//! Utility helpers shared across the `DeepSeek` CLI.

use std::fs;
use std::path::Path;

use crate::models::{ContentBlock, Message};
use anyhow::{Context, Result};
use ignore::WalkBuilder;
use serde_json::Value;

// === Project Mapping Helpers ===

/// Identify if a file is a "key" file for project identification.
#[must_use]
pub fn is_key_file(path: &Path) -> bool {
    let Some(file_name) = path.file_name().and_then(|n| n.to_str()) else {
        return false;
    };

    matches!(
        file_name.to_lowercase().as_str(),
        "cargo.toml"
            | "package.json"
            | "requirements.txt"
            | "build.gradle"
            | "pom.xml"
            | "readme.md"
            | "agents.md"
            | "claude.md"
            | "makefile"
            | "dockerfile"
            | "main.rs"
            | "lib.rs"
            | "index.js"
            | "index.ts"
            | "app.py"
    )
}

/// Generate a high-level summary of the project based on key files.
#[must_use]
pub fn summarize_project(root: &Path) -> String {
    let mut key_files = Vec::new();

    let mut builder = WalkBuilder::new(root);
    builder.hidden(false).follow_links(true).max_depth(Some(2));
    let walker = builder.build();

    for entry in walker {
        let entry = match entry {
            Ok(entry) => entry,
            Err(_) => continue,
        };
        if is_key_file(entry.path())
            && let Ok(rel) = entry.path().strip_prefix(root)
        {
            key_files.push(rel.to_string_lossy().to_string());
        }
    }

    if key_files.is_empty() {
        return "Unknown project type".to_string();
    }

    let mut types = Vec::new();
    if key_files
        .iter()
        .any(|f| f.to_lowercase().contains("cargo.toml"))
    {
        types.push("Rust");
    }
    if key_files
        .iter()
        .any(|f| f.to_lowercase().contains("package.json"))
    {
        types.push("JavaScript/Node.js");
    }
    if key_files
        .iter()
        .any(|f| f.to_lowercase().contains("requirements.txt"))
    {
        types.push("Python");
    }

    if types.is_empty() {
        format!("Project with key files: {}", key_files.join(", "))
    } else {
        format!("A {} project", types.join(" and "))
    }
}

/// Generate a tree-like view of the project structure.
#[must_use]
pub fn project_tree(root: &Path, max_depth: usize) -> String {
    let mut tree_lines = Vec::new();

    let mut builder = WalkBuilder::new(root);
    builder
        .hidden(false)
        .follow_links(true)
        .max_depth(Some(max_depth + 1));
    let walker = builder.build();

    for entry in walker {
        let entry = match entry {
            Ok(entry) => entry,
            Err(_) => continue,
        };

        let path = entry.path();
        let depth = entry.depth();

        if depth == 0 || depth > max_depth {
            continue;
        }

        let rel_path = path.strip_prefix(root).unwrap_or(path);
        let indent = "  ".repeat(depth - 1);
        let prefix = if entry.file_type().is_some_and(|ft| ft.is_dir()) {
            "DIR: "
        } else {
            "FILE: "
        };

        tree_lines.push(format!(
            "{}{}{}",
            indent,
            prefix,
            rel_path.file_name().unwrap_or_default().to_string_lossy()
        ));
    }

    tree_lines.join("\n")
}

// === Filesystem Helpers ===

#[allow(dead_code)]
pub fn ensure_dir(path: &Path) -> Result<()> {
    fs::create_dir_all(path)
        .with_context(|| format!("Failed to create directory: {}", path.display()))
}

/// Render JSON with pretty formatting, falling back to a compact string on error.
#[must_use]
#[allow(dead_code)]
pub fn pretty_json(value: &Value) -> String {
    serde_json::to_string_pretty(value).unwrap_or_else(|_| value.to_string())
}

/// Truncate a string to a maximum length, adding an ellipsis if truncated.
///
/// Uses char boundaries to avoid panicking on multi-byte UTF-8 characters.
#[must_use]
pub fn truncate_with_ellipsis(s: &str, max_len: usize, ellipsis: &str) -> String {
    if s.len() <= max_len {
        return s.to_string();
    }
    let budget = max_len.saturating_sub(ellipsis.len());
    // Find the last char boundary that fits within the byte budget.
    let safe_end = s
        .char_indices()
        .map(|(i, _)| i)
        .take_while(|&i| i <= budget)
        .last()
        .unwrap_or(0);
    format!("{}{}", &s[..safe_end], ellipsis)
}

/// Percent-encode a string for use in URL query parameters.
///
/// Encodes all characters except unreserved characters (A-Z, a-z, 0-9, `-`, `_`, `.`, `~`).
/// Spaces are encoded as `+`.
#[must_use]
pub fn url_encode(input: &str) -> String {
    let mut encoded = String::new();
    for ch in input.bytes() {
        match ch {
            b'A'..=b'Z' | b'a'..=b'z' | b'0'..=b'9' | b'-' | b'_' | b'.' | b'~' => {
                encoded.push(ch as char)
            }
            b' ' => encoded.push('+'),
            _ => encoded.push_str(&format!("%{ch:02X}")),
        }
    }
    encoded
}

/// Estimate the total character count across message content blocks.
#[must_use]
pub fn estimate_message_chars(messages: &[Message]) -> usize {
    let mut total = 0;
    for msg in messages {
        for block in &msg.content {
            match block {
                ContentBlock::Text { text, .. } => total += text.len(),
                ContentBlock::Thinking { thinking } => total += thinking.len(),
                ContentBlock::ToolUse { input, .. } => total += input.to_string().len(),
                ContentBlock::ToolResult { content, .. } => total += content.len(),
                ContentBlock::ServerToolUse { .. }
                | ContentBlock::ToolSearchToolResult { .. }
                | ContentBlock::CodeExecutionToolResult { .. } => {}
            }
        }
    }
    total
}
