use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::path::{Path, PathBuf};
use std::fs;
use anyhow::{Result, Context, bail};

use crate::version::ANVIL_VERSION;

pub const CONFIG_FILENAME: &str = ".anvil.toml";

#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct ProjectConfig {
    pub project: ProjectMeta,
    pub build: BuildConfig,
    pub monitor: MonitorConfig,
    #[serde(default)]
    pub boards: HashMap<String, BoardProfile>,
    #[serde(default, skip_serializing_if = "HashMap::is_empty")]
    pub pins: HashMap<String, BoardPinConfig>,
}

#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct ProjectMeta {
    pub name: String,
    pub anvil_version: String,
}

#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct BuildConfig {
    /// Name of the default board from [boards.*]
    #[serde(default)]
    pub default: String,
    pub warnings: String,
    pub include_dirs: Vec<String>,
    pub extra_flags: Vec<String>,
    /// Legacy: FQBN used to live here directly. Now lives in [boards.*].
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub fqbn: Option<String>,
}

#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct MonitorConfig {
    pub baud: u32,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub port: Option<String>,
}

/// A named board with its FQBN and optional baud override.
#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct BoardProfile {
    pub fqbn: String,
    #[serde(default, skip_serializing_if = "Option::is_none")]
    pub baud: Option<u32>,
}

/// Pin configuration for a specific board.
#[derive(Debug, Serialize, Deserialize, Clone, Default)]
pub struct BoardPinConfig {
    /// Individual pin assignments: name -> { pin, mode }
    #[serde(default, skip_serializing_if = "HashMap::is_empty")]
    pub assignments: HashMap<String, PinAssignment>,
    /// Bus group reservations: "spi" -> { cs = 10 }, "i2c" -> {}
    #[serde(default, skip_serializing_if = "HashMap::is_empty")]
    pub buses: HashMap<String, BusConfig>,
}

/// A single pin assignment with a friendly name.
#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct PinAssignment {
    pub pin: u8,
    pub mode: String,
}

/// Configuration for a claimed bus group.
/// User-selectable pins (like CS for SPI) are stored as flattened keys.
#[derive(Debug, Serialize, Deserialize, Clone, Default)]
pub struct BusConfig {
    #[serde(flatten)]
    pub user_pins: HashMap<String, u8>,
}

impl ProjectConfig {
    /// Create a new project config with sensible defaults.
    pub fn new(name: &str) -> Self {
        let mut boards = HashMap::new();
        boards.insert("uno".to_string(), BoardProfile {
            fqbn: "arduino:avr:uno".to_string(),
            baud: None,
        });
        Self {
            project: ProjectMeta {
                name: name.to_string(),
                anvil_version: ANVIL_VERSION.to_string(),
            },
            build: BuildConfig {
                default: "uno".to_string(),
                fqbn: None,
                warnings: "more".to_string(),
                include_dirs: vec!["lib/hal".to_string(), "lib/app".to_string()],
                extra_flags: vec!["-Werror".to_string()],
            },
            monitor: MonitorConfig {
                baud: 115200,
                port: None,
            },
            boards,
            pins: HashMap::new(),
        }
    }

    /// Create a new project config with a specific board preset.
    pub fn new_with_board(name: &str, board_name: &str, fqbn: &str, baud: u32) -> Self {
        let mut config = Self::new(name);
        config.build.default = board_name.to_string();
        config.boards.clear();
        config.boards.insert(board_name.to_string(), BoardProfile {
            fqbn: fqbn.to_string(),
            baud: None,
        });
        config.monitor.baud = baud;
        config
    }

    /// Get the default board's FQBN and baud.
    pub fn default_board(&self) -> Result<(String, u32)> {
        self.resolve_board(&self.build.default)
    }

    /// Get the default board's FQBN.
    pub fn default_fqbn(&self) -> Result<String> {
        let (fqbn, _) = self.default_board()?;
        Ok(fqbn)
    }

    /// Resolve the FQBN and baud for a named board.
    /// Returns (fqbn, baud).
    pub fn resolve_board(&self, board_name: &str) -> Result<(String, u32)> {
        match self.boards.get(board_name) {
            Some(profile) => {
                let baud = profile.baud.unwrap_or(self.monitor.baud);
                Ok((profile.fqbn.clone(), baud))
            }
            None => {
                let available: Vec<&String> = self.boards.keys().collect();
                if available.is_empty() {
                    bail!(
                        "No board '{}' found in .anvil.toml.\n  \
                         No boards are defined. Add one: anvil board --add {}",
                        board_name, board_name
                    );
                } else {
                    bail!(
                        "No board '{}' found in .anvil.toml.\n  \
                         Available: {}\n  \
                         Add it: anvil board --add {}",
                        board_name,
                        available.iter().map(|s| s.as_str()).collect::<Vec<_>>().join(", "),
                        board_name
                    );
                }
            }
        }
    }

    /// Load config from a project directory.
    pub fn load(project_root: &Path) -> Result<Self> {
        let config_path = project_root.join(CONFIG_FILENAME);
        if !config_path.exists() {
            bail!(
                "Not an Anvil project (missing {}).\n\
                 Create one with: anvil new <name>",
                CONFIG_FILENAME
            );
        }
        let contents = fs::read_to_string(&config_path)
            .context(format!("Failed to read {}", config_path.display()))?;
        let mut config: ProjectConfig = toml::from_str(&contents)
            .context(format!("Failed to parse {}", config_path.display()))?;

        // Migrate old format: fqbn in [build] -> [boards.X] + default
        if config.build.default.is_empty() {
            if let Some(ref legacy_fqbn) = config.build.fqbn {
                let board_name = crate::board::presets::PRESETS.iter()
                    .find(|p| p.fqbn == *legacy_fqbn)
                    .map(|p| p.name.to_string())
                    .unwrap_or_else(|| "default".to_string());

                // Text-based migration of the actual file
                migrate_config_file(&config_path, &board_name, legacy_fqbn)?;

                // Update in-memory config to match
                let fqbn_clone = legacy_fqbn.clone();
                config.build.fqbn = None;
                config.build.default = board_name.clone();
                config.boards.entry(board_name).or_insert(BoardProfile {
                    fqbn: fqbn_clone,
                    baud: None,
                });
            }
        }

        Ok(config)
    }

    /// Save config to a project directory.
    pub fn save(&self, project_root: &Path) -> Result<()> {
        let config_path = project_root.join(CONFIG_FILENAME);
        let contents = toml::to_string_pretty(self)
            .context("Failed to serialize config")?;
        fs::write(&config_path, contents)
            .context(format!("Failed to write {}", config_path.display()))?;
        Ok(())
    }

    /// Walk up from a directory to find the project root containing .anvil.toml.
    pub fn find_project_root(start: &Path) -> Result<PathBuf> {
        let mut dir = if start.is_absolute() {
            start.to_path_buf()
        } else {
            std::env::current_dir()?.join(start)
        };

        for _ in 0..10 {
            if dir.join(CONFIG_FILENAME).exists() {
                return Ok(dir);
            }
            match dir.parent() {
                Some(parent) => dir = parent.to_path_buf(),
                None => break,
            }
        }

        bail!(
            "No {} found in {} or any parent directory.\n\
             Create a project with: anvil new <name>",
            CONFIG_FILENAME,
            start.display()
        );
    }

    /// Resolve include directories to absolute paths relative to project root.
    pub fn resolve_include_flags(&self, project_root: &Path) -> Vec<String> {
        let mut flags = Vec::new();
        for dir in &self.build.include_dirs {
            let abs = project_root.join(dir);
            if abs.is_dir() {
                flags.push(format!("-I{}", abs.display()));
            }
        }
        flags
    }

    /// Build the full extra_flags string for arduino-cli.
    pub fn extra_flags_string(&self, project_root: &Path) -> String {
        let mut parts = self.resolve_include_flags(project_root);
        for flag in &self.build.extra_flags {
            parts.push(flag.clone());
        }
        parts.join(" ")
    }
}

impl Default for ProjectConfig {
    fn default() -> Self {
        Self::new("untitled")
    }
}

/// Return the Anvil home directory (~/.anvil).
pub fn anvil_home() -> Result<PathBuf> {
    let home = dirs::home_dir()
        .context("Could not determine home directory")?;
    let anvil_dir = home.join(".anvil");
    fs::create_dir_all(&anvil_dir)?;
    Ok(anvil_dir)
}

// -- Text-based .anvil.toml editing -----------------------------------------
// These operate on the raw file text to preserve comments and formatting.

/// Migrate an old-format config: add default = "X" to [build] and add
/// [boards.X] section if needed. Keeps old fqbn line for backward
/// compatibility with scripts that haven't been refreshed yet.
fn migrate_config_file(config_path: &Path, board_name: &str, fqbn: &str) -> Result<()> {
    let content = fs::read_to_string(config_path)
        .context("Failed to read .anvil.toml for migration")?;

    let mut output = String::new();
    let mut in_build = false;
    let mut added_default = false;
    let mut has_board_section = false;

    // Check if [boards.NAME] already exists
    let section_header = format!("[boards.{}]", board_name);
    for line in content.lines() {
        if line.trim() == section_header {
            has_board_section = true;
            break;
        }
    }

    for line in content.lines() {
        let trimmed = line.trim();

        // Track which section we're in
        if trimmed == "[build]" {
            in_build = true;
            output.push_str(line);
            output.push('\n');
            continue;
        }
        if trimmed.starts_with('[') && trimmed != "[build]" {
            // Leaving [build] -- add default before leaving if we haven't yet
            if in_build && !added_default {
                output.push_str(&format!("default = \"{}\"\n", board_name));
                added_default = true;
            }
            in_build = false;
        }

        // In [build]: add default right before fqbn (natural reading order)
        if in_build && !added_default && trimmed.starts_with("fqbn") && trimmed.contains('=') {
            output.push_str(&format!("default = \"{}\"\n", board_name));
            added_default = true;
        }

        output.push_str(line);
        output.push('\n');
    }

    // Add [boards.NAME] section if it doesn't already exist
    if !has_board_section {
        while output.ends_with("\n\n") {
            output.pop();
        }
        output.push('\n');
        output.push_str(&format!("\n[boards.{}]\n", board_name));
        output.push_str(&format!("fqbn = \"{}\"\n", fqbn));
    }

    fs::write(config_path, &output)
        .context("Failed to write migrated .anvil.toml")?;

    eprintln!(
        "\x1b[33minfo\x1b[0m  Migrated .anvil.toml: default = \"{}\"{}",
        board_name,
        if has_board_section { "" } else { ", added [boards] section" }
    );
    eprintln!(
        "\x1b[33minfo\x1b[0m  Run \x1b[36manvil refresh --force\x1b[0m to update scripts."
    );

    Ok(())
}

/// Set or change the default board in .anvil.toml (text-based edit).
/// Returns the old default name (empty string if there wasn't one).
pub fn set_default_in_file(config_path: &Path, board_name: &str) -> Result<String> {
    let content = fs::read_to_string(config_path)
        .context("Failed to read .anvil.toml")?;

    let mut output = String::new();
    let mut in_build = false;
    let mut replaced = false;
    let mut old_default = String::new();

    for line in content.lines() {
        let trimmed = line.trim();

        if trimmed == "[build]" {
            in_build = true;
            output.push_str(line);
            output.push('\n');
            continue;
        }
        if trimmed.starts_with('[') && trimmed != "[build]" {
            // Leaving [build] without having found default -- add it
            if in_build && !replaced {
                output.push_str(&format!("default = \"{}\"\n", board_name));
                replaced = true;
            }
            in_build = false;
        }

        if in_build && trimmed.starts_with("default") && trimmed.contains('=') {
            // Extract old value
            if let Some(val) = trimmed.split('=').nth(1) {
                old_default = val.trim().trim_matches('"').to_string();
            }
            output.push_str(&format!("default = \"{}\"\n", board_name));
            replaced = true;
            continue;
        }

        output.push_str(line);
        output.push('\n');
    }

    // Edge case: [build] was the last section and had no default
    if in_build && !replaced {
        output.push_str(&format!("default = \"{}\"\n", board_name));
    }

    fs::write(config_path, &output)
        .context("Failed to write .anvil.toml")?;

    Ok(old_default)
}

#[cfg(test)]
mod tests {
    use super::*;
    use tempfile::TempDir;

    #[test]
    fn test_new_config_defaults() {
        let config = ProjectConfig::new("test_project");
        assert_eq!(config.project.name, "test_project");
        assert_eq!(config.build.default, "uno");
        assert_eq!(config.monitor.baud, 115200);
        assert!(config.build.include_dirs.contains(&"lib/hal".to_string()));
        assert!(config.boards.contains_key("uno"));
        assert_eq!(config.boards["uno"].fqbn, "arduino:avr:uno");
    }

    #[test]
    fn test_save_and_load() {
        let tmp = TempDir::new().unwrap();
        let config = ProjectConfig::new("roundtrip");
        config.save(tmp.path()).unwrap();

        let loaded = ProjectConfig::load(tmp.path()).unwrap();
        assert_eq!(loaded.project.name, "roundtrip");
        assert_eq!(loaded.build.default, "uno");
        assert_eq!(loaded.monitor.baud, config.monitor.baud);
        assert!(loaded.boards.contains_key("uno"));
    }

    #[test]
    fn test_new_with_board() {
        let config = ProjectConfig::new_with_board(
            "test", "mega", "arduino:avr:mega:cpu=atmega2560", 115200
        );
        assert_eq!(config.build.default, "mega");
        assert!(config.boards.contains_key("mega"));
        assert_eq!(config.boards["mega"].fqbn, "arduino:avr:mega:cpu=atmega2560");
        assert!(!config.boards.contains_key("uno"));
    }

    #[test]
    fn test_find_project_root() {
        let tmp = TempDir::new().unwrap();
        let config = ProjectConfig::new("finder");
        config.save(tmp.path()).unwrap();

        let sub = tmp.path().join("sketch").join("deep");
        fs::create_dir_all(&sub).unwrap();

        let found = ProjectConfig::find_project_root(&sub).unwrap();
        assert_eq!(found, tmp.path());
    }

    #[test]
    fn test_find_project_root_not_found() {
        let tmp = TempDir::new().unwrap();
        let result = ProjectConfig::find_project_root(tmp.path());
        assert!(result.is_err());
    }

    #[test]
    fn test_resolve_include_flags() {
        let tmp = TempDir::new().unwrap();
        fs::create_dir_all(tmp.path().join("lib/hal")).unwrap();
        fs::create_dir_all(tmp.path().join("lib/app")).unwrap();

        let config = ProjectConfig::new("includes");
        let flags = config.resolve_include_flags(tmp.path());

        assert_eq!(flags.len(), 2);
        assert!(flags[0].starts_with("-I"));
        assert!(flags[0].contains("lib"));
    }

    #[test]
    fn test_extra_flags_string() {
        let tmp = TempDir::new().unwrap();
        fs::create_dir_all(tmp.path().join("lib/hal")).unwrap();
        fs::create_dir_all(tmp.path().join("lib/app")).unwrap();

        let config = ProjectConfig::new("flags");
        let flags = config.extra_flags_string(tmp.path());

        assert!(flags.contains("-Werror"));
        assert!(flags.contains("-I"));
    }

    #[test]
    fn test_default_board() {
        let config = ProjectConfig::new("test");
        let (fqbn, baud) = config.default_board().unwrap();
        assert_eq!(fqbn, "arduino:avr:uno");
        assert_eq!(baud, 115200);
    }

    #[test]
    fn test_resolve_board_named() {
        let mut config = ProjectConfig::new("test");
        config.boards.insert("mega".to_string(), BoardProfile {
            fqbn: "arduino:avr:mega:cpu=atmega2560".to_string(),
            baud: Some(9600),
        });

        let (fqbn, baud) = config.resolve_board("mega").unwrap();
        assert_eq!(fqbn, "arduino:avr:mega:cpu=atmega2560");
        assert_eq!(baud, 9600);
    }

    #[test]
    fn test_resolve_board_inherits_baud() {
        let mut config = ProjectConfig::new("test");
        config.boards.insert("nano".to_string(), BoardProfile {
            fqbn: "arduino:avr:nano:cpu=atmega328".to_string(),
            baud: None,
        });

        let (fqbn, baud) = config.resolve_board("nano").unwrap();
        assert_eq!(fqbn, "arduino:avr:nano:cpu=atmega328");
        assert_eq!(baud, 115200);
    }

    #[test]
    fn test_resolve_board_unknown() {
        let config = ProjectConfig::new("test");
        assert!(config.resolve_board("esp32").is_err());
    }

    #[test]
    fn test_board_roundtrip() {
        let tmp = TempDir::new().unwrap();
        let mut config = ProjectConfig::new("multi");
        config.boards.insert("mega".to_string(), BoardProfile {
            fqbn: "arduino:avr:mega:cpu=atmega2560".to_string(),
            baud: Some(57600),
        });
        config.save(tmp.path()).unwrap();

        let loaded = ProjectConfig::load(tmp.path()).unwrap();
        assert!(loaded.boards.contains_key("mega"));
        let mega = &loaded.boards["mega"];
        assert_eq!(mega.fqbn, "arduino:avr:mega:cpu=atmega2560");
        assert_eq!(mega.baud, Some(57600));
    }

    #[test]
    fn test_migrate_old_format() {
        let tmp = TempDir::new().unwrap();
        let old_config = r#"[project]
name = "hand"
anvil_version = "1.0.0"

[build]
fqbn = "arduino:avr:uno"
warnings = "more"
include_dirs = ["lib/hal", "lib/app"]
extra_flags = ["-Werror"]

[monitor]
baud = 115200

[boards.micro]
fqbn = "arduino:avr:micro"
"#;
        fs::write(tmp.path().join(CONFIG_FILENAME), old_config).unwrap();

        let config = ProjectConfig::load(tmp.path()).unwrap();
        assert_eq!(config.build.default, "uno");
        assert!(config.boards.contains_key("uno"));
        assert_eq!(config.boards["uno"].fqbn, "arduino:avr:uno");
        assert!(config.boards.contains_key("micro"));

        // Verify the file was rewritten
        let content = fs::read_to_string(tmp.path().join(CONFIG_FILENAME)).unwrap();
        assert!(content.contains("default = \"uno\""));
        assert!(content.contains("[boards.uno]"));
        // Old fqbn stays in [build] for backward compat with old scripts
        assert!(content.contains("fqbn = \"arduino:avr:uno\""));
    }

    #[test]
    fn test_migrate_preserves_existing_boards() {
        let tmp = TempDir::new().unwrap();
        let old_config = r#"[project]
name = "test"
anvil_version = "1.0.0"

[build]
fqbn = "arduino:avr:mega:cpu=atmega2560"
warnings = "more"
include_dirs = ["lib/hal", "lib/app"]
extra_flags = ["-Werror"]

[monitor]
baud = 115200
"#;
        fs::write(tmp.path().join(CONFIG_FILENAME), old_config).unwrap();

        let config = ProjectConfig::load(tmp.path()).unwrap();
        assert_eq!(config.build.default, "mega");
        assert!(config.boards.contains_key("mega"));
    }

    #[test]
    fn test_set_default_in_file() {
        let tmp = TempDir::new().unwrap();
        let config = ProjectConfig::new("test");
        config.save(tmp.path()).unwrap();

        let config_path = tmp.path().join(CONFIG_FILENAME);
        let old = set_default_in_file(&config_path, "mega").unwrap();
        assert_eq!(old, "uno");

        let content = fs::read_to_string(&config_path).unwrap();
        assert!(content.contains("default = \"mega\""));
        assert!(!content.contains("default = \"uno\""));
    }

    #[test]
    fn test_set_default_adds_when_missing() {
        let tmp = TempDir::new().unwrap();
        let content = r#"[project]
name = "test"
anvil_version = "1.0.0"

[build]
warnings = "more"
include_dirs = ["lib/hal", "lib/app"]
extra_flags = ["-Werror"]

[monitor]
baud = 115200

[boards.uno]
fqbn = "arduino:avr:uno"
"#;
        let config_path = tmp.path().join(CONFIG_FILENAME);
        fs::write(&config_path, content).unwrap();

        let old = set_default_in_file(&config_path, "uno").unwrap();
        assert_eq!(old, "");

        let result = fs::read_to_string(&config_path).unwrap();
        assert!(result.contains("default = \"uno\""));
    }
}