// Copyright (c) 2021 Lars Pontoppidan. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
module toml

import toml.ast
import toml.input
import toml.scanner
import toml.parser

// Null is used in sumtype checks as a "default" value when nothing else is possible.
pub struct Null {
}

// decode decodes a TOML `string` into the target type `T`.
// If `T` has a custom `.from_toml()` method, it will be used instead of the default.
pub fn decode[T](toml_txt string) !T {
    doc := parse_text(toml_txt)!
    mut typ := T{}
    $for method in T.methods {
        $if method.name == 'from_toml' {
            typ.$method(doc.to_any())
            return typ
        }
    }
    $if T !is $struct {
        return error('toml.decode: expected struct, found ${T.name}')
    }
    decode_struct[T](doc.to_any(), mut typ)
    return typ
}

fn decode_struct[T](doc Any, mut typ T) {
    $for field in T.fields {
        value := doc.value(field.name)
        $if field.is_enum {
            typ.$(field.name) = value.int()
        } $else $if field.typ is string {
            typ.$(field.name) = value.string()
        } $else $if field.typ is bool {
            typ.$(field.name) = value.bool()
        } $else $if field.typ is int {
            typ.$(field.name) = value.int()
        } $else $if field.typ is i64 {
            typ.$(field.name) = value.i64()
        } $else $if field.typ is u64 {
            typ.$(field.name) = value.u64()
        } $else $if field.typ is f32 {
            typ.$(field.name) = value.f32()
        } $else $if field.typ is f64 {
            typ.$(field.name) = value.f64()
        } $else $if field.typ is DateTime {
            typ.$(field.name) = value.datetime()
        } $else $if field.typ is Date {
            typ.$(field.name) = value.date()
        } $else $if field.typ is Time {
            typ.$(field.name) = value.time()
        } $else $if field.is_array {
            arr := value.array()
            match typeof(typ.$(field.name)).name {
                '[]string' { typ.$(field.name) = arr.as_strings() }
                '[]int' { typ.$(field.name) = arr.map(it.int()) }
                '[]i64' { typ.$(field.name) = arr.map(it.i64()) }
                '[]u64' { typ.$(field.name) = arr.map(it.u64()) }
                '[]f32' { typ.$(field.name) = arr.map(it.f32()) }
                '[]f64' { typ.$(field.name) = arr.map(it.f64()) }
                '[]bool' { typ.$(field.name) = arr.map(it.bool()) }
                '[]toml.DateTime' { typ.$(field.name) = arr.map(it.datetime()) }
                '[]toml.Date' { typ.$(field.name) = arr.map(it.date()) }
                '[]toml.Time' { typ.$(field.name) = arr.map(it.time()) }
                else {}
            }
        } $else $if field.is_struct {
            mut s := typ.$(field.name)
            decode_struct(value, mut s)
            typ.$(field.name) = s
        }
    }
}

// encode encodes the type `T` into a TOML string.
// If `T` has a custom `.to_toml()` method, it will be used instead of the default.
pub fn encode[T](typ T) string {
    $for method in T.methods {
        $if method.name == 'to_toml' {
            return typ.$method()
        }
    }
    mp := encode_struct[T](typ)
    return mp.to_toml()
}

fn encode_struct[T](typ T) map[string]Any {
    mut mp := map[string]Any{}
    $for field in T.fields {
        value := typ.$(field.name)
        $if field.is_enum {
            mp[field.name] = Any(int(value))
        } $else $if field.is_struct {
            mp[field.name] = encode_struct(value)
        } $else $if field.is_array {
            mut arr := []Any{}
            for v in value {
                $if v is Date {
                    arr << Any(v)
                } $else $if v is Time {
                    arr << Any(v)
                } $else $if v is DateTime {
                    arr << Any(v)
                } $else $if v is $struct {
                    arr << Any(encode(v))
                } $else {
                    arr << Any(v)
                }
            }
            mp[field.name] = arr
        } $else {
            mp[field.name] = Any(value)
        }
    }
    return mp
}

// DateTime is the representation of an RFC 3339 datetime string.
pub struct DateTime {
    datetime string
}

// str returns the RFC 3339 string representation of the datetime.
pub fn (dt DateTime) str() string {
    return dt.datetime
}

// Date is the representation of an RFC 3339 date-only string.
pub struct Date {
    date string
}

// str returns the RFC 3339 date-only string representation.
pub fn (d Date) str() string {
    return d.date
}

// Time is the representation of an RFC 3339 time-only string.
pub struct Time {
    time string
}

// str returns the RFC 3339 time-only string representation.
pub fn (t Time) str() string {
    return t.time
}

// Config is used to configure the toml parser.
// Only one of the fields `text` or `file_path`, is allowed to be set at time of configuration.
pub struct Config {
pub:
    text           string // TOML text
    file_path      string // '/path/to/file.toml'
    parse_comments bool
}

// Doc is a representation of a TOML document.
// A document can be constructed from a `string` buffer or from a file path
pub struct Doc {
pub:
    ast &ast.Root = unsafe { nil }
}

// parse_file parses the TOML file in `path`.
pub fn parse_file(path string) !Doc {
    input_config := input.Config{
        file_path: path
    }
    scanner_config := scanner.Config{
        input: input_config
    }
    parser_config := parser.Config{
        scanner: scanner.new_scanner(scanner_config)!
    }
    mut p := parser.new_parser(parser_config)
    ast_ := p.parse()!
    return Doc{
        ast: ast_
    }
}

// parse_text parses the TOML document provided in `text`.
pub fn parse_text(text string) !Doc {
    input_config := input.Config{
        text: text
    }
    scanner_config := scanner.Config{
        input: input_config
    }
    parser_config := parser.Config{
        scanner: scanner.new_scanner(scanner_config)!
    }
    mut p := parser.new_parser(parser_config)
    ast_ := p.parse()!
    return Doc{
        ast: ast_
    }
}

// parse_dotted_key converts `key` string to an array of strings.
// parse_dotted_key preserves strings delimited by both `"` and `'`.
pub fn parse_dotted_key(key string) ![]string {
    mut out := []string{}
    mut buf := ''
    mut in_string := false
    mut delim := u8(` `)
    for ch in key {
        if ch in [`"`, `'`] {
            if !in_string {
                delim = ch
            }
            in_string = !in_string && ch == delim
            if !in_string {
                if buf != '' && buf != ' ' {
                    out << buf
                }
                buf = ''
                delim = ` `
            }
            continue
        }
        buf += ch.ascii_str()
        if !in_string && ch == `.` {
            if buf != '' && buf != ' ' {
                buf = buf[..buf.len - 1]
                if buf != '' && buf != ' ' {
                    out << buf
                }
            }
            buf = ''
            continue
        }
    }
    if buf != '' && buf != ' ' {
        out << buf
    }
    if in_string {
        return error(@FN +
            ': could not parse key, missing closing string delimiter `${delim.ascii_str()}`')
    }
    return out
}

// parse_array_key converts `key` string to a key and index part.
fn parse_array_key(key string) (string, int) {
    mut index := -1
    mut k := key
    if k.contains('[') {
        index = k.all_after('[').all_before(']').int()
        if k.starts_with('[') {
            k = '' // k.all_after(']')
        } else {
            k = k.all_before('[')
        }
    }
    return k, index
}

// decode decodes a TOML `string` into the target struct type `T`.
pub fn (d Doc) decode[T]() !T {
    $if T !is $struct {
        return error('Doc.decode: expected struct, found ${T.name}')
    }
    mut typ := T{}
    decode_struct(d.to_any(), mut typ)
    return typ
}

// to_any converts the `Doc` to toml.Any type.
pub fn (d Doc) to_any() Any {
    return ast_to_any(d.ast.table)
}

// reflect returns `T` with `T.<field>`'s value set to the
// value of any 1st level TOML key by the same name.
pub fn (d Doc) reflect[T]() T {
    return d.to_any().reflect[T]()
}

// value queries a value from the TOML document.
// `key` supports a small query syntax scheme:
// Maps can be queried in "dotted" form e.g. `a.b.c`.
// quoted keys are supported as `a."b.c"` or `a.'b.c'`.
// Arrays can be queried with `a[0].b[1].[2]`.
pub fn (d Doc) value(key string) Any {
    key_split := parse_dotted_key(key) or { return toml.null }
    return d.value_(d.ast.table, key_split)
}

pub const null = Any(Null{})

// value_opt queries a value from the TOML document. Returns an error if the
// key is not valid or there is no value for the key.
pub fn (d Doc) value_opt(key string) !Any {
    key_split := parse_dotted_key(key) or { return error('invalid dotted key') }
    x := d.value_(d.ast.table, key_split)
    if x is Null {
        return error('no value for key')
    }
    return x
}

// value_ returns the value found at `key` in the map `values` as `Any` type.
fn (d Doc) value_(value ast.Value, key []string) Any {
    if key.len == 0 {
        return toml.null
    }
    mut ast_value := ast.Value(ast.Null{})
    k, index := parse_array_key(key[0])

    if k == '' {
        a := value as []ast.Value
        ast_value = a[index] or { return toml.null }
    }

    if value is map[string]ast.Value {
        ast_value = value[k] or { return toml.null }
        if index > -1 {
            a := ast_value as []ast.Value
            ast_value = a[index] or { return toml.null }
        }
    }

    if key.len <= 1 {
        return ast_to_any(ast_value)
    }
    match ast_value {
        map[string]ast.Value, []ast.Value {
            return d.value_(ast_value, key[1..])
        }
        else {
            return ast_to_any(value)
        }
    }
}

// ast_to_any converts `from` ast.Value to toml.Any value.
pub fn ast_to_any(value ast.Value) Any {
    match value {
        ast.Date {
            return Any(Date{value.text})
        }
        ast.Time {
            return Any(Time{value.text})
        }
        ast.DateTime {
            return Any(DateTime{value.text})
        }
        ast.Quoted {
            return Any(value.text)
        }
        ast.Number {
            val_text := value.text
            if val_text == 'inf' || val_text == '+inf' || val_text == '-inf' {
                // NOTE values taken from strconv
                if !val_text.starts_with('-') {
                    // strconv.double_plus_infinity
                    return Any(u64(0x7FF0000000000000))
                } else {
                    // strconv.double_minus_infinity
                    return Any(u64(0xFFF0000000000000))
                }
            }
            if val_text == 'nan' || val_text == '+nan' || val_text == '-nan' {
                return Any('nan')
            }
            if !val_text.starts_with('0x')
                && (val_text.contains('.') || val_text.to_lower().contains('e')) {
                return Any(value.f64())
            }
            return Any(value.i64())
        }
        ast.Bool {
            str := (value as ast.Bool).text
            if str == 'true' {
                return Any(true)
            }
            return Any(false)
        }
        map[string]ast.Value {
            m := (value as map[string]ast.Value)
            mut am := map[string]Any{}
            for k, v in m {
                am[k] = ast_to_any(v)
            }
            return am
            // return d.get_map_value(m, key_split[1..].join('.'))
        }
        []ast.Value {
            a := (value as []ast.Value)
            mut aa := []Any{}
            for val in a {
                aa << ast_to_any(val)
            }
            return aa
        }
        else {
            return toml.null
        }
    }

    return toml.null
    // TODO decide this
    // panic(@MOD + '.' + @STRUCT + '.' + @FN + ' can\'t convert "$value"')
    // return Any('')
}