def initialize(@id, @manga_id, @title, @manga_title, @status, @log,
+					   @time)
+		end
+	end
+	class Queue
+		def initialize(@path : String)
+			dir = File.dirname path
+			unless Dir.exists? dir
+				puts "The queue DB directory #{dir} does not exist. " \
+					"Attepmting to create it"
+				Dir.mkdir_p dir
+			end
+			DB.open "sqlite3://#{@path}" do |db|
+				begin
+					db.exec "create table queue" \
+						"(id string, manga_id string, title text," \
+						"manga_title text, status integer, log text, time integer)"
+					db.exec "create unique index id_idx on queue (id)"
+					db.exec "create index manga_id_idx on queue (manga_id)"
+					db.exec "create index status_idx on queue (status)"
+				rescue e
+					unless e.message == "table queue already exists"
+						puts "Error when checking tables in DB: #{e}"
+						raise e
+					end
+				end
+			end
+		end
+		# Returns the earliest job in queue or nil if the job cannot be parsed.
+		#	Raises DB::Error if queue is empty
+		def pop
+			DB.open "sqlite3://#{@path}" do |db|
+				res = db.query_one "select * from queue where status = 0 "\
+					"order by time limit 1"
+				job = Job.from_query_result res
+				db.exec "delete from queue where id = (select id from queue "\
+					"where status = 0 order by time limit 1)"
+				return job
+			end
+		end
+		def push(job)
+			begin
+				DB.open "sqlite3://#{@path}" do |db|
+					db.exec "insert into queue values (?, ?, ?, ?, ?, ?, ?)",
+						job.id, job.manga_id, job.title, job.manga_title,
+						job.status.to_i, job.log, job.time.to_unix
+				end
+				return true
+			rescue
+				return false
+			end
+		end
+		# Push an array of jobs into the queue, and return the number of jobs
+		#	inserted. Any job already exists in the queue will be ignored.
+		def push(jobs : Array(Job))
+			start_count = self.count
+			DB.open "sqlite3://#{@path}" do |db|
+				jobs.each {|job|
+					db.exec "insert or ignore into queue values "\
+						"(?, ?, ?, ?, ?, ?, ?)",
+						job.id, job.manga_id, job.title, job.manga_title,
+						job.status.to_i, job.log, job.time.to_unix
+				}
+			end
+			self.count - start_count
+		end
+		#def push(job)
+			#sucess = false
+			#DB.open "sqlite3://#{@path}" do |db|
+				#trans = db.begin_transaction
+				#con = trans.connection
+				#begin
+					#con.exec "insert into queue values (?, ?, ?, ?, ?, ?, ?)",
+						#job.id, job.manga_id, job.title, job.manga_title,
+						#job.status.to_i, job.log, job.time.to_unix
+				#rescue
+					#trans.rollback
+				#else
+					#trans.commit
+					#success = true
+				#end
+				#con.close
+				#trans.close
+			#end
+			#success
+		#end
+		def delete(id)
+			DB.open "sqlite3://#{@path}" do |db|
+				db.exec "delete from queue where id = (?)", id
+			end
+		end
+		def delete_status(status : JobStatus)
+			DB.open "sqlite3://#{@path}" do |db|
+				db.exec "delete from queue where status = (?)", status.to_i
+			end
+		end
+		def count_status(status : JobStatus)
+			DB.open "sqlite3://#{@path}" do |db|
+				return db.query_one "select count(*) from queue where status = (?)",
+					status.to_i, as: Int32
+			end
+		end
+		def count
+			DB.open "sqlite3://#{@path}" do |db|
+				return db.query_one "select count(*) from queue", as: Int32
+			end
+		end
+	end
+end