Lofi_Generator/lib/audio/songStructure.ts

import { Genre, SectionType } from '@/types/audio';

export interface SongSection {
  type: SectionType;
  bars: number;
  instruments: {
    drums: { active: boolean; volume: number };
    bass: { active: boolean; volume: number };
    brass: { active: boolean; volume: number };
    piano: { active: boolean; volume: number };
    chords: { active: boolean; volume: number };
    ambient: { active: boolean; volume: number };
  };
}

export interface SongStructure {
  sections: SongSection[];
  totalBars: number;
}

// Genre-specific section configurations
const sectionConfigs: Record<SectionType, {
  instruments: SongSection['instruments'];
}> = {
  intro: {
    instruments: {
      drums: { active: false, volume: 0 },
      bass: { active: false, volume: 0 },
      brass: { active: false, volume: 0 },
      piano: { active: true, volume: 0.3 },
      chords: { active: true, volume: 0.4 },
      ambient: { active: true, volume: 0.6 },
    },
  },
  verse: {
    instruments: {
      drums: { active: true, volume: 0.6 },
      bass: { active: true, volume: 0.5 },
      brass: { active: false, volume: 0 },
      piano: { active: true, volume: 0.4 },
      chords: { active: true, volume: 0.5 },
      ambient: { active: true, volume: 0.4 },
    },
  },
  bridge: {
    instruments: {
      drums: { active: true, volume: 0.4 },
      bass: { active: true, volume: 0.4 },
      brass: { active: true, volume: 0.3 },
      piano: { active: false, volume: 0 },
      chords: { active: true, volume: 0.6 },
      ambient: { active: true, volume: 0.5 },
    },
  },
  chorus: {
    instruments: {
      drums: { active: true, volume: 0.8 },
      bass: { active: true, volume: 0.7 },
      brass: { active: true, volume: 0.5 },
      piano: { active: true, volume: 0.5 },
      chords: { active: true, volume: 0.7 },
      ambient: { active: true, volume: 0.3 },
    },
  },
  outro: {
    instruments: {
      drums: { active: true, volume: 0.3 },
      bass: { active: true, volume: 0.3 },
      brass: { active: false, volume: 0 },
      piano: { active: true, volume: 0.4 },
      chords: { active: true, volume: 0.5 },
      ambient: { active: true, volume: 0.7 },
    },
  },
};

// Generate song structure based on duration (in minutes)
export function generateSongStructure(durationMinutes: number, bpm: number, genre: Genre): SongStructure {
  // Calculate total bars based on duration and BPM
  // 4 beats per bar, so bars = (minutes * bpm) / 4
  const totalBars = Math.floor((durationMinutes * bpm) / 4);

  // Create a standard song structure that fits within the total bars
  const sections: SongSection[] = [];

  if (durationMinutes === 1) {
    // Short format: Intro -> Verse -> Chorus -> Outro
    const introBars = Math.floor(totalBars * 0.15);
    const verseBars = Math.floor(totalBars * 0.35);
    const chorusBars = Math.floor(totalBars * 0.35);
    const outroBars = totalBars - introBars - verseBars - chorusBars;

    sections.push({ type: 'intro', bars: introBars, instruments: { ...sectionConfigs.intro.instruments } });
    sections.push({ type: 'verse', bars: verseBars, instruments: { ...sectionConfigs.verse.instruments } });
    sections.push({ type: 'chorus', bars: chorusBars, instruments: { ...sectionConfigs.chorus.instruments } });
    sections.push({ type: 'outro', bars: outroBars, instruments: { ...sectionConfigs.outro.instruments } });
  } else if (durationMinutes === 2) {
    // Medium format: Intro -> Verse -> Bridge -> Chorus -> Outro
    const introBars = Math.floor(totalBars * 0.1);
    const verse1Bars = Math.floor(totalBars * 0.25);
    const bridgeBars = Math.floor(totalBars * 0.15);
    const chorusBars = Math.floor(totalBars * 0.35);
    const outroBars = totalBars - introBars - verse1Bars - bridgeBars - chorusBars;

    sections.push({ type: 'intro', bars: introBars, instruments: { ...sectionConfigs.intro.instruments } });
    sections.push({ type: 'verse', bars: verse1Bars, instruments: { ...sectionConfigs.verse.instruments } });
    sections.push({ type: 'bridge', bars: bridgeBars, instruments: { ...sectionConfigs.bridge.instruments } });
    sections.push({ type: 'chorus', bars: chorusBars, instruments: { ...sectionConfigs.chorus.instruments } });
    sections.push({ type: 'outro', bars: outroBars, instruments: { ...sectionConfigs.outro.instruments } });
  } else {
    // Full format (3+ mins): Intro -> Verse -> Chorus -> Verse -> Bridge -> Chorus -> Outro
    const introBars = Math.floor(totalBars * 0.08);
    const verse1Bars = Math.floor(totalBars * 0.18);
    const chorus1Bars = Math.floor(totalBars * 0.18);
    const verse2Bars = Math.floor(totalBars * 0.15);
    const bridgeBars = Math.floor(totalBars * 0.12);
    const chorus2Bars = Math.floor(totalBars * 0.18);
    const outroBars = totalBars - introBars - verse1Bars - chorus1Bars - verse2Bars - bridgeBars - chorus2Bars;

    sections.push({ type: 'intro', bars: introBars, instruments: { ...sectionConfigs.intro.instruments } });
    sections.push({ type: 'verse', bars: verse1Bars, instruments: { ...sectionConfigs.verse.instruments } });
    sections.push({ type: 'chorus', bars: chorus1Bars, instruments: { ...sectionConfigs.chorus.instruments } });
    sections.push({ type: 'verse', bars: verse2Bars, instruments: { ...sectionConfigs.verse.instruments } });
    sections.push({ type: 'bridge', bars: bridgeBars, instruments: { ...sectionConfigs.bridge.instruments } });
    sections.push({ type: 'chorus', bars: chorus2Bars, instruments: { ...sectionConfigs.chorus.instruments } });
    sections.push({ type: 'outro', bars: outroBars, instruments: { ...sectionConfigs.outro.instruments } });
  }

  // Apply genre-specific modifications
  applyGenreModifications(sections, genre);

  return { sections, totalBars };
}

function applyGenreModifications(sections: SongSection[], genre: Genre): void {
  switch (genre) {
    case 'trap':
      // Trap: heavier bass, more brass in chorus
      sections.forEach(section => {
        if (section.instruments.bass.active) {
          section.instruments.bass.volume = Math.min(1, section.instruments.bass.volume * 1.3);
        }
        if (section.type === 'chorus') {
          section.instruments.brass.volume = Math.min(1, section.instruments.brass.volume * 1.2);
        }
      });
      break;
    case 'classical':
      // Classical: more piano and chords, less drums
      sections.forEach(section => {
        section.instruments.piano.active = true;
        section.instruments.piano.volume = Math.min(1, section.instruments.piano.volume * 1.3);
        section.instruments.drums.volume *= 0.7;
        section.instruments.brass.active = true;
        section.instruments.brass.volume = Math.min(1, section.instruments.brass.volume + 0.2);
      });
      break;
    case 'pop':
      // Pop: balanced, catchy, more emphasis on chorus
      sections.forEach(section => {
        if (section.type === 'chorus') {
          Object.keys(section.instruments).forEach(key => {
            const inst = section.instruments[key as keyof typeof section.instruments];
            inst.volume = Math.min(1, inst.volume * 1.1);
          });
        }
      });
      break;
    case 'hiphop':
    default:
      // Hip hop: heavy drums and bass, soulful samples
      sections.forEach(section => {
        if (section.type === 'verse' || section.type === 'chorus') {
          section.instruments.drums.volume = Math.min(1, section.instruments.drums.volume * 1.1);
          section.instruments.bass.volume = Math.min(1, section.instruments.bass.volume * 1.1);
        }
      });
      break;
  }
}

// Calculate timing for each section in seconds
export function calculateSectionTimings(structure: SongStructure, bpm: number): { startTime: number; endTime: number; section: SongSection }[] {
  const secondsPerBar = (60 / bpm) * 4; // 4 beats per bar
  let currentTime = 0;

  return structure.sections.map(section => {
    const startTime = currentTime;
    const duration = section.bars * secondsPerBar;
    currentTime += duration;
    return {
      startTime,
      endTime: currentTime,
      section,
    };
  });
}