//! Markdown file–backed `MemoryRepository`.
//! Each memory is stored as a `.md` file with YAML-ish frontmatter.

use std::collections::HashMap;
use std::io::Write;
use std::path::Path;

use zesdex_domain::cms::{Memory, MemoryRepository, RepositoryError};

/// File-based `MemoryRepository` that stores memories as `.md` files with
/// YAML-ish frontmatter.
#[derive(Debug, Clone, Default)]
pub struct MarkdownMemoryRepository;

impl MarkdownMemoryRepository {
    pub fn new() -> Self {
        Self
    }

    /// Escape newlines in field values so they do not break the
    /// line-oriented frontmatter parser.
    fn escape_newlines(s: &str) -> String {
        s.replace('\n', "\\n")
    }

    /// Unescape `\n` back to actual newlines after frontmatter parsing.
    fn unescape_newlines(s: &str) -> String {
        s.replace("\\n", "\n")
    }

    fn build_frontmatter(memory: &Memory) -> String {
        let outcome_line = memory
            .outcome
            .as_ref()
            .map(|o| format!("outcome: {}\n", Self::escape_newlines(o)))
            .unwrap_or_default();
        let scope_line = memory
            .scope
            .as_ref()
            .map(|s| format!("scope: {}\n", Self::escape_newlines(s)))
            .unwrap_or_default();
        let before_line = memory
            .before_snippet
            .as_ref()
            .map(|s| format!("before: {}\n", Self::escape_newlines(s)))
            .unwrap_or_default();
        let after_line = memory
            .after_snippet
            .as_ref()
            .map(|s| format!("after: {}\n", Self::escape_newlines(s)))
            .unwrap_or_default();
        let prov_line = if memory.provenances.is_empty() {
            String::new()
        } else {
            format!("provenances: {}\n", memory.provenances.join(", "))
        };
        format!(
            "name: {name}\ndescription: {desc}\nkind: {kind}\n\
             created_at: {created}\nupdated_at: {updated}\nlifecycle: {lifecycle}\n\
             {outcome}{scope}{before}{after}{prov}",
            name = memory.name,
            desc = memory.description,
            kind = memory.kind,
            created = memory.created_at,
            updated = memory.updated_at,
            lifecycle = memory.lifecycle,
            outcome = outcome_line,
            scope = scope_line,
            before = before_line,
            after = after_line,
            prov = prov_line,
        )
    }

    fn parse_frontmatter(front: &str) -> HashMap<String, String> {
        front
            .lines()
            .filter_map(|l| {
                let mut it = l.splitn(2, ':');
                Some((
                    it.next()?.trim().to_string(),
                    it.next()?.trim().to_string(),
                ))
            })
            .collect()
    }

    fn parse(content: &str) -> std::io::Result<Memory> {
        let content = content.strip_prefix("---\n").unwrap_or(content);
        let parts: Vec<&str> = content.splitn(2, "\n---\n").collect();
        if parts.len() < 2 {
            return Err(std::io::Error::new(
                std::io::ErrorKind::InvalidData,
                "missing frontmatter",
            ));
        }
        let front = Self::parse_frontmatter(parts[0]);
        let body = parts.get(1).unwrap_or(&"").trim().to_string();
        Ok(Memory {
            name: front.get("name").cloned().unwrap_or_default(),
            description: front.get("description").cloned().unwrap_or_default(),
            content: body,
            kind: front
                .get("kind")
                .cloned()
                .unwrap_or_else(|| "reference".to_string()),
            created_at: front
                .get("created_at")
                .and_then(|v| v.parse().ok())
                .unwrap_or(0),
            updated_at: front
                .get("updated_at")
                .and_then(|v| v.parse().ok())
                .unwrap_or(0),
            outcome: front
                .get("outcome")
                .cloned()
                .filter(|s| !s.is_empty())
                .map(|s| Self::unescape_newlines(&s)),
            lifecycle: front
                .get("lifecycle")
                .cloned()
                .unwrap_or_else(|| "new".to_string()),
            scope: front
                .get("scope")
                .cloned()
                .filter(|s| !s.is_empty())
                .map(|s| Self::unescape_newlines(&s)),
            before_snippet: front
                .get("before")
                .cloned()
                .filter(|s| !s.is_empty())
                .map(|s| Self::unescape_newlines(&s)),
            after_snippet: front
                .get("after")
                .cloned()
                .filter(|s| !s.is_empty())
                .map(|s| Self::unescape_newlines(&s)),
            provenances: front
                .get("provenances")
                .cloned()
                .map(|s| s.split(", ").map(String::from).collect())
                .unwrap_or_default(),
        })
    }
}

impl MemoryRepository for MarkdownMemoryRepository {
    fn list(&self, memory_dir: &Path) -> Result<Vec<String>, RepositoryError> {
        let Ok(entries) = std::fs::read_dir(memory_dir) else {
            return Ok(Vec::new());
        };
        let slugs: Vec<String> = entries
            .filter_map(std::result::Result::ok)
            .filter(|e| e.path().extension().is_some_and(|x| x == "md"))
            .filter_map(|e| {
                let name = e.file_name().to_string_lossy().to_string();
                if name == "MEMORY.md" {
                    return None;
                }
                name.strip_suffix(".md")
                    .map(std::string::ToString::to_string)
            })
            .collect();
        Ok(slugs)
    }

    fn load(&self, memory_dir: &Path, name: &str) -> Result<Memory, RepositoryError> {
        let path = Memory::path(memory_dir, name);
        let content = std::fs::read_to_string(&path)?;
        let memory = Self::parse(&content)
            .map_err(|e| RepositoryError::Other(format!("failed to parse memory '{name}': {e}")))?;
        Ok(memory)
    }

    fn save(&self, memory_dir: &Path, memory: &Memory) -> Result<(), RepositoryError> {
        let path = Memory::path(memory_dir, &memory.name);
        let parent = path.parent().unwrap();
        std::fs::create_dir_all(parent)?;

        let frontmatter = Self::build_frontmatter(memory);
        let content = format!("---\n{frontmatter}---\n\n{}", memory.content);

        let tmp = parent.join(format!(".{}.tmp", uuid::Uuid::new_v4()));
        {
            let mut f = std::fs::OpenOptions::new()
                .create(true)
                .truncate(true)
                .write(true)
                .open(&tmp)?;
            f.write_all(content.as_bytes())?;
            f.sync_all()?;
        }
        std::fs::rename(&tmp, &path)?;
        if let Some(p) = path.parent() {
            if let Ok(d) = std::fs::File::open(p) {
                let _ = d.sync_all();
            }
        }
        Ok(())
    }

    fn delete(&self, memory_dir: &Path, name: &str) -> Result<(), RepositoryError> {
        let path = Memory::path(memory_dir, name);
        if path.exists() {
            std::fs::remove_file(&path)?;
        }
        Ok(())
    }
}