use crate::io::story_metadata::set_front_matter_field;
use std::collections::HashMap;
use std::fs;
use std::path::Path;

use super::{find_story_file, next_item_number, replace_section_content, slugify_name};

/// Shared create-story logic used by both the OpenApi and MCP handlers.
///
/// When `commit` is `true`, the new story file is git-added and committed to
/// the current branch immediately after creation.
pub fn create_story_file(
    root: &std::path::Path,
    name: &str,
    user_story: Option<&str>,
    acceptance_criteria: Option<&[String]>,
    commit: bool,
) -> Result<String, String> {
    let story_number = next_item_number(root)?;
    let slug = slugify_name(name);

    if slug.is_empty() {
        return Err("Name must contain at least one alphanumeric character.".to_string());
    }

    let filename = format!("{story_number}_story_{slug}.md");
    let backlog_dir = root.join(".storkit").join("work").join("1_backlog");
    fs::create_dir_all(&backlog_dir)
        .map_err(|e| format!("Failed to create backlog directory: {e}"))?;

    let filepath = backlog_dir.join(&filename);
    if filepath.exists() {
        return Err(format!("Story file already exists: {filename}"));
    }

    let story_id = filepath
        .file_stem()
        .and_then(|s| s.to_str())
        .unwrap_or_default()
        .to_string();

    let mut content = String::new();
    content.push_str("---\n");
    content.push_str(&format!("name: \"{}\"\n", name.replace('"', "\\\"")));
    content.push_str("---\n\n");
    content.push_str(&format!("# Story {story_number}: {name}\n\n"));

    content.push_str("## User Story\n\n");
    if let Some(us) = user_story {
        content.push_str(us);
        content.push('\n');
    } else {
        content.push_str("As a ..., I want ..., so that ...\n");
    }
    content.push('\n');

    content.push_str("## Acceptance Criteria\n\n");
    if let Some(criteria) = acceptance_criteria {
        for criterion in criteria {
            content.push_str(&format!("- [ ] {criterion}\n"));
        }
    } else {
        content.push_str("- [ ] TODO\n");
    }
    content.push('\n');

    content.push_str("## Out of Scope\n\n");
    content.push_str("- TBD\n");

    fs::write(&filepath, &content)
        .map_err(|e| format!("Failed to write story file: {e}"))?;

    // Watcher handles the git commit asynchronously.
    let _ = commit; // kept for API compat, ignored

    Ok(story_id)
}

/// Check off the Nth unchecked acceptance criterion in a story file and auto-commit.
///
/// `criterion_index` is 0-based among unchecked (`- [ ]`) items.
pub fn check_criterion_in_file(
    project_root: &Path,
    story_id: &str,
    criterion_index: usize,
) -> Result<(), String> {
    let filepath = find_story_file(project_root, story_id)?;
    let contents = fs::read_to_string(&filepath)
        .map_err(|e| format!("Failed to read story file: {e}"))?;

    let mut unchecked_count: usize = 0;
    let mut found = false;
    let new_lines: Vec<String> = contents
        .lines()
        .map(|line| {
            let trimmed = line.trim();
            if let Some(rest) = trimmed.strip_prefix("- [ ] ") {
                if unchecked_count == criterion_index {
                    unchecked_count += 1;
                    found = true;
                    let indent_len = line.len() - trimmed.len();
                    let indent = &line[..indent_len];
                    return format!("{indent}- [x] {rest}");
                }
                unchecked_count += 1;
            }
            line.to_string()
        })
        .collect();

    if !found {
        return Err(format!(
            "Criterion index {criterion_index} out of range. Story '{story_id}' has \
             {unchecked_count} unchecked criteria (indices 0..{}).",
            unchecked_count.saturating_sub(1)
        ));
    }

    let mut new_str = new_lines.join("\n");
    if contents.ends_with('\n') {
        new_str.push('\n');
    }
    fs::write(&filepath, &new_str)
        .map_err(|e| format!("Failed to write story file: {e}"))?;

    // Watcher handles the git commit asynchronously.
    Ok(())
}

/// Add a new acceptance criterion to a story file.
///
/// Appends `- [ ] {criterion}` after the last existing criterion line in the
/// "## Acceptance Criteria" section, or directly after the section heading if
/// the section is empty. The filesystem watcher auto-commits the change.
pub fn add_criterion_to_file(
    project_root: &Path,
    story_id: &str,
    criterion: &str,
) -> Result<(), String> {
    let filepath = find_story_file(project_root, story_id)?;
    let contents = fs::read_to_string(&filepath)
        .map_err(|e| format!("Failed to read story file: {e}"))?;

    let lines: Vec<&str> = contents.lines().collect();
    let mut in_ac_section = false;
    let mut ac_section_start: Option<usize> = None;
    let mut last_criterion_line: Option<usize> = None;

    for (i, line) in lines.iter().enumerate() {
        let trimmed = line.trim();
        if trimmed == "## Acceptance Criteria" {
            in_ac_section = true;
            ac_section_start = Some(i);
            continue;
        }
        if in_ac_section {
            if trimmed.starts_with("## ") {
                break;
            }
            if trimmed.starts_with("- [ ] ") || trimmed.starts_with("- [x] ") {
                last_criterion_line = Some(i);
            }
        }
    }

    let insert_after = last_criterion_line
        .or(ac_section_start)
        .ok_or_else(|| {
            format!("Story '{story_id}' has no '## Acceptance Criteria' section.")
        })?;

    let mut new_lines: Vec<String> = lines.iter().map(|s| s.to_string()).collect();
    new_lines.insert(insert_after + 1, format!("- [ ] {criterion}"));

    let mut new_str = new_lines.join("\n");
    if contents.ends_with('\n') {
        new_str.push('\n');
    }
    fs::write(&filepath, &new_str)
        .map_err(|e| format!("Failed to write story file: {e}"))?;

    // Watcher handles the git commit asynchronously.
    Ok(())
}

/// Encode a string value as a YAML scalar.
///
/// Booleans (`true`/`false`) and integers are written as native YAML types (unquoted).
/// Everything else is written as a quoted string to avoid ambiguity.
fn yaml_encode_scalar(value: &str) -> String {
    match value {
        "true" | "false" => value.to_string(),
        s if s.parse::<i64>().is_ok() => s.to_string(),
        s => format!("\"{}\"", s.replace('"', "\\\"").replace('\n', " ").replace('\r', "")),
    }
}

/// Update the user story text and/or description in a story file.
///
/// At least one of `user_story` or `description` must be provided.
/// Replaces the content of the corresponding `##` section in place.
/// The filesystem watcher auto-commits the change.
pub fn update_story_in_file(
    project_root: &Path,
    story_id: &str,
    user_story: Option<&str>,
    description: Option<&str>,
    front_matter: Option<&HashMap<String, String>>,
) -> Result<(), String> {
    let has_front_matter_updates = front_matter.map(|m| !m.is_empty()).unwrap_or(false);
    if user_story.is_none() && description.is_none() && !has_front_matter_updates {
        return Err(
            "At least one of 'user_story', 'description', or 'front_matter' must be provided."
                .to_string(),
        );
    }

    let filepath = find_story_file(project_root, story_id)?;
    let mut contents = fs::read_to_string(&filepath)
        .map_err(|e| format!("Failed to read story file: {e}"))?;

    if let Some(fields) = front_matter {
        for (key, value) in fields {
            let yaml_value = yaml_encode_scalar(value);
            contents = set_front_matter_field(&contents, key, &yaml_value);
        }
    }

    if let Some(us) = user_story {
        contents = replace_section_content(&contents, "User Story", us)?;
    }
    if let Some(desc) = description {
        contents = replace_section_content(&contents, "Description", desc)?;
    }

    fs::write(&filepath, &contents)
        .map_err(|e| format!("Failed to write story file: {e}"))?;

    // Watcher handles the git commit asynchronously.
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::io::story_metadata::parse_front_matter;

    fn setup_git_repo(root: &std::path::Path) {
        std::process::Command::new("git")
            .args(["init"])
            .current_dir(root)
            .output()
            .unwrap();
        std::process::Command::new("git")
            .args(["config", "user.email", "test@test.com"])
            .current_dir(root)
            .output()
            .unwrap();
        std::process::Command::new("git")
            .args(["config", "user.name", "Test"])
            .current_dir(root)
            .output()
            .unwrap();
        std::process::Command::new("git")
            .args(["commit", "--allow-empty", "-m", "init"])
            .current_dir(root)
            .output()
            .unwrap();
    }

    fn story_with_criteria(n: usize) -> String {
        let mut s = "---\nname: Test Story\n---\n\n## Acceptance Criteria\n\n".to_string();
        for i in 0..n {
            s.push_str(&format!("- [ ] Criterion {i}\n"));
        }
        s
    }

    // --- create_story integration tests ---

    #[test]
    fn create_story_writes_correct_content() {
        let tmp = tempfile::tempdir().unwrap();
        let backlog = tmp.path().join(".storkit/work/1_backlog");
        fs::create_dir_all(&backlog).unwrap();
        fs::write(backlog.join("36_story_existing.md"), "").unwrap();

        let number = super::super::next_item_number(tmp.path()).unwrap();
        assert_eq!(number, 37);

        let slug = super::super::slugify_name("My New Feature");
        assert_eq!(slug, "my_new_feature");

        let filename = format!("{number}_{slug}.md");
        let filepath = backlog.join(&filename);

        let mut content = String::new();
        content.push_str("---\n");
        content.push_str("name: \"My New Feature\"\n");
        content.push_str("---\n\n");
        content.push_str(&format!("# Story {number}: My New Feature\n\n"));
        content.push_str("## User Story\n\n");
        content.push_str("As a dev, I want this feature\n\n");
        content.push_str("## Acceptance Criteria\n\n");
        content.push_str("- [ ] It works\n");
        content.push_str("- [ ] It is tested\n\n");
        content.push_str("## Out of Scope\n\n");
        content.push_str("- TBD\n");

        fs::write(&filepath, &content).unwrap();

        let written = fs::read_to_string(&filepath).unwrap();
        assert!(written.starts_with("---\nname: \"My New Feature\"\n---"));
        assert!(written.contains("# Story 37: My New Feature"));
        assert!(written.contains("- [ ] It works"));
        assert!(written.contains("- [ ] It is tested"));
        assert!(written.contains("## Out of Scope"));
    }

    #[test]
    fn create_story_with_colon_in_name_produces_valid_yaml() {
        let tmp = tempfile::tempdir().unwrap();
        let name = "Server-owned agent completion: remove report_completion dependency";
        let result = create_story_file(tmp.path(), name, None, None, false);
        assert!(result.is_ok(), "create_story_file failed: {result:?}");

        let backlog = tmp.path().join(".storkit/work/1_backlog");
        let story_id = result.unwrap();
        let filename = format!("{story_id}.md");
        let contents = fs::read_to_string(backlog.join(&filename)).unwrap();

        let meta = parse_front_matter(&contents).expect("front matter should be valid YAML");
        assert_eq!(meta.name.as_deref(), Some(name));
    }

    #[test]
    fn create_story_rejects_duplicate() {
        let tmp = tempfile::tempdir().unwrap();
        let backlog = tmp.path().join(".storkit/work/1_backlog");
        fs::create_dir_all(&backlog).unwrap();

        let filepath = backlog.join("1_story_my_feature.md");
        fs::write(&filepath, "existing").unwrap();

        // Simulate the check
        assert!(filepath.exists());
    }

    // ── check_criterion_in_file tests ─────────────────────────────────────────

    #[test]
    fn check_criterion_marks_first_unchecked() {
        let tmp = tempfile::tempdir().unwrap();
        setup_git_repo(tmp.path());
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        let filepath = current.join("1_test.md");
        fs::write(&filepath, story_with_criteria(3)).unwrap();
        std::process::Command::new("git")
            .args(["add", "."])
            .current_dir(tmp.path())
            .output()
            .unwrap();
        std::process::Command::new("git")
            .args(["commit", "-m", "add story"])
            .current_dir(tmp.path())
            .output()
            .unwrap();

        check_criterion_in_file(tmp.path(), "1_test", 0).unwrap();

        let contents = fs::read_to_string(&filepath).unwrap();
        assert!(contents.contains("- [x] Criterion 0"), "first should be checked");
        assert!(contents.contains("- [ ] Criterion 1"), "second should stay unchecked");
        assert!(contents.contains("- [ ] Criterion 2"), "third should stay unchecked");
    }

    #[test]
    fn check_criterion_marks_second_unchecked() {
        let tmp = tempfile::tempdir().unwrap();
        setup_git_repo(tmp.path());
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        let filepath = current.join("2_test.md");
        fs::write(&filepath, story_with_criteria(3)).unwrap();
        std::process::Command::new("git")
            .args(["add", "."])
            .current_dir(tmp.path())
            .output()
            .unwrap();
        std::process::Command::new("git")
            .args(["commit", "-m", "add story"])
            .current_dir(tmp.path())
            .output()
            .unwrap();

        check_criterion_in_file(tmp.path(), "2_test", 1).unwrap();

        let contents = fs::read_to_string(&filepath).unwrap();
        assert!(contents.contains("- [ ] Criterion 0"), "first should stay unchecked");
        assert!(contents.contains("- [x] Criterion 1"), "second should be checked");
        assert!(contents.contains("- [ ] Criterion 2"), "third should stay unchecked");
    }

    #[test]
    fn check_criterion_out_of_range_returns_error() {
        let tmp = tempfile::tempdir().unwrap();
        setup_git_repo(tmp.path());
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        let filepath = current.join("3_test.md");
        fs::write(&filepath, story_with_criteria(2)).unwrap();
        std::process::Command::new("git")
            .args(["add", "."])
            .current_dir(tmp.path())
            .output()
            .unwrap();
        std::process::Command::new("git")
            .args(["commit", "-m", "add story"])
            .current_dir(tmp.path())
            .output()
            .unwrap();

        let result = check_criterion_in_file(tmp.path(), "3_test", 5);
        assert!(result.is_err(), "should fail for out-of-range index");
        assert!(result.unwrap_err().contains("out of range"));
    }

    // ── add_criterion_to_file tests ───────────────────────────────────────────

    fn story_with_ac_section(criteria: &[&str]) -> String {
        let mut s = "---\nname: Test\n---\n\n## User Story\n\nAs a user...\n\n## Acceptance Criteria\n\n".to_string();
        for c in criteria {
            s.push_str(&format!("- [ ] {c}\n"));
        }
        s.push_str("\n## Out of Scope\n\n- N/A\n");
        s
    }

    #[test]
    fn add_criterion_appends_after_last_criterion() {
        let tmp = tempfile::tempdir().unwrap();
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        let filepath = current.join("10_test.md");
        fs::write(&filepath, story_with_ac_section(&["First", "Second"])).unwrap();

        add_criterion_to_file(tmp.path(), "10_test", "Third").unwrap();

        let contents = fs::read_to_string(&filepath).unwrap();
        assert!(contents.contains("- [ ] First\n"));
        assert!(contents.contains("- [ ] Second\n"));
        assert!(contents.contains("- [ ] Third\n"));
        // Third should come after Second
        let pos_second = contents.find("- [ ] Second").unwrap();
        let pos_third = contents.find("- [ ] Third").unwrap();
        assert!(pos_third > pos_second, "Third should appear after Second");
    }

    #[test]
    fn add_criterion_to_empty_section() {
        let tmp = tempfile::tempdir().unwrap();
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        let filepath = current.join("11_test.md");
        let content = "---\nname: Test\n---\n\n## Acceptance Criteria\n\n## Out of Scope\n\n- N/A\n";
        fs::write(&filepath, content).unwrap();

        add_criterion_to_file(tmp.path(), "11_test", "New AC").unwrap();

        let contents = fs::read_to_string(&filepath).unwrap();
        assert!(contents.contains("- [ ] New AC\n"), "criterion should be present");
    }

    #[test]
    fn add_criterion_missing_section_returns_error() {
        let tmp = tempfile::tempdir().unwrap();
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        let filepath = current.join("12_test.md");
        fs::write(&filepath, "---\nname: Test\n---\n\nNo AC section here.\n").unwrap();

        let result = add_criterion_to_file(tmp.path(), "12_test", "X");
        assert!(result.is_err());
        assert!(result.unwrap_err().contains("Acceptance Criteria"));
    }

    // ── update_story_in_file tests ─────────────────────────────────────────────

    #[test]
    fn update_story_replaces_user_story_section() {
        let tmp = tempfile::tempdir().unwrap();
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        let filepath = current.join("20_test.md");
        let content = "---\nname: T\n---\n\n## User Story\n\nOld text\n\n## Acceptance Criteria\n\n- [ ] AC\n";
        fs::write(&filepath, content).unwrap();

        update_story_in_file(tmp.path(), "20_test", Some("New user story text"), None, None).unwrap();

        let result = fs::read_to_string(&filepath).unwrap();
        assert!(result.contains("New user story text"), "new text should be present");
        assert!(!result.contains("Old text"), "old text should be replaced");
        assert!(result.contains("## Acceptance Criteria"), "other sections preserved");
    }

    #[test]
    fn update_story_replaces_description_section() {
        let tmp = tempfile::tempdir().unwrap();
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        let filepath = current.join("21_test.md");
        let content = "---\nname: T\n---\n\n## Description\n\nOld description\n\n## Acceptance Criteria\n\n- [ ] AC\n";
        fs::write(&filepath, content).unwrap();

        update_story_in_file(tmp.path(), "21_test", None, Some("New description"), None).unwrap();

        let result = fs::read_to_string(&filepath).unwrap();
        assert!(result.contains("New description"), "new description present");
        assert!(!result.contains("Old description"), "old description replaced");
    }

    #[test]
    fn update_story_no_args_returns_error() {
        let tmp = tempfile::tempdir().unwrap();
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        fs::write(current.join("22_test.md"), "---\nname: T\n---\n").unwrap();

        let result = update_story_in_file(tmp.path(), "22_test", None, None, None);
        assert!(result.is_err());
        assert!(result.unwrap_err().contains("At least one"));
    }

    #[test]
    fn update_story_missing_section_returns_error() {
        let tmp = tempfile::tempdir().unwrap();
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        fs::write(
            current.join("23_test.md"),
            "---\nname: T\n---\n\nNo sections here.\n",
        )
        .unwrap();

        let result = update_story_in_file(tmp.path(), "23_test", Some("new text"), None, None);
        assert!(result.is_err());
        assert!(result.unwrap_err().contains("User Story"));
    }

    #[test]
    fn update_story_sets_agent_front_matter_field() {
        let tmp = tempfile::tempdir().unwrap();
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        let filepath = current.join("24_test.md");
        fs::write(&filepath, "---\nname: T\n---\n\n## User Story\n\nSome story\n").unwrap();

        let mut fields = HashMap::new();
        fields.insert("agent".to_string(), "dev".to_string());
        update_story_in_file(tmp.path(), "24_test", None, None, Some(&fields)).unwrap();

        let result = fs::read_to_string(&filepath).unwrap();
        assert!(result.contains("agent: \"dev\""), "agent field should be set");
        assert!(result.contains("name: T"), "name field preserved");
    }

    #[test]
    fn update_story_sets_arbitrary_front_matter_fields() {
        let tmp = tempfile::tempdir().unwrap();
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        let filepath = current.join("25_test.md");
        fs::write(&filepath, "---\nname: T\n---\n\n## User Story\n\nSome story\n").unwrap();

        let mut fields = HashMap::new();
        fields.insert("qa".to_string(), "human".to_string());
        fields.insert("priority".to_string(), "high".to_string());
        update_story_in_file(tmp.path(), "25_test", None, None, Some(&fields)).unwrap();

        let result = fs::read_to_string(&filepath).unwrap();
        assert!(result.contains("qa: \"human\""), "qa field should be set");
        assert!(result.contains("priority: \"high\""), "priority field should be set");
        assert!(result.contains("name: T"), "name field preserved");
    }

    #[test]
    fn update_story_front_matter_only_no_section_required() {
        let tmp = tempfile::tempdir().unwrap();
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        // File without a User Story section — front matter update should succeed
        let filepath = current.join("26_test.md");
        fs::write(&filepath, "---\nname: T\n---\n\nNo sections here.\n").unwrap();

        let mut fields = HashMap::new();
        fields.insert("agent".to_string(), "dev".to_string());
        let result = update_story_in_file(tmp.path(), "26_test", None, None, Some(&fields));
        assert!(result.is_ok(), "front-matter-only update should not require body sections");

        let contents = fs::read_to_string(&filepath).unwrap();
        assert!(contents.contains("agent: \"dev\""));
    }

    #[test]
    fn update_story_bool_front_matter_written_unquoted() {
        let tmp = tempfile::tempdir().unwrap();
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        let filepath = current.join("27_test.md");
        fs::write(&filepath, "---\nname: T\n---\n\nNo sections.\n").unwrap();

        let mut fields = HashMap::new();
        fields.insert("blocked".to_string(), "false".to_string());
        update_story_in_file(tmp.path(), "27_test", None, None, Some(&fields)).unwrap();

        let result = fs::read_to_string(&filepath).unwrap();
        assert!(result.contains("blocked: false"), "bool should be unquoted: {result}");
        assert!(!result.contains("blocked: \"false\""), "bool must not be quoted: {result}");
    }

    #[test]
    fn update_story_integer_front_matter_written_unquoted() {
        let tmp = tempfile::tempdir().unwrap();
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        let filepath = current.join("28_test.md");
        fs::write(&filepath, "---\nname: T\n---\n\nNo sections.\n").unwrap();

        let mut fields = HashMap::new();
        fields.insert("retry_count".to_string(), "0".to_string());
        update_story_in_file(tmp.path(), "28_test", None, None, Some(&fields)).unwrap();

        let result = fs::read_to_string(&filepath).unwrap();
        assert!(result.contains("retry_count: 0"), "integer should be unquoted: {result}");
        assert!(!result.contains("retry_count: \"0\""), "integer must not be quoted: {result}");
    }

    #[test]
    fn update_story_bool_front_matter_parseable_after_write() {
        let tmp = tempfile::tempdir().unwrap();
        let current = tmp.path().join(".storkit/work/2_current");
        fs::create_dir_all(&current).unwrap();
        let filepath = current.join("29_test.md");
        fs::write(&filepath, "---\nname: My Story\n---\n\nNo sections.\n").unwrap();

        let mut fields = HashMap::new();
        fields.insert("blocked".to_string(), "false".to_string());
        update_story_in_file(tmp.path(), "29_test", None, None, Some(&fields)).unwrap();

        let contents = fs::read_to_string(&filepath).unwrap();
        let meta = parse_front_matter(&contents).expect("front matter should parse");
        assert_eq!(meta.name.as_deref(), Some("My Story"), "name preserved after writing bool field");
    }
}