use core::panic;
use std::fs::{read, write};
use toml::{Table, Value};

fn print_tabs(num: usize) {
    for _ in 0..num {
        print!("  ");
    }
}

fn print_table(table: &Table, depth: usize) {
    for k in table.keys() {
        match table.get(k) {
            Some(v) => match v {
                Value::Table(t) => {
                    print_tabs(depth);
                    println!("{k}:");
                    print_table(&t, depth + 1)
                }
                Value::String(s) => {
                    print_tabs(depth);
                    println!("{k}: {s}");
                }
                Value::Array(a) => {
                    print_tabs(depth);
                    println!("(array){k}:");
                    for element in a {
                        match element {
                            Value::String(s) => println!("  {}", s),
                            _ => todo!(),
                        }
                    }
                }
                _ => continue,
            },
            None => continue,
        }
    }
}

fn target_generator(name: &str, config_table: &Table) -> String {
    let mut ret = String::from("");

    let clang = Value::String(String::from("clang"));
    let blank = Value::String(String::from(""));

    let compiler = match config_table.get("compiler").unwrap_or(&clang) {
        Value::String(s) => s,
        _ => panic!("fatal: {name}.compiler: invalid type (must be string)"),
    };
    let compiler_flags = match config_table.get("compiler_flags").unwrap_or(&blank) {
        Value::String(s) => s,
        _ => panic!("fatal: {name}.compiler_flags: invalid type (must be string)"),
    };
    let linker_flags = match config_table.get("linker_flags").unwrap_or(&blank) {
        Value::String(s) => s,
        _ => panic!("fatal: {name}.linker_flags: invalid type (must be string)"),
    };
    let linker_libs = match config_table.get("linker_libs").unwrap_or(&blank) {
        Value::String(s) => s,
        _ => panic!("fatal: {name}.linker_libs: invalid type (must be string)"),
    };
    let compiler_linker = Value::String(compiler.to_string());
    let linker = match config_table.get("linker").unwrap_or(&compiler_linker) {
        Value::String(s) => s,
        _ => panic!("fatal: {name}.linker: invalid type (must be string)"),
    };

    ret.push_str(&format!(
        r#"# BEGIN TARGET {name}
cflags_{name} = {compiler_flags}
linker_flags_{name} = {linker_flags}
linker_libs_{name} = {linker_libs}
rule cc_{name}
  deps = gcc
  depfile = $out.d
  command = {compiler} $cflags_{name} -MD -MF $out.d -o $out -c $in
  description = Building [{name}] object $out
rule link_{name}
  command = {linker} $linker_flags_{name} -o $out $in $linker_libs_{name}
  description = Linking [{name}] $out

build $builddir/{name}: mkdir
"#
    ));
    let sources = config_table
        .get("sources")
        .unwrap_or_else(|| panic!("fatal: must provide sources"));

    let mut source_list: Vec<String> = Vec::new();

    match sources {
        Value::Array(a) => {
            for elem in a {
                match elem {
                    Value::String(s) => {
                        let obj_name = format!("$builddir/{name}/{s}.o");
                        ret.push_str(&format!(
                            "build {obj_name}: cc_{name} {s} | build.ninja || $builddir/{name}\n"
                        ));
                        source_list.push(obj_name);
                    }
                    _ => panic!(
                        "fatal: element in {name}.sources: invalid source type (must be a string)"
                    ),
                }
            }
        }
        _ => panic!("fatal: {name}.sources: invalid sources type (must be a list of strings)"),
    };

    ret.push_str(&format!("\nbuild $builddir/{name}/{name}: link_{name} "));
    ret.push_str(&source_list.join(" "));
    ret.push_str(&format!(" \nbuild {name}: phony $builddir/{name}/{name}\n"));
    ret.push_str(&format!("# END TARGET {name}\n\n"));

    ret
}

fn main() {
    let conf_file_name = "ngen.toml";
    let conf_file_bytes =
        read(conf_file_name).unwrap_or_else(|e| panic!("fatal: could not read file: {e}"));
    let conf_file = String::from_utf8_lossy(&conf_file_bytes);
    let conf = toml::from_str::<Table>(&conf_file)
        .unwrap_or_else(|e| panic!("fatal: could not parse config file: {e}"));

    let mut ninjafile = String::from(
        r#"builddir = build

rule mkdir
  command = mkdir -p $out
  description = Creating directory $out

rule regen
  command = ngen -f $in
  generator = 1
  description = Regenerating build.ninja

build build.ninja: regen ngen.toml
  pool = console

"#,
    );

    for k in conf.keys() {
        match conf.get(k) {
            Some(v) => match v {
                Value::Table(t) => {
                    //print_table(&t, 0);
                    ninjafile.push_str(&target_generator(&k, &t));
                }
                Value::String(s) => {
                    println!("{k}: {s}");
                }
                _ => continue,
            },
            None => continue,
        }
    }

    write("build.ninja", ninjafile)
        .unwrap_or_else(|e| panic!("fatal: could not write ninja file: {e}"));
}