use comrak::nodes::{AstNode, ListType, NodeValue, TableAlignment};
use comrak::{parse_document, Arena, Options};
use serde_json::{json, Map, Value};

#[derive(Debug, Clone)]
pub struct ParsedLocalMarkdownPage {
    pub title: String,
    pub mnote_id: Option<String>,
    pub body: String,
}

#[derive(Debug, Clone)]
struct MarkdownAstDocument {
    blocks: Vec<MarkdownBlock>,
}

#[derive(Debug, Clone)]
enum MarkdownBlock {
    Paragraph(Vec<MarkdownInline>),
    Heading {
        level: u8,
        content: Vec<MarkdownInline>,
    },
    Quote(Vec<MarkdownInline>),
    CodeBlock {
        language: String,
        text: String,
    },
    Divider,
    BulletListItem(Vec<MarkdownInline>),
    NumberedListItem(Vec<MarkdownInline>),
    Todo {
        checked: bool,
        content: Vec<MarkdownInline>,
    },
    Table {
        alignments: Vec<TableAlignment>,
        rows: Vec<MarkdownTableRow>,
    },
    Media {
        name: String,
        source_path: String,
    },
}

#[derive(Debug, Clone)]
struct MarkdownTableRow {
    is_header: bool,
    cells: Vec<MarkdownTableCell>,
}

#[derive(Debug, Clone)]
struct MarkdownTableCell {
    content: Vec<MarkdownInline>,
}

#[derive(Debug, Clone, PartialEq, Eq)]
struct MarkdownInline {
    text: String,
    styles: MarkdownInlineStyles,
}

#[derive(Debug, Clone, Default, PartialEq, Eq)]
struct MarkdownInlineStyles {
    bold: bool,
    italic: bool,
    strike: bool,
    underline: bool,
    code: bool,
    link: Option<String>,
}

pub fn parse_markdown_page(markdown: &str, file_name: &str) -> ParsedLocalMarkdownPage {
    let (frontmatter, body) = split_frontmatter(markdown);
    let title = frontmatter
        .as_deref()
        .and_then(|content| read_frontmatter_field(content, "title"))
        .or_else(|| extract_first_h1_title(body))
        .unwrap_or_else(|| file_stem_title(file_name));
    let mnote_id = frontmatter
        .as_deref()
        .and_then(|content| read_frontmatter_field(content, "mnote_id"));
    ParsedLocalMarkdownPage {
        title,
        mnote_id,
        body: body.to_string(),
    }
}

pub fn markdown_to_blocks(markdown: &str) -> Value {
    markdown_ast_document_to_blocks(&parse_markdown_ast_document(markdown))
}

pub fn parse_markdown_attachment_link(trimmed: &str) -> Option<(String, String)> {
    let value = trimmed
        .strip_prefix('!')
        .unwrap_or(trimmed)
        .strip_prefix('[')?;
    let (label, rest) = value.split_once("](")?;
    let target = rest.strip_suffix(')')?.trim();
    if target.is_empty()
        || target.starts_with("http://")
        || target.starts_with("https://")
        || target.starts_with('#')
        || target.starts_with("mailto:")
    {
        return None;
    }
    let target_path = std::path::Path::new(target);
    let extension = target_path.extension().and_then(|value| value.to_str())?;
    if extension.eq_ignore_ascii_case("md") || extension.eq_ignore_ascii_case("markdown") {
        return None;
    }
    let fallback_name = target_path
        .file_name()
        .and_then(|value| value.to_str())
        .unwrap_or(target)
        .trim();
    let name = if label.trim().is_empty() {
        fallback_name
    } else {
        label.trim()
    };
    Some((name.to_string(), target.to_string()))
}

fn parse_markdown_ast_document(markdown: &str) -> MarkdownAstDocument {
    let arena = Arena::new();
    let mut options = Options::default();
    options.extension.table = true;
    options.extension.tasklist = true;
    options.extension.strikethrough = true;
    options.extension.autolink = true;
    options.extension.front_matter_delimiter = Some("---".to_string());
    options.parse.tasklist_in_table = true;

    let root = parse_document(&arena, markdown, &options);
    let mut blocks = Vec::new();
    for node in root.children() {
        append_ast_block(node, &mut blocks);
    }
    MarkdownAstDocument { blocks }
}

fn append_ast_block<'a>(node: &'a AstNode<'a>, blocks: &mut Vec<MarkdownBlock>) {
    match node.data.borrow().value.clone() {
        NodeValue::Paragraph => append_ast_paragraph(node, blocks),
        NodeValue::Heading(heading) => blocks.push(MarkdownBlock::Heading {
            level: heading.level,
            content: collect_inline_children(node),
        }),
        NodeValue::BlockQuote => blocks.push(MarkdownBlock::Quote(collect_inline_children(node))),
        NodeValue::ThematicBreak => blocks.push(MarkdownBlock::Divider),
        NodeValue::CodeBlock(code_block) => blocks.push(MarkdownBlock::CodeBlock {
            language: code_block.info.clone(),
            text: code_block.literal.clone(),
        }),
        NodeValue::List(list) => {
            for item in node.children() {
                append_ast_list_item(item, list.list_type == ListType::Ordered, blocks);
            }
        }
        NodeValue::Table(table) => blocks.push(ast_table_to_ir(node, table.alignments)),
        NodeValue::HtmlBlock(html) => blocks.push(MarkdownBlock::Paragraph(vec![MarkdownInline {
            text: html.literal.clone(),
            styles: MarkdownInlineStyles::default(),
        }])),
        NodeValue::FrontMatter(_) => {}
        _ => {
            let text = collect_plain_text(node);
            if !text.is_empty() {
                blocks.push(MarkdownBlock::Paragraph(vec![MarkdownInline {
                    text,
                    styles: MarkdownInlineStyles::default(),
                }]));
            }
        }
    }
}

fn append_ast_paragraph<'a>(node: &'a AstNode<'a>, blocks: &mut Vec<MarkdownBlock>) {
    if let Some((name, source_path)) = paragraph_attachment_media(node) {
        blocks.push(MarkdownBlock::Media { name, source_path });
        return;
    }
    if let Some((name, source_path, remaining)) = paragraph_leading_attachment_media(node) {
        blocks.push(MarkdownBlock::Media { name, source_path });
        let content = merge_adjacent_inline_nodes(remaining);
        if !content.is_empty() {
            blocks.push(MarkdownBlock::Paragraph(content));
        }
        return;
    }
    blocks.push(MarkdownBlock::Paragraph(collect_inline_children(node)));
}

fn append_ast_list_item<'a>(node: &'a AstNode<'a>, ordered: bool, blocks: &mut Vec<MarkdownBlock>) {
    let (is_task, checked) = match node.data.borrow().value.clone() {
        NodeValue::TaskItem(task_item) => (true, task_item.symbol.is_some()),
        NodeValue::Item(_) => (false, false),
        _ => return append_ast_block(node, blocks),
    };
    let mut content = Vec::new();
    for child in node.children() {
        match child.data.borrow().value.clone() {
            NodeValue::Paragraph => content.extend(collect_inline_children(child)),
            _ => append_ast_block(child, blocks),
        }
    }

    if is_task {
        blocks.push(MarkdownBlock::Todo { checked, content });
    } else if ordered {
        blocks.push(MarkdownBlock::NumberedListItem(content));
    } else {
        blocks.push(MarkdownBlock::BulletListItem(content));
    }
}

fn ast_table_to_ir<'a>(node: &'a AstNode<'a>, alignments: Vec<TableAlignment>) -> MarkdownBlock {
    let rows = node
        .children()
        .map(|row| {
            let is_header = matches!(row.data.borrow().value, NodeValue::TableRow(true));
            let cells = row
                .children()
                .map(|cell| MarkdownTableCell {
                    content: collect_inline_children(cell),
                })
                .collect::<Vec<_>>();
            MarkdownTableRow { is_header, cells }
        })
        .collect::<Vec<_>>();
    MarkdownBlock::Table { alignments, rows }
}

fn collect_inline_children<'a>(node: &'a AstNode<'a>) -> Vec<MarkdownInline> {
    let mut nodes = Vec::new();
    for child in node.children() {
        collect_inline_nodes(child, &MarkdownInlineStyles::default(), &mut nodes);
    }
    merge_adjacent_inline_nodes(nodes)
}

fn collect_inline_nodes<'a>(
    node: &'a AstNode<'a>,
    active_styles: &MarkdownInlineStyles,
    nodes: &mut Vec<MarkdownInline>,
) {
    match node.data.borrow().value.clone() {
        NodeValue::Text(text) => push_inline_text_node(nodes, text.as_ref(), active_styles),
        NodeValue::TaskItem(task_item) => {
            let marker = if task_item.symbol.is_some() {
                "[x] "
            } else {
                "[ ] "
            };
            push_inline_text_node(nodes, marker, active_styles);
            for child in node.children() {
                collect_inline_nodes(child, active_styles, nodes);
            }
        }
        NodeValue::Code(code) => {
            let mut styles = active_styles.clone();
            styles.code = true;
            push_inline_text_node(nodes, &code.literal, &styles);
        }
        NodeValue::Strong => {
            let mut styles = active_styles.clone();
            styles.bold = true;
            collect_inline_children_with_styles(node, &styles, nodes);
        }
        NodeValue::Emph => {
            let mut styles = active_styles.clone();
            styles.italic = true;
            collect_inline_children_with_styles(node, &styles, nodes);
        }
        NodeValue::Strikethrough => {
            let mut styles = active_styles.clone();
            styles.strike = true;
            collect_inline_children_with_styles(node, &styles, nodes);
        }
        NodeValue::Underline => {
            let mut styles = active_styles.clone();
            styles.underline = true;
            collect_inline_children_with_styles(node, &styles, nodes);
        }
        NodeValue::Link(link) => {
            let mut styles = active_styles.clone();
            styles.link = Some(link.url.clone());
            collect_inline_children_with_styles(node, &styles, nodes);
        }
        NodeValue::SoftBreak | NodeValue::LineBreak => {
            push_inline_text_node(nodes, " ", active_styles);
        }
        NodeValue::HtmlInline(text) => push_inline_text_node(nodes, text.as_ref(), active_styles),
        NodeValue::Image(link) => {
            let mut styles = active_styles.clone();
            styles.link = Some(link.url.clone());
            push_inline_text_node(nodes, link.url.as_str(), &styles);
        }
        _ => collect_inline_children_with_styles(node, active_styles, nodes),
    }
}

fn collect_inline_children_with_styles<'a>(
    node: &'a AstNode<'a>,
    active_styles: &MarkdownInlineStyles,
    nodes: &mut Vec<MarkdownInline>,
) {
    for child in node.children() {
        collect_inline_nodes(child, active_styles, nodes);
    }
}

fn push_inline_text_node(
    nodes: &mut Vec<MarkdownInline>,
    text: &str,
    styles: &MarkdownInlineStyles,
) {
    if text.is_empty() {
        return;
    }
    nodes.push(MarkdownInline {
        text: text.to_string(),
        styles: styles.clone(),
    });
}

fn merge_adjacent_inline_nodes(nodes: Vec<MarkdownInline>) -> Vec<MarkdownInline> {
    let mut merged = Vec::<MarkdownInline>::new();
    for node in nodes {
        if let Some(last) = merged.last_mut() {
            if last.styles == node.styles {
                last.text.push_str(&node.text);
                continue;
            }
        }
        merged.push(node);
    }
    merged
}

fn paragraph_attachment_media<'a>(node: &'a AstNode<'a>) -> Option<(String, String)> {
    let mut children = node.children();
    let first = children.next()?;
    if children.next().is_some() {
        return None;
    }
    link_attachment_media(first)
}

fn paragraph_leading_attachment_media<'a>(
    node: &'a AstNode<'a>,
) -> Option<(String, String, Vec<MarkdownInline>)> {
    let mut children = node.children();
    let first = children.next()?;
    let (name, source_path) = link_attachment_media(first)?;
    let second = children.next()?;
    if !matches!(
        second.data.borrow().value,
        NodeValue::SoftBreak | NodeValue::LineBreak
    ) {
        return None;
    }
    let mut remaining = Vec::new();
    for child in children {
        collect_inline_nodes(child, &MarkdownInlineStyles::default(), &mut remaining);
    }
    Some((name, source_path, remaining))
}

fn link_attachment_media<'a>(node: &'a AstNode<'a>) -> Option<(String, String)> {
    let NodeValue::Link(link) = &node.data.borrow().value else {
        return None;
    };
    parse_markdown_attachment_link(&format!("[{}]({})", collect_plain_text(node), link.url))
}

fn markdown_ast_document_to_blocks(document: &MarkdownAstDocument) -> Value {
    Value::Array(
        document
            .blocks
            .iter()
            .enumerate()
            .map(|(index, block)| markdown_block_to_json(block, index + 1))
            .collect(),
    )
}

fn markdown_block_to_json(block: &MarkdownBlock, block_number: usize) -> Value {
    match block {
        MarkdownBlock::Paragraph(content) => json_block(
            "paragraph",
            legacy_inline_nodes_to_json(content),
            block_number,
        ),
        MarkdownBlock::Heading { level, content } => json!({
            "id": format!("local-block-{block_number}"),
            "type": "heading",
            "props": { "level": level },
            "content": legacy_inline_nodes_to_json(content),
            "children": [],
        }),
        MarkdownBlock::Quote(content) => {
            json_block("quote", legacy_inline_nodes_to_json(content), block_number)
        }
        MarkdownBlock::CodeBlock { language, text } => json!({
            "id": format!("local-block-{block_number}"),
            "type": "codeBlock",
            "props": { "language": language },
            "content": [{ "type": "text", "text": text, "styles": {} }],
            "children": [],
        }),
        MarkdownBlock::Divider => json!({
            "id": format!("local-block-{block_number}"),
            "type": "divider",
            "content": [],
            "children": [],
        }),
        MarkdownBlock::BulletListItem(content) => json_block(
            "bulletListItem",
            legacy_inline_nodes_to_json(content),
            block_number,
        ),
        MarkdownBlock::NumberedListItem(content) => json_block(
            "numberedListItem",
            legacy_inline_nodes_to_json(content),
            block_number,
        ),
        MarkdownBlock::Todo { checked, content } => json!({
            "id": format!("local-block-{block_number}"),
            "type": "todo",
            "props": { "checked": checked },
            "content": legacy_inline_nodes_to_json(content),
            "children": [],
        }),
        MarkdownBlock::Table { alignments, rows } => {
            table_block_to_json(alignments, rows, block_number)
        }
        MarkdownBlock::Media { name, source_path } => json!({
            "id": format!("local-block-{block_number}"),
            "type": "media",
            "props": {
                "name": name,
                "sourcePath": source_path,
            },
            "content": [],
            "children": [],
        }),
    }
}

fn table_block_to_json(
    alignments: &[TableAlignment],
    rows: &[MarkdownTableRow],
    block_number: usize,
) -> Value {
    let content_rows = rows
        .iter()
        .map(|row| {
            let cells = row
                .cells
                .iter()
                .enumerate()
                .map(|(column_index, cell)| {
                    let cell_type = if row.is_header {
                        "tableHeader"
                    } else {
                        "tableCell"
                    };
                    let text_align = match alignments
                        .get(column_index)
                        .copied()
                        .unwrap_or(TableAlignment::None)
                    {
                        TableAlignment::Left => "left",
                        TableAlignment::Center => "center",
                        TableAlignment::Right => "right",
                        TableAlignment::None => "",
                    };
                    json!({
                        "type": cell_type,
                        "attrs": {
                            "colspan": 1,
                            "rowspan": 1,
                            "colwidth": null,
                            "textAlign": text_align,
                        },
                        "content": [{
                            "type": "paragraph",
                            "content": tiptap_inline_nodes_to_json(&cell.content),
                        }]
                    })
                })
                .collect::<Vec<_>>();
            json!({
                "type": "tableRow",
                "content": cells,
            })
        })
        .collect::<Vec<_>>();
    json!({
        "id": format!("local-block-{block_number}"),
        "type": "table",
        "props": {
            "tiptapTable": {
                "type": "table",
                "attrs": { "blockId": format!("local-block-{block_number}") },
                "content": content_rows,
            }
        },
        "content": [],
        "children": [],
    })
}

fn json_block(block_type: &str, content: Vec<Value>, block_number: usize) -> Value {
    json!({
        "id": format!("local-block-{block_number}"),
        "type": block_type,
        "content": content,
        "children": [],
    })
}

fn legacy_inline_nodes_to_json(nodes: &[MarkdownInline]) -> Vec<Value> {
    nodes
        .iter()
        .map(|node| {
            json!({
                "type": "text",
                "text": node.text,
                "styles": legacy_styles_to_json(&node.styles),
            })
        })
        .collect()
}

fn legacy_styles_to_json(styles: &MarkdownInlineStyles) -> Value {
    let mut object = Map::new();
    if styles.bold {
        object.insert("bold".to_string(), Value::Bool(true));
    }
    if styles.italic {
        object.insert("italic".to_string(), Value::Bool(true));
    }
    if styles.strike {
        object.insert("strike".to_string(), Value::Bool(true));
    }
    if styles.underline {
        object.insert("underline".to_string(), Value::Bool(true));
    }
    if styles.code {
        object.insert("code".to_string(), Value::Bool(true));
    }
    if let Some(href) = styles
        .link
        .as_deref()
        .map(str::trim)
        .filter(|href| !href.is_empty())
    {
        object.insert("link".to_string(), Value::String(href.to_string()));
    }
    Value::Object(object)
}

fn tiptap_inline_nodes_to_json(nodes: &[MarkdownInline]) -> Vec<Value> {
    nodes
        .iter()
        .filter(|node| !node.text.is_empty())
        .map(|node| {
            let mut object = Map::new();
            object.insert("type".to_string(), Value::String("text".to_string()));
            object.insert("text".to_string(), Value::String(node.text.clone()));
            let marks = tiptap_marks_from_styles(&node.styles);
            if !marks.is_empty() {
                object.insert("marks".to_string(), Value::Array(marks));
            }
            Value::Object(object)
        })
        .collect()
}

fn tiptap_marks_from_styles(styles: &MarkdownInlineStyles) -> Vec<Value> {
    let mut marks = Vec::new();
    if styles.bold {
        marks.push(json!({ "type": "bold" }));
    }
    if styles.italic {
        marks.push(json!({ "type": "italic" }));
    }
    if styles.underline {
        marks.push(json!({ "type": "underline" }));
    }
    if styles.strike {
        marks.push(json!({ "type": "strike" }));
    }
    if styles.code {
        marks.push(json!({ "type": "code" }));
    }
    if let Some(href) = styles
        .link
        .as_deref()
        .map(str::trim)
        .filter(|href| !href.is_empty())
    {
        marks.push(json!({ "type": "link", "attrs": { "href": href } }));
    }
    marks
}

fn collect_plain_text<'a>(node: &'a AstNode<'a>) -> String {
    let mut parts = Vec::new();
    for descendant in node.descendants() {
        if let NodeValue::Text(text) = &descendant.data.borrow().value {
            parts.push(text.as_ref().to_string());
        }
    }
    parts.join("")
}

pub(crate) fn split_frontmatter(markdown: &str) -> (Option<String>, &str) {
    let normalized = markdown.strip_prefix('\u{feff}').unwrap_or(markdown);
    if !normalized.starts_with("---\n") {
        return (None, normalized);
    }
    let rest = &normalized[4..];
    if let Some(end) = rest.find("\n---\n") {
        let frontmatter = rest[..end].to_string();
        let body = &rest[end + 5..];
        return (Some(frontmatter), body);
    }
    (None, normalized)
}

fn read_frontmatter_field(frontmatter: &str, key: &str) -> Option<String> {
    frontmatter.lines().find_map(|line| {
        let (candidate_key, value) = line.split_once(':')?;
        if candidate_key.trim() != key {
            return None;
        }
        let trimmed = value.trim().trim_matches('"').trim_matches('\'').trim();
        if trimmed.is_empty() {
            None
        } else {
            Some(trimmed.to_string())
        }
    })
}

fn extract_first_h1_title(body: &str) -> Option<String> {
    body.lines().find_map(|line| {
        let trimmed = line.trim();
        trimmed
            .strip_prefix("# ")
            .map(str::trim)
            .filter(|value| !value.is_empty())
            .map(ToOwned::to_owned)
    })
}

pub(crate) fn file_stem_title(file_name: &str) -> String {
    std::path::Path::new(file_name)
        .file_stem()
        .and_then(|stem| stem.to_str())
        .map(str::trim)
        .filter(|value| !value.is_empty())
        .unwrap_or(file_name)
        .to_string()
}