From 63eda6d69c2e5b1f8a89c00bacb77d3e54adee96 Mon Sep 17 00:00:00 2001
From: Emi Simpson <emi@alchemi.dev>
Date: Fri, 10 Feb 2023 14:50:34 -0500
Subject: [PATCH] Add ability to read in elevation data

---
 read_in.py | 124 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 124 insertions(+)
 create mode 100644 read_in.py

diff --git a/read_in.py b/read_in.py
new file mode 100644
index 0000000..309577a
--- /dev/null
+++ b/read_in.py
@@ -0,0 +1,124 @@
+from emis_funky_funktions import *
+
+from itertools import chain
+from typing import List, NamedTuple
+
+def meters_to_millimeters(meters: float) -> int:
+	"""
+	Convert meters (floating point) to millimeters (int)
+
+	>>> meters_to_millimeters(1.9333473e+02)
+	193334
+
+	>>> meters_to_millimeters(1.0)
+	1000
+	"""
+	return int(1000 * meters)
+
+def read_single_elevation(dat: str) -> Result[int, str]:
+	"""
+	Read in a single elevation
+
+	Expects a single, stringified floating point value, in meters, without a unit, e.g.
+	"2.057e+02".  If there is a parsing error, returns an error containing the input
+	string. Otherwise, returns the elevation in millimeters.
+
+	>>> read_single_elevation("1.9333473e+02")
+	Ok(val=193334)
+
+	>>> read_single_elevation("1.0")
+	Ok(val=1000)
+
+	>>> read_single_elevation("10.0m")
+	Err(err='10.0m')
+	"""
+	return map_res(
+		meters_to_millimeters, # fuck floating points
+		try_(replace(dat), float, dat)
+	)
+
+def read_elevation_line(line: str) -> Result[Iterator[int], Tuple[int, str]]:
+	"""
+	Reads a line of elevations
+
+	Each elevation should be in the format specified by `read_single_elevation`.  Every
+	element of the line is parsed and combined into an iterator, which is returned.  If
+	any parsing errors are encountered, the first error is returned.  It takes the form of
+	a tuple containing the column of the error (in terms of whitespace-deliniated words,
+	not characters) and the string which could not be parsed.
+
+	Recall from the definition of `read_single_elevation()` that the return value is an
+	integer number of millimeters.
+
+	As per the problem specification, the last five columns of the line are not read or
+	parsed.  Parsing errors in these columns therefor cannot be encountered, and any data
+	in these columns will not be returned.
+
+	>>> map_res(list, read_elevation_line("1.9e2 18e1 181 179.1 ignored 170.1 1.8e2 18i+2 20e1"))
+	Ok(val=[190000, 180000, 181000, 179100])
+
+	>>> map_res(list, read_elevation_line("1.9e2 18e 181 179.1 ignored 170.1 1.8e2 18i+2 20e1"))
+	Err(err=(2, '18e'))
+	"""
+	return sequence([
+		map_err(
+			lambda err_text: (col_no + 1, err_text),
+			read_single_elevation(elem)
+		)
+		# As per spec, we drop the last five entries of the file.
+		for (col_no, elem) in enumerate(line.split()[:-5])
+	])
+
+class ErrorLocation(NamedTuple):
+	"The location of an error within file"
+
+	line_no: int
+	"The line on which the error occurred"
+
+	col_no: int
+	"The column (1-indexed number of whitespace deliniated words) on which the error occurred"
+
+	invalid_entry: str
+	"The text which failed to parse as a floating point value"
+
+def read_elevations(lines: str) -> Result[Iterator[int], ErrorLocation]:
+	"""
+	Read an entire elevation file into a list
+
+	This parses each line in of the file using `read_elevation_line()`.  Errors
+	encountered are reported using an `ErrorLocation`.  The resulting list is
+	single-dimensional, but can be indexed arbitrarily, meaning for an input file with a
+	constant number of columns per line, this data can be accessed as if it were a 2d
+	square array.
+
+	However, keep in mind that, as with `read_elevation_line()`, the last five columns of
+	each line are dropped/ignored, and are therefor not present in the returned data.
+
+	>>> map_res(list, read_elevations('''
+	... 1   2   3   4   5   6   7   8   9e  10
+	... 11  2.0 3e1 4   5   6   7   bwa 9   10
+	... 11  2.0 3e0 4   5   ign err 8   9   10
+	... '''))
+	Ok(val=[1000, 2000, 3000, 4000, 5000, 11000, 2000, 30000, 4000, 5000, 11000, 2000, 3000, 4000, 5000])
+
+	>>> map_res(list, read_elevations('''
+	... 1   2   3   4   5   6   7   8   9e  10
+	... 11  ERR 3e1 4   5   6   7   bwa 9   10
+	... 11  2.0 3e0 4   5   ign err 8   9   10
+	... '''))
+	Err(err=ErrorLocation(line_no=2, col_no=2, invalid_entry='ERR'))
+	"""
+	return map_res(
+		chain.from_iterable,
+		sequence([
+			map_err(
+				lambda err: ErrorLocation(line_no + 1, *err),
+				read_elevation_line(line)
+			)
+			for (line_no, line) in enumerate(lines.strip().split('\n'))
+		])
+	)
+
+if __name__ == '__main__':
+	import doctest
+	doctest.testmod()
\ No newline at end of file