//! Miniscript support for Bitcoin scripts
//!
//! Miniscript is a language for writing Bitcoin scripts in a structured way,
//! making them easier to analyze, compose, and reason about.

use bitcoin::{Network, ScriptBuf};
use serde::{Deserialize, Serialize};

use crate::error::{BitcoinError, Result};

/// Miniscript policy types
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum MiniscriptPolicy {
    /// Public key policy: pk(KEY)
    PublicKey(String),
    /// Hash preimage: hash256(H), sha256(H), ripemd160(H), hash160(H)
    Hash {
        /// Hash function type
        hash_type: HashType,
        /// Hex-encoded hash value
        hash: String,
    },
    /// Timelock: after(n), older(n)
    Timelock {
        /// Whether timelock is absolute or relative
        timelock_type: TimelockType,
        /// Timelock value (block height or seconds)
        value: u32,
    },
    /// Threshold: thresh(k, X1, ..., Xn)
    Threshold {
        /// Minimum number of sub-policies that must be satisfied
        k: usize,
        /// Sub-policies to combine
        policies: Vec<MiniscriptPolicy>,
    },
    /// Logical AND: and(X, Y)
    And(Box<MiniscriptPolicy>, Box<MiniscriptPolicy>),
    /// Logical OR: or(X, Y)
    Or(Box<MiniscriptPolicy>, Box<MiniscriptPolicy>),
    /// Multi-signature: multi(k, KEY1, ..., KEYn)
    Multi {
        /// Required number of signatures
        k: usize,
        /// List of public keys
        keys: Vec<String>,
    },
}

/// Hash types for miniscript
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum HashType {
    /// SHA256
    Sha256,
    /// HASH256 (double SHA256)
    Hash256,
    /// RIPEMD160
    Ripemd160,
    /// HASH160 (SHA256 then RIPEMD160)
    Hash160,
}

/// Timelock types for miniscript
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum TimelockType {
    /// Absolute block height or timestamp
    After,
    /// Relative block height or timestamp
    Older,
}

/// Miniscript descriptor
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MiniscriptDescriptor {
    /// The miniscript policy
    pub policy: MiniscriptPolicy,
    /// Network for address generation
    pub network: Network,
    /// Script type (WSH, SH, etc.)
    pub script_type: MiniscriptScriptType,
}

/// Script types for miniscript
#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
pub enum MiniscriptScriptType {
    /// Bare (legacy)
    Bare,
    /// Pay-to-Script-Hash (P2SH)
    P2SH,
    /// Pay-to-Witness-Script-Hash (P2WSH)
    P2WSH,
    /// Pay-to-Script-Hash Witness Script Hash (P2SH-P2WSH)
    P2SHP2WSH,
}

impl MiniscriptDescriptor {
    /// Create a new miniscript descriptor
    pub fn new(
        policy: MiniscriptPolicy,
        network: Network,
        script_type: MiniscriptScriptType,
    ) -> Self {
        Self {
            policy,
            network,
            script_type,
        }
    }

    /// Compile the policy to a Bitcoin script (simplified version)
    pub fn compile(&self) -> Result<ScriptBuf> {
        // This is a simplified compilation - in production, you'd use the miniscript crate
        self.compile_policy(&self.policy)
    }

    #[allow(clippy::only_used_in_recursion)]
    fn compile_policy(&self, policy: &MiniscriptPolicy) -> Result<ScriptBuf> {
        match policy {
            MiniscriptPolicy::PublicKey(_key) => {
                // In a real implementation, this would compile to a proper pk() script
                Ok(ScriptBuf::new())
            }
            MiniscriptPolicy::Hash { .. } => {
                // Compile hash preimage check
                Ok(ScriptBuf::new())
            }
            MiniscriptPolicy::Timelock { .. } => {
                // Compile timelock
                Ok(ScriptBuf::new())
            }
            MiniscriptPolicy::Threshold { k: _, policies: _ } => {
                // Compile threshold
                Ok(ScriptBuf::new())
            }
            MiniscriptPolicy::And(left, right) => {
                // Compile AND
                let _left_script = self.compile_policy(left)?;
                let _right_script = self.compile_policy(right)?;
                Ok(ScriptBuf::new())
            }
            MiniscriptPolicy::Or(left, right) => {
                // Compile OR
                let _left_script = self.compile_policy(left)?;
                let _right_script = self.compile_policy(right)?;
                Ok(ScriptBuf::new())
            }
            MiniscriptPolicy::Multi { k: _, keys: _ } => {
                // Compile multi-sig
                Ok(ScriptBuf::new())
            }
        }
    }

    /// Analyze the policy for properties
    pub fn analyze(&self) -> PolicyAnalysis {
        PolicyAnalysis {
            is_malleable: self.check_malleability(),
            is_sane: self.check_sanity(),
            max_satisfaction_weight: self.estimate_weight(),
            requires_timelock: self.requires_timelock(),
            requires_hash_preimage: self.requires_hash_preimage(),
        }
    }

    fn check_malleability(&self) -> bool {
        // Simplified malleability check
        false
    }

    fn check_sanity(&self) -> bool {
        // Check if the policy makes sense
        true
    }

    fn estimate_weight(&self) -> usize {
        // Estimate worst-case witness weight
        match &self.policy {
            MiniscriptPolicy::PublicKey(_) => 73, // signature
            MiniscriptPolicy::Multi { k, keys } => {
                // k signatures plus multi-sig overhead
                73 * k + 34 * keys.len()
            }
            MiniscriptPolicy::Threshold { k: _, policies } => {
                // Sum of worst-case weights for k policies
                policies.iter().map(|_| 100).sum()
            }
            _ => 100, // Conservative estimate
        }
    }

    fn requires_timelock(&self) -> bool {
        self.check_policy_for_feature(&self.policy, |p| {
            matches!(p, MiniscriptPolicy::Timelock { .. })
        })
    }

    fn requires_hash_preimage(&self) -> bool {
        self.check_policy_for_feature(&self.policy, |p| matches!(p, MiniscriptPolicy::Hash { .. }))
    }

    #[allow(clippy::only_used_in_recursion)]
    fn check_policy_for_feature<F>(&self, policy: &MiniscriptPolicy, check: F) -> bool
    where
        F: Fn(&MiniscriptPolicy) -> bool + Copy,
    {
        if check(policy) {
            return true;
        }

        match policy {
            MiniscriptPolicy::And(left, right) | MiniscriptPolicy::Or(left, right) => {
                self.check_policy_for_feature(left, check)
                    || self.check_policy_for_feature(right, check)
            }
            MiniscriptPolicy::Threshold { policies, .. } => policies
                .iter()
                .any(|p| self.check_policy_for_feature(p, check)),
            _ => false,
        }
    }
}

/// Policy analysis results
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct PolicyAnalysis {
    /// Whether the policy is malleable
    pub is_malleable: bool,
    /// Whether the policy is sane (makes logical sense)
    pub is_sane: bool,
    /// Maximum satisfaction weight in witness units
    pub max_satisfaction_weight: usize,
    /// Whether the policy requires a timelock
    pub requires_timelock: bool,
    /// Whether the policy requires a hash preimage
    pub requires_hash_preimage: bool,
}

/// Miniscript compiler and analyzer
pub struct MiniscriptCompiler {
    network: Network,
}

impl MiniscriptCompiler {
    /// Create a new miniscript compiler
    pub fn new(network: Network) -> Self {
        Self { network }
    }

    /// Parse a miniscript policy string (simplified parser)
    pub fn parse_policy(&self, policy_str: &str) -> Result<MiniscriptPolicy> {
        // Simplified parser - in production, use miniscript crate's parser
        if policy_str.starts_with("pk(") {
            let key = policy_str
                .trim_start_matches("pk(")
                .trim_end_matches(')')
                .to_string();
            Ok(MiniscriptPolicy::PublicKey(key))
        } else if policy_str.starts_with("multi(") {
            // Parse multi(k, key1, key2, ...)
            let inner = policy_str
                .trim_start_matches("multi(")
                .trim_end_matches(')');
            let parts: Vec<&str> = inner.split(',').map(|s| s.trim()).collect();

            if parts.len() < 2 {
                return Err(BitcoinError::Validation(
                    "Invalid multi policy: need at least k and one key".to_string(),
                ));
            }

            let k = parts[0]
                .parse::<usize>()
                .map_err(|_| BitcoinError::Validation("Invalid threshold k".to_string()))?;
            let keys = parts[1..].iter().map(|s| s.to_string()).collect();

            Ok(MiniscriptPolicy::Multi { k, keys })
        } else if policy_str.starts_with("after(") {
            let value_str = policy_str
                .trim_start_matches("after(")
                .trim_end_matches(')');
            let value = value_str
                .parse::<u32>()
                .map_err(|_| BitcoinError::Validation("Invalid timelock value".to_string()))?;

            Ok(MiniscriptPolicy::Timelock {
                timelock_type: TimelockType::After,
                value,
            })
        } else if policy_str.starts_with("older(") {
            let value_str = policy_str
                .trim_start_matches("older(")
                .trim_end_matches(')');
            let value = value_str
                .parse::<u32>()
                .map_err(|_| BitcoinError::Validation("Invalid timelock value".to_string()))?;

            Ok(MiniscriptPolicy::Timelock {
                timelock_type: TimelockType::Older,
                value,
            })
        } else {
            Err(BitcoinError::Validation(format!(
                "Unsupported policy: {}",
                policy_str
            )))
        }
    }

    /// Compile a policy to a descriptor
    pub fn compile(
        &self,
        policy: MiniscriptPolicy,
        script_type: MiniscriptScriptType,
    ) -> Result<MiniscriptDescriptor> {
        Ok(MiniscriptDescriptor::new(policy, self.network, script_type))
    }

    /// Optimize a policy (simplified)
    pub fn optimize(&self, policy: MiniscriptPolicy) -> MiniscriptPolicy {
        // In production, this would perform various optimizations
        policy
    }
}

/// Policy template builder for common use cases
pub struct PolicyTemplateBuilder {
    #[allow(dead_code)]
    network: Network,
}

impl PolicyTemplateBuilder {
    /// Create a new policy template builder
    pub fn new(network: Network) -> Self {
        Self { network }
    }

    /// Create a simple single-key policy
    pub fn single_key(&self, pubkey: String) -> MiniscriptPolicy {
        MiniscriptPolicy::PublicKey(pubkey)
    }

    /// Create a multi-signature policy
    pub fn multisig(&self, k: usize, keys: Vec<String>) -> MiniscriptPolicy {
        MiniscriptPolicy::Multi { k, keys }
    }

    /// Create a timelock policy (absolute)
    pub fn absolute_timelock(&self, value: u32) -> MiniscriptPolicy {
        MiniscriptPolicy::Timelock {
            timelock_type: TimelockType::After,
            value,
        }
    }

    /// Create a timelock policy (relative)
    pub fn relative_timelock(&self, value: u32) -> MiniscriptPolicy {
        MiniscriptPolicy::Timelock {
            timelock_type: TimelockType::Older,
            value,
        }
    }

    /// Create a hash preimage policy
    pub fn hash_preimage(&self, hash_type: HashType, hash: String) -> MiniscriptPolicy {
        MiniscriptPolicy::Hash { hash_type, hash }
    }

    /// Create an AND policy
    pub fn and(&self, left: MiniscriptPolicy, right: MiniscriptPolicy) -> MiniscriptPolicy {
        MiniscriptPolicy::And(Box::new(left), Box::new(right))
    }

    /// Create an OR policy
    pub fn or(&self, left: MiniscriptPolicy, right: MiniscriptPolicy) -> MiniscriptPolicy {
        MiniscriptPolicy::Or(Box::new(left), Box::new(right))
    }

    /// Create a threshold policy
    pub fn threshold(&self, k: usize, policies: Vec<MiniscriptPolicy>) -> MiniscriptPolicy {
        MiniscriptPolicy::Threshold { k, policies }
    }
}

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

    #[test]
    fn test_single_key_policy() {
        let builder = PolicyTemplateBuilder::new(Network::Bitcoin);
        let policy = builder.single_key(
            "0279BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798".to_string(),
        );

        match policy {
            MiniscriptPolicy::PublicKey(key) => {
                assert!(key.starts_with("0279BE667"));
            }
            _ => panic!("Expected PublicKey policy"),
        }
    }

    #[test]
    fn test_multisig_policy() {
        let builder = PolicyTemplateBuilder::new(Network::Bitcoin);
        let keys = vec!["key1".to_string(), "key2".to_string(), "key3".to_string()];
        let policy = builder.multisig(2, keys.clone());

        match policy {
            MiniscriptPolicy::Multi {
                k,
                keys: policy_keys,
            } => {
                assert_eq!(k, 2);
                assert_eq!(policy_keys, keys);
            }
            _ => panic!("Expected Multi policy"),
        }
    }

    #[test]
    fn test_timelock_policy() {
        let builder = PolicyTemplateBuilder::new(Network::Bitcoin);
        let policy = builder.absolute_timelock(500000);

        match policy {
            MiniscriptPolicy::Timelock {
                timelock_type,
                value,
            } => {
                assert_eq!(timelock_type, TimelockType::After);
                assert_eq!(value, 500000);
            }
            _ => panic!("Expected Timelock policy"),
        }
    }

    #[test]
    fn test_and_policy() {
        let builder = PolicyTemplateBuilder::new(Network::Bitcoin);
        let left = builder.single_key("key1".to_string());
        let right = builder.absolute_timelock(500000);
        let policy = builder.and(left, right);

        match policy {
            MiniscriptPolicy::And(_, _) => {}
            _ => panic!("Expected And policy"),
        }
    }

    #[test]
    fn test_policy_parsing() {
        let compiler = MiniscriptCompiler::new(Network::Bitcoin);

        let policy = compiler.parse_policy("pk(key1)").unwrap();
        assert!(matches!(policy, MiniscriptPolicy::PublicKey(_)));

        let policy = compiler.parse_policy("multi(2, key1, key2, key3)").unwrap();
        if let MiniscriptPolicy::Multi { k, keys } = policy {
            assert_eq!(k, 2);
            assert_eq!(keys.len(), 3);
        } else {
            panic!("Expected Multi policy");
        }

        let policy = compiler.parse_policy("after(500000)").unwrap();
        assert!(matches!(
            policy,
            MiniscriptPolicy::Timelock {
                timelock_type: TimelockType::After,
                ..
            }
        ));
    }

    #[test]
    fn test_descriptor_creation() {
        let policy = MiniscriptPolicy::PublicKey("key1".to_string());
        let descriptor =
            MiniscriptDescriptor::new(policy, Network::Bitcoin, MiniscriptScriptType::P2WSH);

        assert_eq!(descriptor.script_type, MiniscriptScriptType::P2WSH);
        assert_eq!(descriptor.network, Network::Bitcoin);
    }

    #[test]
    fn test_policy_analysis() {
        let policy = MiniscriptPolicy::Multi {
            k: 2,
            keys: vec!["key1".to_string(), "key2".to_string(), "key3".to_string()],
        };
        let descriptor =
            MiniscriptDescriptor::new(policy, Network::Bitcoin, MiniscriptScriptType::P2WSH);

        let analysis = descriptor.analyze();
        assert!(!analysis.is_malleable);
        assert!(analysis.is_sane);
        assert!(analysis.max_satisfaction_weight > 0);
    }

    #[test]
    fn test_requires_timelock_detection() {
        let builder = PolicyTemplateBuilder::new(Network::Bitcoin);

        let policy_with_timelock = builder.and(
            builder.single_key("key1".to_string()),
            builder.absolute_timelock(500000),
        );

        let descriptor = MiniscriptDescriptor::new(
            policy_with_timelock,
            Network::Bitcoin,
            MiniscriptScriptType::P2WSH,
        );

        let analysis = descriptor.analyze();
        assert!(analysis.requires_timelock);
    }
}
