build.rs

extern crate zoneinfo_parse;

use zoneinfo_parse::line::Line;
use zoneinfo_parse::table::{TableBuilder, Table};
use zoneinfo_parse::transitions::TableTransitions;
use zoneinfo_parse::structure::{Structure, Child};
use zoneinfo_parse::transitions::FixedTimespan;

use std::env;
use std::path::Path;
use std::fs::File;
use std::io::{BufRead, BufReader, Write};
use std::collections::BTreeSet;

// This function is needed until zoneinfo_parse handles comments correctly.
// Technically a '#' symbol could occur between double quotes and should be
// ignored in this case, however this never happens in the tz database as it
// stands.
fn strip_comments(mut line: String) -> String {
    line.find('#').map(|pos| line.truncate(pos));
    line
}

// Generate a list of the time zone periods beyond the first that apply
// to this zone, as a string representation of a static slice.
fn format_rest(rest: Vec<(i64, FixedTimespan)>) -> String {
    let mut ret = "&[\n".to_string();
    for (start, FixedTimespan { utc_offset, dst_offset, name }) in rest {
        ret.push_str(&format!(
    "                    ({start}, FixedTimespan {{ utc_offset: {utc}, dst_offset: {dst}, name: \"{name}\" }}),\n",
            start = start,
            utc = utc_offset,
            dst = dst_offset,
            name = name,
        ));
    }
    ret.push_str("                ]");
    ret
}

// Convert all '/' to '__', all '+' to 'Plus' and '-' to 'Minus', unless
// it's a hyphen, in which case remove it. This is so the names can be used
// as rust identifiers.
fn convert_bad_chars(name: &str) -> String {
    let name = name.replace("/", "__").replace("+", "Plus");
    if let Some(pos) = name.find('-') {
        if name[pos+1..].chars().next().map(char::is_numeric).unwrap_or(false) {
            name.replace("-", "Minus")
        } else {
            name.replace("-", "")
        }
    } else {
        name
    }
}

// The timezone file contains impls of `Timespans` for all timezones in the
// database. The `Wrap` wrapper in the `timezone_impl` module then implements
// TimeZone for any contained struct that implements `Timespans`.
fn write_timezone_file(timezone_file: &mut File, table: &Table) {
    let zones = table.zonesets.keys().chain(table.links.keys()).collect::<BTreeSet<_>>();
    write!(timezone_file, "use ::timezone_impl::{{TimeSpans, FixedTimespanSet, FixedTimespan}};\n",).unwrap();
    write!(timezone_file, "use std::fmt::{{Debug, Formatter, Error}};\n\n",).unwrap();
    write!(timezone_file, "use std::str::FromStr;\n\n",).unwrap();
    write!(timezone_file, "#[derive(Clone, Copy, PartialEq, Eq)]\npub enum Tz {{\n").unwrap();
    for zone in &zones {
        let zone_name = convert_bad_chars(zone);
        write!(timezone_file, "    {zone},\n", zone = zone_name).unwrap();
    }
    write!(timezone_file, "}}\n\n").unwrap();

    write!(timezone_file,
"impl FromStr for Tz {{
    type Err = String;
    fn from_str(s: &str) -> Result<Self, String> {{
        match s {{\n").unwrap();
    for zone in &zones {
        let zone_name = convert_bad_chars(zone);
        write!(timezone_file,
               "            \"{raw_zone_name}\" => Ok(Tz::{zone}),\n",
               zone = zone_name,
               raw_zone_name = zone).unwrap();
    }
    write!(timezone_file, 
"             s => Err(s.to_string())
        }}
    }}
}}\n\n").unwrap();

    write!(timezone_file,
"impl Debug for Tz {{
    fn fmt(&self, f: &mut Formatter) -> Result<(), Error> {{
        match *self {{\n").unwrap();
    for zone in &zones {
        let zone_name = convert_bad_chars(zone);
        write!(timezone_file,
               "            Tz::{zone} => write!(f, \"{raw_zone_name}\"),\n",
               zone = zone_name,
               raw_zone_name = zone).unwrap();
    }
    write!(timezone_file,
"         }}
    }}
}}\n\n").unwrap();
    write!(timezone_file,
"impl TimeSpans for Tz {{
    fn timespans(&self) -> FixedTimespanSet {{
        match *self {{\n").unwrap();
    for zone in &zones {
        let timespans = table.timespans(&zone).unwrap();
        let zone_name = convert_bad_chars(zone);
        write!(
            timezone_file, 
"            Tz::{zone} => {{
                const REST: &'static [(i64, FixedTimespan)] = {rest};
                FixedTimespanSet {{
                    first: FixedTimespan {{
                        utc_offset: {utc},
                        dst_offset: {dst},
                        name: \"{name}\",
                    }},
                    rest: REST
                }}
            }},\n\n",
            zone = zone_name,
            rest = format_rest(timespans.rest),
            utc = timespans.first.utc_offset,
            dst = timespans.first.dst_offset,
            name = timespans.first.name,
        ).unwrap();
    }
    write!(timezone_file,
"         }}
    }}
}}\n").unwrap();
}

// Create a file containing nice-looking re-exports such as Europe::London
// instead of having to use chrono_tz::timezones::Europe__London
fn write_directory_file(directory_file: &mut File, table: &Table) {

    // add the `loose' zone definitions first at the top of the file
    write!(directory_file, "use timezones::Tz;\n\n").unwrap();
    let zones = table.zonesets.keys().chain(table.links.keys())
                .filter(|zone| !zone.contains('/'))
                .collect::<BTreeSet<_>>();
    for zone in zones {
        let zone = convert_bad_chars(zone);
        write!(directory_file,
              "pub const {name} : Tz = Tz::{name};\n",
              name = zone).unwrap();
    }
    write!(directory_file, "\n").unwrap();

    // now add the `structured' zone names in submodules
    for entry in table.structure() {
        if entry.name.contains('/') { continue; }
        let module_name = convert_bad_chars(entry.name);
        write!(directory_file, "pub mod {name} {{\n", name = module_name).unwrap();
        write!(directory_file, "    use timezones::Tz;\n\n",).unwrap();
        for child in entry.children {
            match child {
                Child::Submodule(name) => {
                    let submodule_name = convert_bad_chars(name);
                    write!(directory_file, "    pub mod {name} {{\n", name = submodule_name).unwrap();
                    write!(directory_file, "        use timezones::Tz;\n\n",).unwrap();
                    let full_name = entry.name.to_string() + "/" + name;
                    for entry in table.structure() {
                        if entry.name == full_name {
                            for child in entry.children {
                                match child {
                                    Child::Submodule(_) => panic!("Depth of > 3 nested submodules not implemented!"),
                                    Child::TimeZone(name) => {
                                        let converted_name = convert_bad_chars(name);
                                        write!(directory_file,
                                    "        pub const {name} : Tz = Tz::{module_name}__{submodule_name}__{name};\n",
                                            module_name = module_name,
                                            submodule_name = submodule_name,
                                            name = converted_name,
                                        ).unwrap();
                                    }
                                }
                            }
                        }
                    }
                    write!(directory_file, "    }}\n\n").unwrap();
                },
                Child::TimeZone(name) => {
                    let name = convert_bad_chars(name);
                    write!(directory_file,
                          "    pub const {name} : Tz = Tz::{module_name}__{name};\n",
                          module_name = module_name,
                          name = name).unwrap();
                }
            }
        }
        write!(directory_file, "}}\n\n").unwrap();
    }
}

fn main() {
    let mut table = TableBuilder::new();

    let tzfiles = [
        "tz/africa",
        "tz/antarctica",
        "tz/asia",
        "tz/australasia",
        "tz/backward",
        "tz/etcetera",
        "tz/europe",
        "tz/northamerica",
        "tz/pacificnew",
        "tz/southamerica",
    ];

    let lines = tzfiles.iter()
        .map(Path::new)
        .map(File::open)
        .map(Result::unwrap)
        .map(BufReader::new)
        .flat_map(BufRead::lines)
        .map(Result::unwrap)
        .map(strip_comments);

    for line in lines {
        match Line::from_str(&line).unwrap() {
            Line::Zone(zone) => table.add_zone_line(zone).unwrap(),
            Line::Continuation(cont) => table.add_continuation_line(cont).unwrap(),
            Line::Rule(rule) => table.add_rule_line(rule).unwrap(),
            Line::Link(link) => table.add_link_line(link).unwrap(),
            Line::Space => {},
        }
    }
    let table = table.build();
    let timezone_path = Path::new(&env::var("OUT_DIR").unwrap()).join("timezones.rs");
    let mut timezone_file = File::create(&timezone_path).unwrap();
    write_timezone_file(&mut timezone_file, &table);
    let directory_path = Path::new(&env::var("OUT_DIR").unwrap()).join("directory.rs");
    let mut directory_file = File::create(&directory_path).unwrap();
    write_directory_file(&mut directory_file, &table);
}