'wtd generate [week]' command builds

3 files changed, 105 insertions, 24 deletions

diff --git a/src/main.rs b/src/main.rs
index 06431e8..ea29cb7 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,5 @@
+use std::io::Write;
+use std::fs::OpenOptions;
 use std::env;
 use chrono::{Local, Duration, Datelike};
 
@@ -11,6 +13,22 @@ mod md_calendar;
 use md_calendar::*;
 mod dates;
 use dates::*;
+mod prune;
+use prune::*;
+
+// https://doc.rust-lang.org/std/fs/struct.File.html
+// https://doc.rust-lang.org/book/ch12-01-accepting-command-line-arguments.html
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    let str_args: Vec<&str> = args.iter().map(String::as_str).collect();
+    match str_args[..] {
+        [_, "html"] => command_html(),
+        [_, "describe", week] => command_describe(&week),
+        [_, "generate", week] => command_generate(&week),
+        [_, "validate"] => command_validate(),
+        _ => panic!("Invalid command. Valid commands are: html, describe [week], generate [week], and validate.")
+    }
+}
 
 fn command_html() {
     /* Pull tasks from:
@@ -32,25 +50,36 @@ fn command_html() {
 }
 
 fn command_describe(week: &str) {
+    println!("{}", internal_describe(week));
+}
+
+fn command_generate(week: &str) {
+    /* This command basically does two things:
+     * 1) wtd describe [week] > [week].md
+     * 2) Prune all tasks from this week from wtd.md
+     */
+    let new_week_file_contents = internal_describe(week);
     let first_date
         = parse_week_str(week).expect("Invalid week string provided. Should be, e.g., jan_24_2022");
     if first_date.weekday().number_from_monday() != 1 { // 1-based, for some reason.
         panic!("The provided week should start on a Monday.");
     }
-    let last_date = first_date + Duration::days(6); // inclusive
-
-    let paths = relevant_files(&first_date, &last_date);
-    let mut tasks: Vec<Task> = vec![];
-    for path in paths {
-        tasks.append(&mut tasks_from_path(&path));
-    }
-
-    let md = tasks_to_md(&tasks, first_date, last_date);
-    println!("{}", md);
+    let new_wtd_contents = prune_week_from_file(first_date, "wtd.md");
+    let week_file_name = first_date.format("%b_%d_%Y.md").to_string().to_lowercase();
+    overwrite_file(&week_file_name, &new_week_file_contents);
+    overwrite_file("wtd.md", &new_wtd_contents);
 }
 
-fn command_generate(week: &str) {
-    // TODO
+fn overwrite_file(name: &str, contents: &str) {
+    let mut file = match OpenOptions::new().create(true).write(true).truncate(true).open(name) {
+        Err(why) => panic!("Error opening {}: {}", name, why),
+        Ok(file) => file,
+    };
+
+    match file.write_all(contents.as_bytes()) {
+        Err(why) => panic!("Couldn't write to {}: {}", name, why),
+        Ok(_) => {},
+    };
 }
 
 fn command_validate() {
@@ -81,16 +110,19 @@ fn command_validate() {
     }
 }
 
-// https://doc.rust-lang.org/std/fs/struct.File.html
-// https://doc.rust-lang.org/book/ch12-01-accepting-command-line-arguments.html
-fn main() {
-    let args: Vec<String> = env::args().collect();
-    let str_args: Vec<&str> = args.iter().map(String::as_str).collect();
-    match str_args[..] {
-        [_, "html"] => command_html(),
-        [_, "describe", week] => command_describe(&week),
-        [_, "generate", week] => command_generate(&week),
-        [_, "validate"] => command_validate(),
-        _ => panic!("Invalid command. Valid commands are: html, describe [week], generate [week], and validate.")
+fn internal_describe(week: &str) -> String {
+    let first_date
+        = parse_week_str(week).expect("Invalid week string provided. Should be, e.g., jan_24_2022");
+    if first_date.weekday().number_from_monday() != 1 { // 1-based, for some reason.
+        panic!("The provided week should start on a Monday.");
+    }
+    let last_date = first_date + Duration::days(6); // inclusive
+
+    let paths = relevant_files(&first_date, &last_date);
+    let mut tasks: Vec<Task> = vec![];
+    for path in paths {
+        tasks.append(&mut tasks_from_path(&path));
     }
+
+    return tasks_to_md(&tasks, first_date, last_date);
 }
diff --git a/src/parse.rs b/src/parse.rs
index 876b861..6bed4d9 100644
--- a/src/parse.rs
+++ b/src/parse.rs
@@ -75,7 +75,7 @@ fn parse_file_str(file_str: &str, implicit_week: Option<NaiveDate>) -> Vec<Task>
     return tasks;
 }
 
-fn parse_date_line(l: &str) -> Option<NaiveDate> {
+pub fn parse_date_line(l: &str) -> Option<NaiveDate> {
     for maybe_date_str in l.split(' ') {
         if let Ok(date) = NaiveDate::parse_from_str(maybe_date_str, "%m/%d/%y") {
             return Some(date);
diff --git a/src/prune.rs b/src/prune.rs
new file mode 100644
index 0000000..dd7a5fb
--- /dev/null
+++ b/src/prune.rs
@@ -0,0 +1,49 @@
+use std::path::Path;
+use std::fs::File;
+use std::io::prelude::*;
+use chrono::{NaiveDate, Duration};
+
+use crate::parse::*;
+
+pub fn prune_week_from_file(week: NaiveDate, file_str: &str) -> String {
+    let path = Path::new(file_str);
+    let display = path.display();
+
+    // Open the path in read-only mode, returns `io::Result<File>`
+    let mut file = match File::open(&path) {
+        Err(why) => panic!("Error opening {}: {}", display, why),
+        Ok(file) => file,
+    };
+
+    // Read the file contents into a string, returns `io::Result<usize>`
+    let mut s = String::new();
+    match file.read_to_string(&mut s) {
+        Err(why) => panic!("Couldn't read {}: {}", display, why),
+        Ok(_) => return prune_week_from_str(week, &s),
+    }
+}
+
+fn prune_week_from_str(week: NaiveDate, file_str: &str) -> String {
+    let mut new_contents = "\n".to_string();
+    let mut ghost = false;
+    let ghost_start = week - Duration::days(6);
+    let ghost_end = week + Duration::days(6);
+    for l in file_str.split('\n') {
+        if l.starts_with("# ") {
+            // '# 12/27/21', starts a new week block
+            let start_date = parse_date_line(l).expect("Couldn't parse '# ' header.");
+            ghost = ghost_start <= start_date && start_date <= ghost_end;
+            if ghost && start_date != week {
+                panic!("generate currently assumes `# ` headers always start on Mondays.");
+            }
+        }
+        if !ghost {
+            new_contents.push_str(l);
+            new_contents.push('\n');
+        }
+    }
+    // Remove leading & trailing newlines.
+    new_contents.remove(0);
+    new_contents.pop();
+    return new_contents;
+}