use std::fs;
use std::path::Path;
use std::process::Command;

use chrono::Utc;

use crate::config::Settings;
use crate::error::StreamdError;
use crate::localize::TaskConfiguration;
use crate::models::LocalizedShard;
use crate::query::find_shard_by_position;

use super::load_markdown_shards;

pub fn collect_open_tasks(show_future: bool) -> Result<Vec<LocalizedShard>, StreamdError> {
    let settings = Settings::load()?;
    let all_shards = load_markdown_shards(
        Path::new(&settings.base_folder),
        &TaskConfiguration,
        chrono_tz::UTC,
    )?;
    let now = Utc::now();

    let mut tasks: Vec<LocalizedShard> = find_shard_by_position(&all_shards, "task", "open")
        .into_iter()
        .filter(|shard| show_future || shard.moment <= now)
        .collect();

    // Sort by moment ascending (oldest first = task 1)
    tasks.sort_by(|a, b| a.moment.cmp(&b.moment));

    Ok(tasks)
}

pub fn run_list(show_future: bool) -> Result<(), StreamdError> {
    let tasks = collect_open_tasks(show_future)?;

    for (index, task_shard) in tasks.iter().enumerate() {
        let task_number = index + 1; // 1-indexed
        if let Some(file_path) = task_shard.location.get("file") {
            let content = fs::read_to_string(file_path)?;
            let lines: Vec<&str> = content.lines().collect();

            let start = task_shard.start_line.saturating_sub(1);
            let end = std::cmp::min(task_shard.end_line, lines.len());

            println!(
                "[{}] --- {}:{} ---",
                task_number, file_path, task_shard.start_line
            );
            for line in &lines[start..end] {
                println!("{}", line);
            }
            println!();
        }
    }

    Ok(())
}

pub fn run_edit(number: usize) -> Result<(), StreamdError> {
    // Always include all tasks for edit (user might want to edit a future task)
    let tasks = collect_open_tasks(true)?;

    if number == 0 || number > tasks.len() {
        return Err(StreamdError::InvalidTaskNumber(number, tasks.len()));
    }

    let task = &tasks[number - 1]; // Convert to 0-indexed
    let file_path = task
        .location
        .get("file")
        .ok_or(StreamdError::MissingFilePath)?;

    let editor = std::env::var("EDITOR").unwrap_or_else(|_| "vi".to_string());
    let line_arg = format!("+{}", task.start_line);

    let status = Command::new(&editor)
        .arg(&line_arg)
        .arg(file_path)
        .status()?;

    if !status.success() {
        return Err(StreamdError::IoError(std::io::Error::other(
            "Editor exited with non-zero status",
        )));
    }

    Ok(())
}

pub fn run_done(number: usize) -> Result<(), StreamdError> {
    // Always include all tasks for done (user might want to mark a future task as done)
    let tasks = collect_open_tasks(true)?;

    if number == 0 || number > tasks.len() {
        return Err(StreamdError::InvalidTaskNumber(number, tasks.len()));
    }

    let task = &tasks[number - 1];
    let file_path = task
        .location
        .get("file")
        .ok_or(StreamdError::MissingFilePath)?;

    let content = fs::read_to_string(file_path)?;
    let mut lines: Vec<String> = content.lines().map(String::from).collect();

    // Find the line containing @Task (should be at start_line)
    let task_line_idx = task.start_line.saturating_sub(1);
    if task_line_idx >= lines.len() {
        return Err(StreamdError::InvalidLineNumber);
    }

    let line = &lines[task_line_idx];

    // Check for multiple @Task occurrences
    let task_count = line.matches("@Task").count();
    if task_count > 1 {
        return Err(StreamdError::MultipleTaskMarkers(
            file_path.clone(),
            task.start_line,
        ));
    }
    if task_count == 0 {
        return Err(StreamdError::NoTaskMarker(
            file_path.clone(),
            task.start_line,
        ));
    }

    // Insert @Done after @Task
    let new_line = line.replacen("@Task", "@Task @Done", 1);
    lines[task_line_idx] = new_line;

    // Write back to file, preserving trailing newline if present
    let new_content = if content.ends_with('\n') {
        format!("{}\n", lines.join("\n"))
    } else {
        lines.join("\n")
    };
    fs::write(file_path, new_content)?;

    println!("Marked task {} as done", number);

    Ok(())
}

pub fn run() -> Result<(), StreamdError> {
    run_list(false)
}

#[cfg(test)]
mod tests {
    use super::*;
    use chrono::{Duration, TimeZone};
    use indexmap::IndexMap;

    fn make_task_shard(moment: chrono::DateTime<Utc>, file: &str) -> LocalizedShard {
        let mut location = IndexMap::new();
        location.insert("file".to_string(), file.to_string());
        location.insert("task".to_string(), "open".to_string());

        LocalizedShard {
            markers: vec!["Task".to_string()],
            tags: vec![],
            start_line: 1,
            end_line: 1,
            moment,
            location,
            children: vec![],
        }
    }

    #[test]
    fn test_insert_done_after_task() {
        let line = "Some content @Task with more text";
        let result = line.replacen("@Task", "@Task @Done", 1);
        assert_eq!(result, "Some content @Task @Done with more text");
    }

    #[test]
    fn test_insert_done_at_line_end() {
        let line = "Some content @Task";
        let result = line.replacen("@Task", "@Task @Done", 1);
        assert_eq!(result, "Some content @Task @Done");
    }

    #[test]
    fn test_insert_done_only_first_task() {
        let line = "Some @Task content @Task again";
        let result = line.replacen("@Task", "@Task @Done", 1);
        assert_eq!(result, "Some @Task @Done content @Task again");
    }

    #[test]
    fn test_task_count_single() {
        let line = "Some content @Task with more text";
        assert_eq!(line.matches("@Task").count(), 1);
    }

    #[test]
    fn test_task_count_multiple() {
        let line = "Some @Task content @Task again";
        assert_eq!(line.matches("@Task").count(), 2);
    }

    #[test]
    fn test_task_count_none() {
        let line = "Some content without task marker";
        assert_eq!(line.matches("@Task").count(), 0);
    }

    #[test]
    fn test_filter_future_tasks_excludes_future_when_show_future_false() {
        let now = Utc::now();
        let past = now - Duration::hours(1);
        let future = now + Duration::hours(1);

        let tasks = vec![
            make_task_shard(past, "past.md"),
            make_task_shard(future, "future.md"),
        ];

        let filtered: Vec<_> = tasks
            .into_iter()
            .filter(|shard| shard.moment <= now)
            .collect();

        assert_eq!(filtered.len(), 1);
        assert_eq!(filtered[0].location.get("file").unwrap(), "past.md");
    }

    #[test]
    fn test_filter_future_tasks_includes_all_when_show_future_true() {
        let now = Utc::now();
        let past = now - Duration::hours(1);
        let future = now + Duration::hours(1);

        let tasks = vec![
            make_task_shard(past, "past.md"),
            make_task_shard(future, "future.md"),
        ];

        let filtered: Vec<_> = tasks.into_iter().filter(|_| true).collect();

        assert_eq!(filtered.len(), 2);
    }

    #[test]
    fn test_sort_tasks_by_moment_ascending() {
        let oldest = Utc.with_ymd_and_hms(2020, 1, 1, 0, 0, 0).unwrap();
        let middle = Utc.with_ymd_and_hms(2021, 1, 1, 0, 0, 0).unwrap();
        let newest = Utc.with_ymd_and_hms(2022, 1, 1, 0, 0, 0).unwrap();

        let mut tasks = [
            make_task_shard(newest, "newest.md"),
            make_task_shard(oldest, "oldest.md"),
            make_task_shard(middle, "middle.md"),
        ];

        tasks.sort_by(|a, b| a.moment.cmp(&b.moment));

        assert_eq!(tasks[0].location.get("file").unwrap(), "oldest.md");
        assert_eq!(tasks[1].location.get("file").unwrap(), "middle.md");
        assert_eq!(tasks[2].location.get("file").unwrap(), "newest.md");
    }

    #[test]
    fn test_preserve_trailing_newline() {
        let content_with_newline = "line1\nline2\n";
        let content_without_newline = "line1\nline2";

        assert!(content_with_newline.ends_with('\n'));
        assert!(!content_without_newline.ends_with('\n'));
    }

    #[test]
    fn test_invalid_task_number_zero() {
        let result = StreamdError::InvalidTaskNumber(0, 5);
        assert_eq!(
            result.to_string(),
            "Invalid task number 0: only 5 tasks available"
        );
    }

    #[test]
    fn test_invalid_task_number_exceeds_count() {
        let result = StreamdError::InvalidTaskNumber(10, 3);
        assert_eq!(
            result.to_string(),
            "Invalid task number 10: only 3 tasks available"
        );
    }

    #[test]
    fn test_multiple_task_markers_error_message() {
        let result = StreamdError::MultipleTaskMarkers("/path/file.md".to_string(), 42);
        assert_eq!(
            result.to_string(),
            "Multiple @Task markers found in /path/file.md:42 - cannot auto-insert @Done"
        );
    }

    #[test]
    fn test_no_task_marker_error_message() {
        let result = StreamdError::NoTaskMarker("/path/file.md".to_string(), 42);
        assert_eq!(
            result.to_string(),
            "No @Task marker found in /path/file.md:42"
        );
    }
}