use ai::{
    embedding::{Embedding, EmbeddingProvider},
    models::TruncationDirection,
};
use anyhow::{anyhow, Result};
use language::{Grammar, Language};
use rusqlite::{
    types::{FromSql, FromSqlResult, ToSqlOutput, ValueRef},
    ToSql,
};
use sha1::{Digest, Sha1};
use std::{
    borrow::Cow,
    cmp::{self, Reverse},
    collections::HashSet,
    ops::Range,
    path::Path,
    sync::Arc,
};
use tree_sitter::{Parser, QueryCursor};

#[derive(Debug, PartialEq, Eq, Clone, Hash)]
pub struct SpanDigest(pub [u8; 20]);

impl FromSql for SpanDigest {
    fn column_result(value: ValueRef) -> FromSqlResult<Self> {
        let blob = value.as_blob()?;
        let bytes =
            blob.try_into()
                .map_err(|_| rusqlite::types::FromSqlError::InvalidBlobSize {
                    expected_size: 20,
                    blob_size: blob.len(),
                })?;
        return Ok(SpanDigest(bytes));
    }
}

impl ToSql for SpanDigest {
    fn to_sql(&self) -> rusqlite::Result<ToSqlOutput> {
        self.0.to_sql()
    }
}

impl From<&'_ str> for SpanDigest {
    fn from(value: &'_ str) -> Self {
        let mut sha1 = Sha1::new();
        sha1.update(value);
        Self(sha1.finalize().into())
    }
}

#[derive(Debug, PartialEq, Clone)]
pub struct Span {
    pub name: String,
    pub range: Range<usize>,
    pub content: String,
    pub embedding: Option<Embedding>,
    pub digest: SpanDigest,
    pub token_count: usize,
}

const CODE_CONTEXT_TEMPLATE: &str =
    "The below code snippet is from file '<path>'\n\n```<language>\n<item>\n```";
const ENTIRE_FILE_TEMPLATE: &str =
    "The below snippet is from file '<path>'\n\n```<language>\n<item>\n```";
const MARKDOWN_CONTEXT_TEMPLATE: &str = "The below file contents is from file '<path>'\n\n<item>";
pub const PARSEABLE_ENTIRE_FILE_TYPES: &[&str] = &[
    "TOML", "YAML", "CSS", "HEEX", "ERB", "SVELTE", "HTML", "Scheme",
];

pub struct CodeContextRetriever {
    pub parser: Parser,
    pub cursor: QueryCursor,
    pub embedding_provider: Arc<dyn EmbeddingProvider>,
}

// Every match has an item, this represents the fundamental treesitter symbol and anchors the search
// Every match has one or more 'name' captures. These indicate the display range of the item for deduplication.
// If there are preceding comments, we track this with a context capture
// If there is a piece that should be collapsed in hierarchical queries, we capture it with a collapse capture
// If there is a piece that should be kept inside a collapsed node, we capture it with a keep capture
#[derive(Debug, Clone)]
pub struct CodeContextMatch {
    pub start_col: usize,
    pub item_range: Option<Range<usize>>,
    pub name_range: Option<Range<usize>>,
    pub context_ranges: Vec<Range<usize>>,
    pub collapse_ranges: Vec<Range<usize>>,
}

impl CodeContextRetriever {
    pub fn new(embedding_provider: Arc<dyn EmbeddingProvider>) -> Self {
        Self {
            parser: Parser::new(),
            cursor: QueryCursor::new(),
            embedding_provider,
        }
    }

    fn parse_entire_file(
        &self,
        relative_path: Option<&Path>,
        language_name: Arc<str>,
        content: &str,
    ) -> Result<Vec<Span>> {
        let document_span = ENTIRE_FILE_TEMPLATE
            .replace(
                "<path>",
                &relative_path.map_or(Cow::Borrowed("untitled"), |path| path.to_string_lossy()),
            )
            .replace("<language>", language_name.as_ref())
            .replace("<item>", &content);
        let digest = SpanDigest::from(document_span.as_str());
        let model = self.embedding_provider.base_model();
        let document_span = model.truncate(
            &document_span,
            model.capacity()?,
            ai::models::TruncationDirection::End,
        )?;
        let token_count = model.count_tokens(&document_span)?;

        Ok(vec![Span {
            range: 0..content.len(),
            content: document_span,
            embedding: Default::default(),
            name: language_name.to_string(),
            digest,
            token_count,
        }])
    }

    fn parse_markdown_file(
        &self,
        relative_path: Option<&Path>,
        content: &str,
    ) -> Result<Vec<Span>> {
        let document_span = MARKDOWN_CONTEXT_TEMPLATE
            .replace(
                "<path>",
                &relative_path.map_or(Cow::Borrowed("untitled"), |path| path.to_string_lossy()),
            )
            .replace("<item>", &content);
        let digest = SpanDigest::from(document_span.as_str());

        let model = self.embedding_provider.base_model();
        let document_span = model.truncate(
            &document_span,
            model.capacity()?,
            ai::models::TruncationDirection::End,
        )?;
        let token_count = model.count_tokens(&document_span)?;

        Ok(vec![Span {
            range: 0..content.len(),
            content: document_span,
            embedding: None,
            name: "Markdown".to_string(),
            digest,
            token_count,
        }])
    }

    fn get_matches_in_file(
        &mut self,
        content: &str,
        grammar: &Arc<Grammar>,
    ) -> Result<Vec<CodeContextMatch>> {
        let embedding_config = grammar
            .embedding_config
            .as_ref()
            .ok_or_else(|| anyhow!("no embedding queries"))?;
        self.parser.set_language(&grammar.ts_language).unwrap();

        let tree = self
            .parser
            .parse(&content, None)
            .ok_or_else(|| anyhow!("parsing failed"))?;

        let mut captures: Vec<CodeContextMatch> = Vec::new();
        let mut collapse_ranges: Vec<Range<usize>> = Vec::new();
        let mut keep_ranges: Vec<Range<usize>> = Vec::new();
        for mat in self.cursor.matches(
            &embedding_config.query,
            tree.root_node(),
            content.as_bytes(),
        ) {
            let mut start_col = 0;
            let mut item_range: Option<Range<usize>> = None;
            let mut name_range: Option<Range<usize>> = None;
            let mut context_ranges: Vec<Range<usize>> = Vec::new();
            collapse_ranges.clear();
            keep_ranges.clear();
            for capture in mat.captures {
                if capture.index == embedding_config.item_capture_ix {
                    item_range = Some(capture.node.byte_range());
                    start_col = capture.node.start_position().column;
                } else if Some(capture.index) == embedding_config.name_capture_ix {
                    name_range = Some(capture.node.byte_range());
                } else if Some(capture.index) == embedding_config.context_capture_ix {
                    context_ranges.push(capture.node.byte_range());
                } else if Some(capture.index) == embedding_config.collapse_capture_ix {
                    collapse_ranges.push(capture.node.byte_range());
                } else if Some(capture.index) == embedding_config.keep_capture_ix {
                    keep_ranges.push(capture.node.byte_range());
                }
            }

            captures.push(CodeContextMatch {
                start_col,
                item_range,
                name_range,
                context_ranges,
                collapse_ranges: subtract_ranges(&collapse_ranges, &keep_ranges),
            });
        }
        Ok(captures)
    }

    pub fn parse_file_with_template(
        &mut self,
        relative_path: Option<&Path>,
        content: &str,
        language: Arc<Language>,
    ) -> Result<Vec<Span>> {
        let language_name = language.name();

        if PARSEABLE_ENTIRE_FILE_TYPES.contains(&language_name.as_ref()) {
            return self.parse_entire_file(relative_path, language_name, &content);
        } else if ["Markdown", "Plain Text"].contains(&language_name.as_ref()) {
            return self.parse_markdown_file(relative_path, &content);
        }

        let mut spans = self.parse_file(content, language)?;
        for span in &mut spans {
            let document_content = CODE_CONTEXT_TEMPLATE
                .replace(
                    "<path>",
                    &relative_path.map_or(Cow::Borrowed("untitled"), |path| path.to_string_lossy()),
                )
                .replace("<language>", language_name.as_ref())
                .replace("item", &span.content);

            let model = self.embedding_provider.base_model();
            let document_content = model.truncate(
                &document_content,
                model.capacity()?,
                TruncationDirection::End,
            )?;
            let token_count = model.count_tokens(&document_content)?;

            span.content = document_content;
            span.token_count = token_count;
        }
        Ok(spans)
    }

    pub fn parse_file(&mut self, content: &str, language: Arc<Language>) -> Result<Vec<Span>> {
        let grammar = language
            .grammar()
            .ok_or_else(|| anyhow!("no grammar for language"))?;

        // Iterate through query matches
        let matches = self.get_matches_in_file(content, grammar)?;

        let language_scope = language.default_scope();
        let placeholder = language_scope.collapsed_placeholder();

        let mut spans = Vec::new();
        let mut collapsed_ranges_within = Vec::new();
        let mut parsed_name_ranges = HashSet::new();
        for (i, context_match) in matches.iter().enumerate() {
            // Items which are collapsible but not embeddable have no item range
            let item_range = if let Some(item_range) = context_match.item_range.clone() {
                item_range
            } else {
                continue;
            };

            // Checks for deduplication
            let name;
            if let Some(name_range) = context_match.name_range.clone() {
                name = content
                    .get(name_range.clone())
                    .map_or(String::new(), |s| s.to_string());
                if parsed_name_ranges.contains(&name_range) {
                    continue;
                }
                parsed_name_ranges.insert(name_range);
            } else {
                name = String::new();
            }

            collapsed_ranges_within.clear();
            'outer: for remaining_match in &matches[(i + 1)..] {
                for collapsed_range in &remaining_match.collapse_ranges {
                    if item_range.start <= collapsed_range.start
                        && item_range.end >= collapsed_range.end
                    {
                        collapsed_ranges_within.push(collapsed_range.clone());
                    } else {
                        break 'outer;
                    }
                }
            }

            collapsed_ranges_within.sort_by_key(|r| (r.start, Reverse(r.end)));

            let mut span_content = String::new();
            for context_range in &context_match.context_ranges {
                add_content_from_range(
                    &mut span_content,
                    content,
                    context_range.clone(),
                    context_match.start_col,
                );
                span_content.push_str("\n");
            }

            let mut offset = item_range.start;
            for collapsed_range in &collapsed_ranges_within {
                if collapsed_range.start > offset {
                    add_content_from_range(
                        &mut span_content,
                        content,
                        offset..collapsed_range.start,
                        context_match.start_col,
                    );
                    offset = collapsed_range.start;
                }

                if collapsed_range.end > offset {
                    span_content.push_str(placeholder);
                    offset = collapsed_range.end;
                }
            }

            if offset < item_range.end {
                add_content_from_range(
                    &mut span_content,
                    content,
                    offset..item_range.end,
                    context_match.start_col,
                );
            }

            let sha1 = SpanDigest::from(span_content.as_str());
            spans.push(Span {
                name,
                content: span_content,
                range: item_range.clone(),
                embedding: None,
                digest: sha1,
                token_count: 0,
            })
        }

        return Ok(spans);
    }
}

pub(crate) fn subtract_ranges(
    ranges: &[Range<usize>],
    ranges_to_subtract: &[Range<usize>],
) -> Vec<Range<usize>> {
    let mut result = Vec::new();

    let mut ranges_to_subtract = ranges_to_subtract.iter().peekable();

    for range in ranges {
        let mut offset = range.start;

        while offset < range.end {
            if let Some(range_to_subtract) = ranges_to_subtract.peek() {
                if offset < range_to_subtract.start {
                    let next_offset = cmp::min(range_to_subtract.start, range.end);
                    result.push(offset..next_offset);
                    offset = next_offset;
                } else {
                    let next_offset = cmp::min(range_to_subtract.end, range.end);
                    offset = next_offset;
                }

                if offset >= range_to_subtract.end {
                    ranges_to_subtract.next();
                }
            } else {
                result.push(offset..range.end);
                offset = range.end;
            }
        }
    }

    result
}

fn add_content_from_range(
    output: &mut String,
    content: &str,
    range: Range<usize>,
    start_col: usize,
) {
    for mut line in content.get(range.clone()).unwrap_or("").lines() {
        for _ in 0..start_col {
            if line.starts_with(' ') {
                line = &line[1..];
            } else {
                break;
            }
        }
        output.push_str(line);
        output.push('\n');
    }
    output.pop();
}