# A tokenizer of octal, decimal, hexadecimal and floating point numbers
# =====================================================================

import Automa
import Automa.RegExp: @re_str
const re = Automa.RegExp

# Describe patterns in regular expression.
oct      = re"0o[0-7]+"
dec      = re"[-+]?[0-9]+"
hex      = re"0x[0-9A-Fa-f]+"
prefloat = re"[-+]?([0-9]+\.[0-9]*|[0-9]*\.[0-9]+)"
float    = prefloat | re.cat(prefloat | re"[-+]?[0-9]+", re"[eE][-+]?[0-9]+")
number   = oct | dec | hex | float
numbers  = re.cat(re.opt(number), re.rep(re" +" * number), re" *")

# Register action names to regular expressions.
number.actions[:enter] = [:mark]
oct.actions[:exit]     = [:oct]
dec.actions[:exit]     = [:dec]
hex.actions[:exit]     = [:hex]
float.actions[:exit]   = [:float]

# Compile a finite-state machine.
machine = Automa.compile(numbers)

# This generates a SVG file to visualize the state machine.
# write("numbers.dot", Automa.machine2dot(machine))
# run(`dot -Tpng -o numbers.png numbers.dot`)

# Bind an action code for each action name.
actions = Dict(
    :mark  => :(mark = p),
    :oct   => :(emit(:oct)),
    :dec   => :(emit(:dec)),
    :hex   => :(emit(:hex)),
    :float => :(emit(:float)),
)

# Generate a tokenizing function from the machine.
context = Automa.CodeGenContext()
@eval function tokenize(data::String)
    tokens = Tuple{Symbol,String}[]
    mark = 0
    $(Automa.generate_init_code(context, machine))
    p_end = p_eof = lastindex(data)
    emit(kind) = push!(tokens, (kind, data[mark:p-1]))
    $(Automa.generate_exec_code(context, machine, actions))
    return tokens, cs == 0 ? :ok : cs < 0 ? :error : :incomplete
end

tokens, status = tokenize("1 0x0123BEEF 0o754 3.14 -1e4 +6.022045e23")