#!/usr/bin/env python3
"""
03-arpeggiator.py - MIDIUtil arpeggiator
Generates automatic ascending/descending arpeggios from chord sets.
Shows clean patterns using MIDIUtil's beat-based time API.
"""
from midiutil import MIDIFile

# ==============================
# Configuration
# ==============================
BPM = 132
PPQ = 960

# Chord definitions: (root MIDI note, number of beats)
# Using A minor progression: Am | F | G | E
CHORDS = [
    {"root": 57, "beats": 4},   # Am  (A3)
    {"root": 53, "beats": 4},   # F   (F3)
    {"root": 55, "beats": 4},   # G   (G3)
    {"root": 52, "beats": 4},   # E   (E3)
]

# Arpeggio patterns: semitone intervals from chord root
CHORD_TYPES = {
    "major":  [0, 4, 7, 12],         # Major triad + octave
    "minor":  [0, 3, 7, 12],         # Minor triad + octave
    "dim":    [0, 3, 6, 9],          # Diminished
    "aug":    [0, 4, 8, 12],         # Augmented
}

# ==============================
# Helper function
# ==============================
def make_arpeggio(midi, track, channel, chord_list,
                  arp_type="minor", arp_direction="up",
                  subdivisions=4, volume=90):
    """
    Generate an arpeggio track from a chord list.
    
    Args:
        midi: MIDIFile object
        track: track index (int)
        channel: MIDI channel (int, 0-15)
        chord_list: list of {"root": M, "beats": N} with MIDI root notes
        arp_type: chord type key for CHORD_TYPES dict ("minor", "major", etc.)
        arp_direction: "up" or "down" for arpeggio direction
        subdivisions: 16th-note speed (4 = standard 16ths, 8 = 32nds)
        volume: note velocity (0-127)
    """
    notes = CHORD_TYPES[arp_type].copy()
    if arp_direction == "down":
        notes = notes[::-1]
    
    note_beats = 1.0 / subdivisions  # duration per arpeggio hit
    
    beat = 0.0
    for chord in chord_list:
        root = chord["root"]
        chord_duration = chord["beats"]
        
        total_hits = int(chord_duration / note_beats)
        for i in range(total_hits):
            note_idx = i % len(notes)
            octave = i // len(notes)
            pitch = root + notes[note_idx] + (octave * 12)
            
            # Cap MIDI pitch range
            pitch = max(0, min(127, pitch))
            
            midi.addNote(track, channel, pitch, beat, note_beats, volume)
            beat += note_beats


# ==============================
# Create multi-track file
# ==============================
midi = MIDIFile(3, file_format=1, ticks_per_quarternote=PPQ)
midi.addTempo(0, 0, BPM)
midi.addTrackName(0, 0, "Arpeggio Lead 1 (Minor)")
midi.addTrackName(1, 0, "Arpeggio Lead 2 (Major)")
midi.addTrackName(2, 0, "Bass")

# Track 0: Upward minor arpeggio (GM 80 - Lead 1 Synth)
midi.addProgramChange(0, 0, 0, 80)
make_arpeggio(midi, 0, 0, CHORDS,
              arp_type="minor", arp_direction="up",
              subdivisions=4, volume=85)

# Track 1: Descending major arpeggio (GM 84 - Lead 3 Synth)
midi.addProgramChange(1, 0, 0, 84)
make_arpeggio(midi, 1, 0, CHORDS,
              arp_type="major", arp_direction="down",
              subdivisions=8, volume=80)

# Track 2: Bass follows chord roots (quarter notes)
midi.addProgramChange(2, 0, 0, 37)  # Synth Bass 1
for chord in CHORDS:
    root = chord["root"]
    chord_duration = chord["beats"]
    
    # Two quarter-note pulses per beat
    for beat_offset in range(0, int(chord_duration * 2)):
        time = beat_offset * 0.5
        midi.addNote(2, 0, root, time, 0.4, 100)
        # Octave pulse for depth
        octave = root + 12
        if octave <= 127:
            midi.addNote(2, 0, octave, time, 0.2, 80)


# ==============================
# Write to Disk
# ==============================
with open("arpeggiator.mid", "wb") as output_file:
    midi.writeFile(output_file)

print("Written: arpeggiator.mid")
print("  3-track arpeggio piece with minor/major contrast")