//! Semantic validation for Storybook entities
//!
//! This module validates semantic constraints that can't be checked during
//! parsing:
//! - Reserved keyword conflicts in field names
//! - Trait value ranges
//! - Schedule time overlaps
//! - Life arc transition validity
//! - Behavior tree action registry checks
//! - Relationship bond values (0.0 .. 1.0)

use std::collections::HashSet;

use crate::{
    resolve::{
        ErrorCollector,
        ResolveError,
        Result,
    },
    syntax::ast::*,
};

/// List of reserved keywords that cannot be used as field names
const RESERVED_KEYWORDS: &[&str] = &[
    // Top-level declaration keywords
    "character",
    "template",
    "life_arc",
    "schedule",
    "behavior",
    "institution",
    "relationship",
    "location",
    "species",
    "enum",
    // Statement keywords
    "use",
    "state",
    "on",
    "as",
    "remove",
    "append",
    "strict",
    "include",
    "from",
    // Expression keywords
    "self",
    "other",
    "forall",
    "exists",
    "in",
    "where",
    "and",
    "or",
    "not",
    "is",
    "true",
    "false",
];

/// Validate that field names don't conflict with reserved keywords
pub fn validate_no_reserved_keywords(fields: &[Field], collector: &mut ErrorCollector) {
    for field in fields {
        if RESERVED_KEYWORDS.contains(&field.name.as_str()) {
            collector.add(ResolveError::ValidationError {
                message: format!(
                    "Field name '{}' is a reserved keyword and cannot be used",
                    field.name
                ),
                help: Some(format!(
                    "The name '{}' is reserved by the Storybook language. Try using a different name like '{}Type', '{}Value', or 'my{}'.",
                    field.name,
                    field.name,
                    field.name,
                    field.name.chars().next().unwrap_or('x').to_uppercase().collect::<String>() + &field.name[1..]
                )),
            });
        }
    }
}

/// Validate trait values are within valid ranges
pub fn validate_trait_ranges(fields: &[Field], collector: &mut ErrorCollector) {
    for field in fields {
        match &field.value {
            | Value::Decimal(f) => {
                // Normalized trait values should be 0.0 .. 1.0
                if (field.name.ends_with("_normalized") ||
                    field.name == "bond" ||
                    field.name == "trust" ||
                    field.name == "love") &&
                    !(0.0..=1.0).contains(f)
                {
                    collector.add(ResolveError::TraitOutOfRange {
                        field: field.name.clone(),
                        value: f.to_string(),
                        min: 0.0,
                        max: 1.0,
                    });
                }
            },
            | Value::Number(i) => {
                // Age should be reasonable
                if field.name == "age" && (*i < 0 || *i > 150) {
                    collector.add(ResolveError::TraitOutOfRange {
                        field: "age".to_string(),
                        value: i.to_string(),
                        min: 0.0,
                        max: 150.0,
                    });
                }
            },
            | _ => {},
        }
    }
}

/// Validate relationship bond values are in [0.0, 1.0]
pub fn validate_relationship_bonds(relationships: &[Relationship], collector: &mut ErrorCollector) {
    for rel in relationships {
        for field in &rel.fields {
            if field.name == "bond" {
                if let Value::Decimal(f) = field.value {
                    if !(0.0..=1.0).contains(&f) {
                        collector.add(ResolveError::TraitOutOfRange {
                            field: "bond".to_string(),
                            value: f.to_string(),
                            min: 0.0,
                            max: 1.0,
                        });
                    }
                }
            }
        }

        // Validate participant fields
        for participant in &rel.participants {
            validate_trait_ranges(&participant.fields, collector);
        }
    }
}

/// Validate schedule blocks don't overlap in time
pub fn validate_schedule_overlaps(schedule: &Schedule, collector: &mut ErrorCollector) {
    // Sort blocks by start time
    let mut sorted_blocks: Vec<_> = schedule.blocks.iter().collect();
    sorted_blocks.sort_by_key(|b| (b.start.hour as u32) * 60 + (b.start.minute as u32));

    // Check for overlaps
    for i in 0..sorted_blocks.len() {
        for j in (i + 1)..sorted_blocks.len() {
            let block1 = sorted_blocks[i];
            let block2 = sorted_blocks[j];

            let end1 = (block1.end.hour as u32) * 60 + (block1.end.minute as u32);
            let start2 = (block2.start.hour as u32) * 60 + (block2.start.minute as u32);

            // Check if blocks overlap
            if end1 > start2 {
                collector.add(ResolveError::ScheduleOverlap {
                    block1: format!(
                        "{} ({}:{:02}-{}:{:02})",
                        block1.name.as_ref().unwrap_or(&block1.activity),
                        block1.start.hour,
                        block1.start.minute,
                        block1.end.hour,
                        block1.end.minute
                    ),
                    block2: format!(
                        "{} ({}:{:02}-{}:{:02})",
                        block2.name.as_ref().unwrap_or(&block2.activity),
                        block2.start.hour,
                        block2.start.minute,
                        block2.end.hour,
                        block2.end.minute
                    ),
                    end1: format!("{}:{:02}", block1.end.hour, block1.end.minute),
                    start2: format!("{}:{:02}", block2.start.hour, block2.start.minute),
                });
            }
        }
    }
}

/// Validate life arc state machine has valid transitions
pub fn validate_life_arc_transitions(life_arc: &LifeArc, collector: &mut ErrorCollector) {
    // Collect all state names
    let mut state_names = HashSet::new();
    for state in &life_arc.states {
        state_names.insert(state.name.clone());
    }

    // Validate all transitions point to valid states
    for state in &life_arc.states {
        for transition in &state.transitions {
            if !state_names.contains(&transition.to) {
                let available_states = state_names
                    .iter()
                    .map(|s| format!("'{}'", s))
                    .collect::<Vec<_>>()
                    .join(", ");

                collector.add(ResolveError::UnknownLifeArcState {
                    life_arc: life_arc.name.clone(),
                    state: state.name.clone(),
                    target: transition.to.clone(),
                    available_states,
                });
            }
        }
    }

    // Warn if states have no outgoing transitions (terminal states)
    // This is not an error, just informational
}

/// Validate behavior tree actions are known
///
/// If action_registry is empty, skips validation (no schema provided).
pub fn validate_behavior_tree_actions(
    tree: &Behavior,
    action_registry: &HashSet<String>,
    collector: &mut ErrorCollector,
) {
    // Skip validation if no action schema was provided
    if action_registry.is_empty() {
        return;
    }

    validate_tree_node_actions(&tree.root, action_registry, &tree.name, collector)
}

fn validate_tree_node_actions(
    node: &BehaviorNode,
    action_registry: &HashSet<String>,
    tree_name: &str,
    collector: &mut ErrorCollector,
) {
    match node {
        | BehaviorNode::Sequence { children, .. } | BehaviorNode::Selector { children, .. } => {
            for child in children {
                validate_tree_node_actions(child, action_registry, tree_name, collector);
            }
        },
        | BehaviorNode::Action(name, _params) => {
            if !action_registry.contains(name) {
                collector.add(ResolveError::UnknownBehaviorAction {
                    tree: tree_name.to_string(),
                    action: name.clone(),
                });
            }
        },
        | BehaviorNode::Condition(_) => {
            // Conditions are validated separately via expression validation
        },
        | BehaviorNode::Decorator { child, .. } => {
            validate_tree_node_actions(child, action_registry, tree_name, collector);
        },
        | BehaviorNode::SubTree(_path) => {
            // SubTree references validated separately
        },
    }
}

/// Validate character resource linking
///
/// Checks:
/// 1. No duplicate behavior tree references
/// 2. Priority values are valid (handled by type system)
pub fn validate_character_resource_links(character: &Character, collector: &mut ErrorCollector) {
    // Check for duplicate behavior tree references
    if let Some(ref behavior_links) = character.uses_behaviors {
        let mut seen_trees: HashSet<String> = HashSet::new();

        for link in behavior_links {
            let tree_name = link.tree.join("::");

            if seen_trees.contains(&tree_name) {
                collector.add(ResolveError::ValidationError {
                    message: format!(
                        "Character '{}' has duplicate behavior tree reference: {}",
                        character.name,
                        tree_name
                    ),
                    help: Some(format!(
                        "The behavior tree '{}' is referenced multiple times in the uses behaviors list. Each behavior tree should only be referenced once. If you want different conditions or priorities, combine them into a single entry.",
                        tree_name
                    )),
                });
            }

            seen_trees.insert(tree_name);
        }
    }

    // Check for duplicate schedule references
    if let Some(ref schedules) = character.uses_schedule {
        let mut seen_schedules: HashSet<String> = HashSet::new();

        for schedule in schedules {
            if seen_schedules.contains(schedule) {
                collector.add(ResolveError::ValidationError {
                    message: format!(
                        "Character '{}' has duplicate schedule reference: {}",
                        character.name,
                        schedule
                    ),
                    help: Some(format!(
                        "The schedule '{}' is referenced multiple times. Each schedule should only be referenced once.",
                        schedule
                    )),
                });
            }

            seen_schedules.insert(schedule.clone());
        }
    }
}

/// Validate institution resource linking
pub fn validate_institution_resource_links(
    institution: &Institution,
    collector: &mut ErrorCollector,
) {
    // Check for duplicate behavior tree references
    if let Some(ref behavior_links) = institution.uses_behaviors {
        let mut seen_trees: HashSet<String> = HashSet::new();

        for link in behavior_links {
            let tree_name = link.tree.join("::");

            if seen_trees.contains(&tree_name) {
                collector.add(ResolveError::ValidationError {
                    message: format!(
                        "Institution '{}' has duplicate behavior tree reference: {}",
                        institution.name,
                        tree_name
                    ),
                    help: Some(format!(
                        "The behavior tree '{}' is referenced multiple times. Each behavior tree should only be referenced once.",
                        tree_name
                    )),
                });
            }

            seen_trees.insert(tree_name);
        }
    }

    // Check for duplicate schedule references
    if let Some(ref schedules) = institution.uses_schedule {
        let mut seen_schedules: HashSet<String> = HashSet::new();

        for schedule in schedules {
            if seen_schedules.contains(schedule) {
                collector.add(ResolveError::ValidationError {
                    message: format!(
                        "Institution '{}' has duplicate schedule reference: {}",
                        institution.name, schedule
                    ),
                    help: Some(format!(
                        "The schedule '{}' is referenced multiple times.",
                        schedule
                    )),
                });
            }

            seen_schedules.insert(schedule.clone());
        }
    }
}

/// Validate schedule composition requirements
///
/// Checks:
/// 1. All blocks in extended schedules have names
/// 2. Override blocks reference valid block names (requires name resolution)
pub fn validate_schedule_composition(schedule: &Schedule, collector: &mut ErrorCollector) {
    // If schedule extends another, all blocks must have names for override system
    if schedule.extends.is_some() {
        for block in &schedule.blocks {
            if block.name.is_none() && !block.activity.is_empty() {
                collector.add(ResolveError::ValidationError {
                    message: format!(
                        "Schedule '{}' extends another schedule but has unnamed blocks",
                        schedule.name
                    ),
                    help: Some(
                        "When a schedule extends another, all blocks must have names to support the override system. Use 'block name { ... }' syntax instead of 'time -> time : activity { ... }'.".to_string()
                    ),
                });
            }
        }
    }

    // Validate that new-style blocks have action references
    for block in &schedule.blocks {
        if block.name.is_some() && block.action.is_none() && block.activity.is_empty() {
            collector.add(ResolveError::ValidationError {
                message: format!(
                    "Schedule '{}' block '{}' missing action reference",
                    schedule.name,
                    block.name.as_ref().unwrap()
                ),
                help: Some(
                    "Named blocks should specify a behavior using 'action: BehaviorName'. Example: 'block work { 9:00 -> 17:00, action: WorkBehavior }'".to_string()
                ),
            });
        }
    }
}

/// Validate an entire file
///
/// Collects all validation errors and returns them together instead of failing
/// fast.
pub fn validate_file(file: &File, action_registry: &HashSet<String>) -> Result<()> {
    let mut collector = ErrorCollector::new();

    for decl in &file.declarations {
        match decl {
            | Declaration::Character(c) => {
                validate_trait_ranges(&c.fields, &mut collector);
                validate_character_resource_links(c, &mut collector);
            },
            | Declaration::Institution(i) => {
                validate_institution_resource_links(i, &mut collector);
            },
            | Declaration::Relationship(r) => {
                validate_relationship_bonds(std::slice::from_ref(r), &mut collector);
            },
            | Declaration::Schedule(s) => {
                validate_schedule_overlaps(s, &mut collector);
                validate_schedule_composition(s, &mut collector);
            },
            | Declaration::LifeArc(la) => {
                validate_life_arc_transitions(la, &mut collector);
            },
            | Declaration::Behavior(bt) => {
                validate_behavior_tree_actions(bt, action_registry, &mut collector);
            },
            | _ => {
                // Other declarations don't need validation yet
            },
        }
    }

    collector.into_result(())
}

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

    #[test]
    fn test_valid_trait_ranges() {
        let fields = vec![
            Field {
                name: "bond".to_string(),
                value: Value::Decimal(0.8),
                span: Span::new(0, 10),
            },
            Field {
                name: "age".to_string(),
                value: Value::Number(30),
                span: Span::new(0, 10),
            },
        ];

        let mut collector = ErrorCollector::new();
        validate_trait_ranges(&fields, &mut collector);
        assert!(!collector.has_errors());
    }

    #[test]
    fn test_invalid_bond_value_too_high() {
        let fields = vec![Field {
            name: "bond".to_string(),
            value: Value::Decimal(1.5),
            span: Span::new(0, 10),
        }];

        let mut collector = ErrorCollector::new();
        validate_trait_ranges(&fields, &mut collector);
        assert!(collector.has_errors());
    }

    #[test]
    fn test_invalid_bond_value_negative() {
        let fields = vec![Field {
            name: "bond".to_string(),
            value: Value::Decimal(-0.1),
            span: Span::new(0, 10),
        }];

        let mut collector = ErrorCollector::new();
        validate_trait_ranges(&fields, &mut collector);
        assert!(collector.has_errors());
    }

    #[test]
    fn test_invalid_age_negative() {
        let fields = vec![Field {
            name: "age".to_string(),
            value: Value::Number(-5),
            span: Span::new(0, 10),
        }];

        let mut collector = ErrorCollector::new();
        validate_trait_ranges(&fields, &mut collector);
        assert!(collector.has_errors());
    }

    #[test]
    fn test_invalid_age_too_high() {
        let fields = vec![Field {
            name: "age".to_string(),
            value: Value::Number(200),
            span: Span::new(0, 10),
        }];

        let mut collector = ErrorCollector::new();
        validate_trait_ranges(&fields, &mut collector);
        assert!(collector.has_errors());
    }

    #[test]
    fn test_valid_relationship_bond() {
        let relationship = Relationship {
            name: "Test".to_string(),
            participants: vec![],
            fields: vec![Field {
                name: "bond".to_string(),
                value: Value::Decimal(0.9),
                span: Span::new(0, 10),
            }],
            span: Span::new(0, 100),
        };

        let mut collector = ErrorCollector::new();
        validate_relationship_bonds(&[relationship], &mut collector);
        assert!(!collector.has_errors());
    }

    #[test]
    fn test_invalid_relationship_bond() {
        let relationship = Relationship {
            name: "Test".to_string(),
            participants: vec![],
            fields: vec![Field {
                name: "bond".to_string(),
                value: Value::Decimal(1.2),
                span: Span::new(0, 10),
            }],
            span: Span::new(0, 100),
        };

        let mut collector = ErrorCollector::new();
        validate_relationship_bonds(&[relationship], &mut collector);
        assert!(collector.has_errors());
    }

    #[test]
    fn test_life_arc_valid_transitions() {
        let life_arc = LifeArc {
            name: "Test".to_string(),
            states: vec![
                ArcState {
                    name: "start".to_string(),
                    on_enter: None,
                    transitions: vec![Transition {
                        to: "end".to_string(),
                        condition: Expr::Identifier(vec!["ready".to_string()]),
                        span: Span::new(0, 10),
                    }],
                    span: Span::new(0, 50),
                },
                ArcState {
                    name: "end".to_string(),
                    on_enter: None,
                    transitions: vec![],
                    span: Span::new(50, 100),
                },
            ],
            span: Span::new(0, 100),
        };

        let mut collector = ErrorCollector::new();
        validate_life_arc_transitions(&life_arc, &mut collector);
        assert!(!collector.has_errors());
    }

    #[test]
    fn test_life_arc_invalid_transition() {
        let life_arc = LifeArc {
            name: "Test".to_string(),
            states: vec![ArcState {
                name: "start".to_string(),
                on_enter: None,
                transitions: vec![Transition {
                    to: "nonexistent".to_string(),
                    condition: Expr::Identifier(vec!["ready".to_string()]),
                    span: Span::new(0, 10),
                }],
                span: Span::new(0, 50),
            }],
            span: Span::new(0, 100),
        };

        let mut collector = ErrorCollector::new();
        validate_life_arc_transitions(&life_arc, &mut collector);
        assert!(collector.has_errors());
    }

    #[test]
    fn test_behavior_tree_valid_actions() {
        let mut registry = HashSet::new();
        registry.insert("walk".to_string());
        registry.insert("eat".to_string());

        let tree = Behavior {
            name: "Test".to_string(),
            root: BehaviorNode::Sequence {
                label: None,
                children: vec![
                    BehaviorNode::Action("walk".to_string(), vec![]),
                    BehaviorNode::Action("eat".to_string(), vec![]),
                ],
            },
            span: Span::new(0, 100),
        };

        let mut collector = ErrorCollector::new();
        validate_behavior_tree_actions(&tree, &registry, &mut collector);
        assert!(!collector.has_errors());
    }

    #[test]
    fn test_behavior_tree_invalid_action() {
        // Create a registry with some actions (but not "unknown_action")
        let mut registry = HashSet::new();
        registry.insert("walk".to_string());
        registry.insert("work".to_string());

        let tree = Behavior {
            name: "Test".to_string(),
            root: BehaviorNode::Action("unknown_action".to_string(), vec![]),
            span: Span::new(0, 100),
        };

        let mut collector = ErrorCollector::new();
        validate_behavior_tree_actions(&tree, &registry, &mut collector);
        assert!(collector.has_errors());
    }
}