use std::path::{Path, PathBuf};
use std::sync::Arc;
use std::io;

use anyhow::{anyhow, Context, Result};
use rayon::prelude::*;
use walkdir::WalkDir;

use crate::config::Settings;
use crate::fsops::{self, CollisionPolicy, OpMode};
use crate::llm::{LlmClient, LlmHints};
use crate::media;
use crate::metadata::{MatchOutcome, MetadataClient, MovieMetadata, Provider, ScoredCandidate};
use crate::output::{Output, StatusKind};
use crate::parse::{parse_filename, FileHints};
use crate::report::{summarize_candidates, Report, ReportEntry};
use crate::utils::{sanitize_filename, Semaphore};

pub fn run(mut settings: Settings) -> Result<Report> {
    ensure_ffprobe()?;

    let output = Arc::new(Output::new(&settings.color, settings.verbose));
    if settings.no_lookup {
        output.warn("No-lookup mode enabled: using filename/LLM only (no external providers).");
    }
    if settings.verbose {
        output.info(&format!(
            "jobs: {} | net-jobs: {} | report format: {:?}",
            settings.jobs, settings.net_jobs, settings.report_format
        ));
    }

    if settings.interactive {
        settings.jobs = 1;
        settings.net_jobs = settings.net_jobs.max(1);
    }

    let files = discover_files(&settings.input, &settings.output)?;
    let total = files.len();
    if total == 0 {
        output.warn("no video files found");
        return Ok(Report::default());
    }

    let settings = Arc::new(settings);
    let net_sem = Arc::new(Semaphore::new(settings.net_jobs));
    let metadata = if settings.no_lookup {
        None
    } else {
        let client = Arc::new(MetadataClient::new(settings.clone(), net_sem)?);
        client.validate()?;
        Some(client)
    };

    let llm = build_llm_client(&settings, &output)?;

    let pool = rayon::ThreadPoolBuilder::new()
        .num_threads(settings.jobs)
        .build()
        .context("failed to build thread pool")?;

    let results: Vec<ReportEntry> = pool.install(|| {
        files
            .par_iter()
            .enumerate()
            .map(|(idx, path)| {
                process_file(
                    idx + 1,
                    total,
                    path,
                    settings.clone(),
                    metadata.clone(),
                    llm.clone(),
                    output.clone(),
                )
                .unwrap_or_else(|err| ReportEntry {
                    input: path.display().to_string(),
                    status: "failed".to_string(),
                    provider: None,
                    result: None,
                    output: None,
                    reason: Some(err.to_string()),
                    candidates: Vec::new(),
                })
            })
            .collect()
    });

    let mut report = Report::default();
    for entry in results {
        report.record(entry);
    }

    Ok(report)
}

fn ensure_ffprobe() -> Result<()> {
    let output = std::process::Command::new("ffprobe")
        .arg("-version")
        .output();
    match output {
        Ok(output) if output.status.success() => Ok(()),
        _ => Err(anyhow!(
            "ffprobe not found. Please install ffmpeg/ffprobe and ensure it is in PATH."
        )),
    }
}

fn discover_files(input: &Path, output: &Path) -> Result<Vec<PathBuf>> {
    let mut files = Vec::new();
    for entry in WalkDir::new(input).follow_links(true) {
        let entry = entry?;
        if !entry.file_type().is_file() {
            continue;
        }
        let path = entry.path();
        if output != input && path.starts_with(output) {
            continue;
        }
        if is_video_file(path) {
            files.push(path.to_path_buf());
        }
    }
    Ok(files)
}

fn is_video_file(path: &Path) -> bool {
    let ext = match path.extension().and_then(|e| e.to_str()) {
        Some(ext) => ext.to_ascii_lowercase(),
        None => return false,
    };
    matches!(
        ext.as_str(),
        "mkv" | "mp4" | "avi" | "mov" | "m4v" | "mpg" | "mpeg" | "wmv" | "webm" | "ts" | "m2ts"
    )
}

fn process_file(
    index: usize,
    total: usize,
    path: &Path,
    settings: Arc<Settings>,
    metadata: Option<Arc<MetadataClient>>,
    llm: Option<Arc<LlmClient>>,
    output: Arc<Output>,
) -> Result<ReportEntry> {
    let filename = path.file_name().unwrap_or_default().to_string_lossy().to_string();
    let mut hints = parse_filename(path);

    if let Some(llm) = &llm {
        if settings.llm.mode != crate::cli::LlmMode::Off {
            if let Ok(llm_hints) = llm.parse_filename(&filename) {
                merge_llm_hints(&mut hints, llm_hints, settings.llm.mode.clone());
            } else {
                output.warn(&format!("LLM parse failed for {filename}, using heuristic parse"));
            }
        }
    }

    let media = match media::probe(path) {
        Ok(info) => info,
        Err(err) => {
            output.status_line(
                index,
                total,
                StatusKind::Failed,
                &filename,
                None,
                "ffprobe failed",
                None,
            );
            return Ok(ReportEntry {
                input: path.display().to_string(),
                status: "failed".to_string(),
                provider: None,
                result: None,
                output: None,
                reason: Some(err.to_string()),
                candidates: Vec::new(),
            });
        }
    };

    let runtime_minutes = media
        .duration_seconds
        .map(|seconds| (seconds / 60.0).round() as u32);

    let outcome = if settings.no_lookup {
        MatchOutcome {
            best: match_offline(&hints, settings.interactive)?,
            candidates: Vec::new(),
        }
    } else {
        match metadata
            .as_ref()
            .ok_or_else(|| anyhow!("metadata client unavailable"))?
            .match_movie(&hints, runtime_minutes)
        {
            Ok(outcome) => outcome,
            Err(err) => {
                output.status_line(
                    index,
                    total,
                    StatusKind::Failed,
                    &filename,
                    None,
                    "metadata lookup failed",
                    None,
                );
                return Ok(ReportEntry {
                    input: path.display().to_string(),
                    status: "failed".to_string(),
                    provider: None,
                    result: None,
                    output: None,
                    reason: Some(err.to_string()),
                    candidates: Vec::new(),
                });
            }
        }
    };

    let mut chosen = outcome.best.clone();
    if settings.interactive && !settings.no_lookup {
        let client = metadata.as_ref().ok_or_else(|| anyhow!("metadata client unavailable"))?;
        chosen = interactive_choice(&outcome, path, client)?;
    }

    if chosen.is_none() {
        let reason = if settings.no_lookup {
            if hints.title.is_none() || hints.year.is_none() {
                "no-lookup missing title/year".to_string()
            } else {
                "no-lookup skipped".to_string()
            }
        } else {
            "no match above threshold".to_string()
        };
        output.status_line(
            index,
            total,
            StatusKind::Skipped,
            &filename,
            None,
            "no match",
            None,
        );
        let entry = ReportEntry {
            input: path.display().to_string(),
            status: "skipped".to_string(),
            provider: None,
            result: None,
            output: None,
            reason: Some(reason),
            candidates: summarize_candidates(&outcome.candidates, 3),
        };
        if settings.sidecar_notes {
            write_sidecar_note(path, &entry)?;
        }
        return Ok(entry);
    }

    let metadata = chosen.unwrap();
    let quality = media::quality_tag(&media, &settings.quality_tags);
    let output_path = build_output_path(&metadata, &settings, path, quality.as_deref());

    if settings.dry_run {
        output.status_line(
            index,
            total,
            StatusKind::Renamed,
            &filename,
            Some(metadata.provider.as_str()),
            "dry-run",
            Some(&output_path.display().to_string()),
        );
        return Ok(ReportEntry {
            input: path.display().to_string(),
            status: "renamed".to_string(),
            provider: Some(metadata.provider.as_str().to_string()),
            result: Some(format!("{} ({})", metadata.title, metadata.year)),
            output: Some(output_path.display().to_string()),
            reason: Some("dry-run".to_string()),
            candidates: Vec::new(),
        });
    }

    let op_mode = if settings.move_files {
        OpMode::Move
    } else if settings.rename_in_place {
        OpMode::RenameInPlace
    } else {
        OpMode::Copy
    };
    let policy = if settings.overwrite {
        CollisionPolicy::Overwrite
    } else if settings.suffix {
        CollisionPolicy::Suffix
    } else {
        CollisionPolicy::Skip
    };

    let outcome = fsops::execute(path, &output_path, op_mode, policy, settings.sidecars)?;
    if outcome.final_path.is_none() {
        output.status_line(
            index,
            total,
            StatusKind::Skipped,
            &filename,
            Some(metadata.provider.as_str()),
            "destination exists",
            None,
        );
        let entry = ReportEntry {
            input: path.display().to_string(),
            status: "skipped".to_string(),
            provider: Some(metadata.provider.as_str().to_string()),
            result: Some(format!("{} ({})", metadata.title, metadata.year)),
            output: None,
            reason: outcome.skipped_reason,
            candidates: Vec::new(),
        };
        if settings.sidecar_notes {
            write_sidecar_note(path, &entry)?;
        }
        return Ok(entry);
    }

    let final_path = outcome.final_path.unwrap();
    output.status_line(
        index,
        total,
        StatusKind::Renamed,
        &filename,
        Some(metadata.provider.as_str()),
        "renamed",
        Some(&final_path.display().to_string()),
    );

    Ok(ReportEntry {
        input: path.display().to_string(),
        status: "renamed".to_string(),
        provider: Some(metadata.provider.as_str().to_string()),
        result: Some(format!("{} ({})", metadata.title, metadata.year)),
        output: Some(final_path.display().to_string()),
        reason: None,
        candidates: Vec::new(),
    })
}

fn merge_llm_hints(hints: &mut FileHints, llm_hints: LlmHints, mode: crate::cli::LlmMode) {
    if let Some(title) = llm_hints.title {
        if hints.title.is_none() || mode == crate::cli::LlmMode::Parse {
            hints.title = Some(title.clone());
            hints.normalized_title = Some(crate::utils::normalize_title(&title));
        } else if hints.title.as_deref() != Some(title.as_str()) {
            hints.alt_titles.push(title);
        }
    }
    if let Some(year) = llm_hints.year {
        if hints.year.is_none() || mode == crate::cli::LlmMode::Parse {
            hints.year = Some(year);
        }
    }
    if !llm_hints.alt_titles.is_empty() {
        hints.alt_titles.extend(llm_hints.alt_titles);
    }
}

fn match_offline(hints: &FileHints, interactive: bool) -> Result<Option<MovieMetadata>> {
    if let (Some(title), Some(year)) = (&hints.title, hints.year) {
        return Ok(Some(MovieMetadata {
            title: title.clone(),
            year,
            tmdb_id: None,
            imdb_id: None,
            provider: Provider::Parsed,
            runtime_minutes: None,
        }));
    }

    if interactive {
        let title = prompt("Title")?;
        let year = prompt("Year")?;
        if let Ok(year) = year.parse::<i32>() {
            return Ok(Some(MovieMetadata {
                title,
                year,
                tmdb_id: None,
                imdb_id: None,
                provider: Provider::Manual,
                runtime_minutes: None,
            }));
        }
    }
    Ok(None)
}

fn build_output_path(
    metadata: &MovieMetadata,
    settings: &Settings,
    source: &Path,
    quality: Option<&str>,
) -> PathBuf {
    let mut folder = format!("{} ({})", metadata.title, metadata.year);
    folder = sanitize_filename(&folder);

    let mut filename = folder.clone();
    if let Some(quality) = quality {
        filename.push_str(&format!(" [{}]", quality));
    }
    if settings.include_id {
        if let Some(id) = id_tag(metadata) {
            filename.push_str(&format!(" [{}]", id));
        }
    }

    let ext = source.extension().and_then(|e| e.to_str()).unwrap_or("");
    if !ext.is_empty() {
        filename.push('.');
        filename.push_str(ext);
    }

    settings.output.join(folder).join(filename)
}

fn id_tag(metadata: &MovieMetadata) -> Option<String> {
    match metadata.provider {
        Provider::Tmdb => metadata.tmdb_id.map(|id| format!("tmdb-{id}")),
        Provider::Omdb => metadata.imdb_id.as_ref().map(|id| format!("imdb-{id}")),
        Provider::Parsed | Provider::Manual => None,
    }
}

fn interactive_choice(
    outcome: &MatchOutcome,
    path: &Path,
    metadata: &MetadataClient,
) -> Result<Option<MovieMetadata>> {
    if outcome.candidates.is_empty() {
        return Ok(outcome.best.clone());
    }

    let ambiguous = is_ambiguous(&outcome.candidates);
    if !ambiguous && outcome.best.is_some() {
        return Ok(outcome.best.clone());
    }

    let filename = path.file_name().unwrap_or_default().to_string_lossy();
    println!("Ambiguous match for {filename}");
    for (idx, candidate) in outcome.candidates.iter().take(3).enumerate() {
        let label = format!(
            "  {}) {} ({}) [{}] score {:.1}",
            idx + 1,
            candidate.candidate.title,
            candidate.candidate.year.unwrap_or(0),
            candidate.candidate.provider.as_str(),
            candidate.score * 100.0
        );
        println!("{label}");
    }
    println!("  s) skip");
    println!("  m) manual title/year");
    print!("Choose: ");
    io::Write::flush(&mut std::io::stdout())?;

    let mut choice = String::new();
    std::io::stdin().read_line(&mut choice)?;
    let choice = choice.trim();
    if choice.eq_ignore_ascii_case("s") {
        return Ok(None);
    }
    if choice.eq_ignore_ascii_case("m") {
        let title = prompt("Title")?;
        let year = prompt("Year")?;
        if let Ok(year) = year.parse::<i32>() {
            return Ok(Some(MovieMetadata {
                title,
                year,
                tmdb_id: None,
                imdb_id: None,
                provider: Provider::Manual,
                runtime_minutes: None,
            }));
        }
        return Ok(None);
    }
    if let Ok(index) = choice.parse::<usize>() {
        if let Some(candidate) = outcome.candidates.get(index - 1) {
            if let Ok(details) = metadata.resolve_candidate(&candidate.candidate) {
                return Ok(Some(details));
            }
            return Ok(Some(MovieMetadata {
                title: candidate.candidate.title.clone(),
                year: candidate.candidate.year.unwrap_or(0),
                tmdb_id: None,
                imdb_id: None,
                provider: candidate.candidate.provider.clone(),
                runtime_minutes: None,
            }));
        }
    }
    Ok(outcome.best.clone())
}

fn is_ambiguous(candidates: &[ScoredCandidate]) -> bool {
    if candidates.len() < 2 {
        return false;
    }
    (candidates[0].score - candidates[1].score).abs() < 0.02
}

fn prompt(label: &str) -> Result<String> {
    print!("{label}: ");
    io::Write::flush(&mut std::io::stdout())?;
    let mut input = String::new();
    std::io::stdin().read_line(&mut input)?;
    Ok(input.trim().to_string())
}

fn build_llm_client(settings: &Settings, output: &Output) -> Result<Option<Arc<LlmClient>>> {
    if settings.llm.mode == crate::cli::LlmMode::Off {
        return Ok(None);
    }
    let model = match &settings.llm.model {
        Some(model) => model.clone(),
        None => {
            output.warn("LLM mode enabled but no model provided; disabling LLM");
            return Ok(None);
        }
    };
    let client = LlmClient::new(
        settings.llm.endpoint.clone(),
        model,
        settings.llm.timeout_seconds,
        settings.llm.max_tokens,
    )?;
    Ok(Some(Arc::new(client)))
}

fn write_sidecar_note(path: &Path, entry: &ReportEntry) -> Result<()> {
    let note_path = path.with_extension("mov-renamarr.txt");
    let mut note = String::new();
    note.push_str(&format!("Status: {}\n", entry.status));
    if let Some(reason) = &entry.reason {
        note.push_str(&format!("Reason: {}\n", reason));
    }
    if !entry.candidates.is_empty() {
        note.push_str("Candidates:\n");
        for candidate in &entry.candidates {
            note.push_str(&format!(
                "  - {} ({}) [{}] {:.1}\n",
                candidate.title,
                candidate.year.unwrap_or(0),
                candidate.provider,
                candidate.score * 100.0
            ));
        }
    }
    std::fs::write(&note_path, note)
        .with_context(|| format!("failed to write sidecar note: {}", note_path.display()))?;
    Ok(())
}