Create basic ddi parser (#13)

* added test data files to package.

* added EzXML to IPUMS.jl file.

* created ddi_parser.jl file, and added include and export to IPUMs.jl file.

* added test cases for ddi parser.

* added EzXML to Project.toml and removed extraneous print statement from ddi_parser.jl

* moved structs to structs.jl, and added docstrings.

* moved xpath constants to constants.jl file and added documentation.

* updated project.toml with my email addesss. Changing file type test as per request.

* added throw to the ArgumentError.

* added documentation to the loops. added a test case to check whether files existence causes error.

* got preliminary regex stuff working. Need to test.

* added a test case for the data summary. added more documentation.

* added backticks to DDIInfo in docs.

* escape the double dashes.

* fixed some documentation formatting, and added ns testcase.

* indicated in parse_ddi() function that the user should look at docs on DDIInfo for more info.

* re-added small check functions.

* adjusted struct documentation example to reflect updated API.

* Fixed typos and reviewed documentation

---------

Co-authored-by: TheCedarPrince <[email protected]>

Project.toml

@@ -1,11 +1,12 @@
 name = "IPUMS"
 uuid = "51d1f77e-d457-4c14-a89d-9ed71839f38d"
-authors = ["TheCedarPrince <[email protected]> and Krishna Bhogaonker"]
+authors = ["TheCedarPrince <[email protected]> and Krishna Bhogaonker <[email protected]>"]
 version = "0.0.1"
 
 [deps]
 DataFrames = "a93c6f00-e57d-5684-b7b6-d8193f3e46c0"
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
+EzXML = "8f5d6c58-4d21-5cfd-889c-e3ad7ee6a615"
 HTTP = "cd3eb016-35fb-5094-929b-558a96fad6f3"
 JSON3 = "0f8b85d8-7281-11e9-16c2-39a750bddbf1"
 OpenAPI = "d5e62ea6-ddf3-4d43-8e4c-ad5e6c8bfd7d"

src/IPUMS.jl

@@ -13,7 +13,8 @@ module IPUMS
         Client
     using TimeZones
     using URIs
-
+    using EzXML
+
     include("structs.jl")
     include("constants.jl")
     include("helpers.jl")
@@ -30,6 +31,7 @@ module IPUMS
     include("modelincludes.jl")
     include("apis/api_DefaultApi.jl")
     include("piracy.jl")
+    include("parsers/ddi_parser.jl")
 
     #=
         export from_json
@@ -57,5 +59,5 @@ module IPUMS
 
     export Client
     export DefaultApi
-
+    export parse_ddi
 end

src/constants.jl

@@ -88,3 +88,59 @@ const global ipums_sources = [
         collection_type = "microdata"
     )
 ]
+
+
+#=
+
+XPaths for parsing DDI XML files
+
+This is a list of XPATHs for locating file-level and variable-level metadata 
+in a DDI XML file. The constants are stored here, but used in the `ddi_parser.jl`
+file.
+
+Extract level XPATHs:
+
+EXTRACT_CONDITIONS - IPUMS conditions for fair and legal use of public data.
+EXTRACT_CITATION - Citation information for referencing IPUMS data
+EXTRACT_IPUMS_PROJECT - Name of the IPUMS project from which the data is taken, such as CPS, or DHS, etc.
+EXTRACT_NOTES - User provided notes or additional miscellaneous information provided about the extract.
+EXTRACT_DATE - The date that the extract was generated.
+
+Variable level XPATHs:
+
+VAR_NODE_LOCATION = The base nodes that correspond to each variable in the dataset. 
+VAR_NAME_XPATH = The name of the IPUMS variable.
+VAR_STARTPOS_XPATH = The start position (in text columns) of the variable in a fixed width file specification.
+VAR_ENDPOS_XPATH = The end position (in text columns) of the variable in a fixed width file specification.
+VAR_WIDTH_XPATH = The width postion (in text columns) of variable in a fixed width file specification. 
+VAR_LABL_XPATH = A short description for the data contained in a variable.
+VAR_TXT_XPATH = A longer and more complete description of the data contained in a variable.
+VAR_DCML_XPATH = The number of decimal points contained in a variable.
+VAR_TYPE_XPATH = An indicator of whether the variable is either a string or numeric data type.
+VAR_INTERVAL_XPATH = An indicator of whether a numeric variable is continuous or discrete.
+VAR_CATEGORY_XPATH = A description of the category levels and corresponding numerical values for a categorical variable, such as 
+                        "Women => 0, Men => 1"
+
+=#
+
+const EXTRACT_CONDITIONS = "/x:codeBook/x:stdyDscr/x:dataAccs/x:useStmt/x:conditions"
+const EXTRACT_CITATION = "/x:codeBook/x:stdyDscr/x:dataAccs/x:useStmt/x:citReq"
+const EXTRACT_IPUMS_PROJECT = "/x:codeBook/x:stdyDscr/x:citation/x:serStmt/x:serName"
+const EXTRACT_NOTES = "/x:codeBook/x:stdyDscr/x:notes"
+const EXTRACT_DATE = "/x:codeBook/x:stdyDscr/x:citation/x:prodStmt/x:prodDate/@date"
+
+const VAR_NODE_LOCATION = "/x:codeBook/x:dataDscr/x:var"
+const VAR_NAME_XPATH = "/x:codeBook/x:dataDscr/x:var/@name"
+const VAR_STARTPOS_XPATH = "/x:codeBook/x:dataDscr/x:var/x:location/@StartPos"
+const VAR_ENDPOS_XPATH = "/x:codeBook/x:dataDscr/x:var/x:location/@EndPos"
+const VAR_WIDTH_XPATH = "/x:codeBook/x:dataDscr/x:var/x:location/@width"
+const VAR_LABL_XPATH = "/x:codeBook/x:dataDscr/x:var/x:labl"
+const VAR_TXT_XPATH = "/x:codeBook/x:dataDscr/x:var/x:txt"
+const VAR_DCML_XPATH = "/x:codeBook/x:dataDscr/x:var/@dcml"
+const VAR_TYPE_XPATH = "/x:codeBook/x:dataDscr/x:var/x:varFormat/@type"
+const VAR_INTERVAL_XPATH = "/x:codeBook/x:dataDscr/x:var/@intrvl"
+const VAR_CATEGORY_XPATH = "/x:codeBook/x:dataDscr/x:var/x:catgry"
+
+
+
+