module main

import os
import flag
import strings

const (
    tool_version     = '0.0.4'
    tool_description = 'Converts a list of arbitrary files into a single v module file.'
)

struct Context {
mut:
    files       []string
    prefix      string
    show_help   bool
    module_name string
    write_file  string
}

fn (context Context) header() string {
    mut header_s := ''
    header_s += 'module ${context.module_name}\n'
    header_s += '\n'
    allfiles := context.files.join(' ')
    mut options := []string{}
    if context.prefix.len > 0 {
        options << '-p ${context.prefix}'
    }
    if context.module_name.len > 0 {
        options << '-m ${context.module_name}'
    }
    if context.write_file.len > 0 {
        options << '-w ${context.write_file}'
    }
    soptions := options.join(' ')
    header_s += '// File generated by:\n'
    header_s += '// v bin2v ${allfiles} ${soptions}\n'
    header_s += '// Please, do not edit this file.\n'
    header_s += '// Your changes may be overwritten.\n'
    header_s += 'const (\n'
    return header_s
}

fn (context Context) footer() string {
    return ')\n'
}

fn (context Context) file2v(bname string, fbytes []u8, bn_max int) string {
    mut sb := strings.new_builder(1000)
    bn_diff_len := bn_max - bname.len
    sb.write_string('\t${bname}_len' + ' '.repeat(bn_diff_len - 4) + ' = ${fbytes.len}\n')
    fbyte := fbytes[0]
    bnmae_line := '\t${bname}' + ' '.repeat(bn_diff_len) + ' = [u8(${fbyte}), '
    sb.write_string(bnmae_line)
    mut line_len := bnmae_line.len + 3
    for i := 1; i < fbytes.len; i++ {
        b := int(fbytes[i]).str()
        if line_len > 94 {
            sb.go_back(1)
            sb.write_string('\n\t\t')
            line_len = 8
        }
        if i == fbytes.len - 1 {
            sb.write_string(b)
            line_len += b.len
        } else {
            sb.write_string('${b}, ')
            line_len += b.len + 2
        }
    }
    sb.write_string(']!\n')
    return sb.str()
}

fn (context Context) bname_and_bytes(file string) !(string, []u8) {
    fname := os.file_name(file)
    fname_escaped := fname.replace_each(['.', '_', '-', '_'])
    byte_name := '${context.prefix}${fname_escaped}'.to_lower()
    fbytes := os.read_bytes(file) or { return error('Error: ${err.msg()}') }
    return byte_name, fbytes
}

fn (context Context) max_bname_len(bnames []string) int {
    mut max := 0
    for n in bnames {
        if n.len > max {
            max = n.len
        }
    }
    // Add 4 to max due to "_len" suffix
    return max + 4
}

fn main() {
    mut context := Context{}
    mut fp := flag.new_flag_parser(os.args[1..])
    fp.application('v bin2v')
    fp.version(tool_version)
    fp.description(tool_description)
    fp.arguments_description('FILE [FILE]...')
    context.show_help = fp.bool('help', `h`, false, 'Show this help screen.')
    context.module_name = fp.string('module', `m`, 'binary', 'Name of the generated module.')
    context.prefix = fp.string('prefix', `p`, '', 'A prefix put before each resource name.')
    context.write_file = fp.string('write', `w`, '', 'Write directly to a file with the given name.')
    if context.show_help {
        println(fp.usage())
        exit(0)
    }
    files := fp.finalize() or {
        eprintln('Error: ${err.msg()}')
        exit(1)
    }
    real_files := files.filter(it != 'bin2v')
    if real_files.len == 0 {
        println(fp.usage())
        exit(0)
    }
    context.files = real_files
    if context.write_file != '' && os.file_ext(context.write_file) !in ['.vv', '.v'] {
        context.write_file += '.v'
    }
    mut file_byte_map := map[string][]u8{}
    for file in real_files {
        bname, fbytes := context.bname_and_bytes(file) or {
            eprintln(err.msg())
            exit(1)
        }
        file_byte_map[bname] = fbytes
    }
    max_bname := context.max_bname_len(file_byte_map.keys())
    if context.write_file.len > 0 {
        mut out_file := os.create(context.write_file)!
        out_file.write_string(context.header())!
        for bname, fbytes in file_byte_map {
            out_file.write_string(context.file2v(bname, fbytes, max_bname))!
        }
        out_file.write_string(context.footer())!
    } else {
        print(context.header())
        for bname, fbytes in file_byte_map {
            print(context.file2v(bname, fbytes, max_bname))
        }
        print(context.footer())
    }
}